RESEARCH ARTICLESupport surfaces for pressure ulcerpre.docx

RESEARCH ARTICLE
Support surfaces for pressure ulcer
prevention: A network meta-analysis
Chunhu Shi
1*, Jo C. Dumville1, Nicky Cullum1,2
1 Division of Nursing, Midwifery & Social Work, School of
Health Sciences, Faculty of Biology, Medicine &
Health, University of Manchester, Manchester Academic Health
Science Centre, Manchester, United
Kingdom, 2 Research and Innovation Division, Manchester
University NHS Foundation Trust, Manchester
Academic Health Science Centre, Manchester, United Kingdom
* [email protected]
Abstract
Background
Pressure ulcers are a prevalent and global issue and support
surfaces are widely used for
preventing ulceration. However, the diversity of available
support surfaces and the lack of
direct comparisons in RCTs make decision-making difficult.

Objectives
To determine, using network meta-analysis, the relative effects
of different support surfaces
in reducing pressure ulcer incidence and comfort and to rank
these support surfaces in
order of their effectiveness.
Methods
We conducted a systematic review, using a literature search up
to November 2016, to iden-
tify randomised trials comparing support surfaces for pressure
ulcer prevention. Two review-
ers independently performed study selection, risk of bias
assessment and data extraction.
We grouped the support surfaces according to their
characteristics and formed evidence
networks using these groups. We used network meta-analysis to
estimate the relative
effects and effectiveness ranking of the groups for the outcomes
of pressure ulcer incidence
and participant comfort. GRADE was used to assess the
certainty of evidence.
Main results

We included 65 studies in the review. The network for assessing
pressure ulcer incidence
comprised evidence of low or very low certainty for most
network contrasts. There was mod-
erate-certainty evidence that powered active air surfaces and
powered hybrid air surfaces
probably reduce pressure ulcer incidence compared with
standard hospital surfaces (risk
ratios (RR) 0.42, 95% confidence intervals (CI) 0.29 to 0.63;
0.22, 0.07 to 0.66, respec-
tively). The network for comfort suggested that powered active
air-surfaces are probably
slightly less comfortable than standard hospital mattresses (RR
0.80, 95% CI 0.69 to 0.94;
moderate-certainty evidence).
PLOS ONE | https://doi.org/10.1371/journal.pone.0192707
February 23, 2018 1 / 29
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OPEN ACCESS
Citation: Shi C, Dumville JC, Cullum N (2018)
Support surfaces for pressure ulcer prevention: A
network meta-analysis. PLoS ONE 13(2):
e0192707. https://doi.org/10.1371/journal.
pone.0192707
Editor: Yih-Kuen Jan, University of Illinois at
Urbana-Champaign, UNITED STATES
Received: September 27, 2017
Accepted: January 29, 2018
Published: February 23, 2018
Copyright: © 2018 Shi et al. This is an open access
article distributed under the terms of the Creative
Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in
any medium, provided the original author and
source are credited.
Data Availability Statement: All relevant data are
within the paper and its Supporting Information

files.
Funding: This work was supported by a President’s
Doctoral Scholarship to CS from the University of
Manchester. The funder had no role in study
design, data collection and analysis, decision to
publish, or preparation of the manuscript. We also
received some analytical advice from the Complex
Reviews Support Unit, which is funded by the
National Institute for Health Research (project
number 14/178/29).
https://doi.org/10.1371/journal.pone.0192707
http://crossmark.crossref.org/dialog/?doi=10.1371/journal.pone.
0192707&domain=pdf&date_stamp=2018-02-23

http://creativecommons.org/licenses/by/4.0/
http://creativecommons.org/licenses/by/4.0/
Conclusions
This is the first network meta-analysis of the effects of support
surfaces for pressure ulcer
prevention. Powered active air-surfaces probably reduce
pressure ulcer incidence, but are
probably less comfortable than standard hospital surfaces. Most
prevention evidence was
of low or very low certainty, and more research is required to
reduce these uncertainties.
Introduction
Pressure ulcers are localised injuries to the skin and/or
underlying tissue, which are also
known as pressure injuries, pressure sores, decubitus ulcers and
bedsores [1]. Pressure ulcers
represent a serious heath burden with a point prevalence of
approximately 3.1 per 10,000 in
the United Kingdom (UK) [2]. It has been estimated that the
treatment of pressure ulcers costs
approximately 4% (between £1.4 and £2.1 billion) of the total
health budget of the UK (1999/
2000 financial year) [3].

Pressure ulcers are caused by localised pressure and shear [1],
thus intervention to alleviate
pressure and shear is an important part of pressure ulcer
prevention. Support surfaces (e.g.
mattresses, overlays, integrated bed systems) are designed to
work towards preventing pressure
ulcers primarily in this way [4]. Various types of support
surfaces have been developed with
different mechanisms for pressure and shear relief including (1)
redistributing the weight over
the maximum body surface area; (2) mechanically alternating
the pressure beneath body to
reduce the duration of the applied pressure [5]; or (3)
redistributing pressure by a combination
of the above, allowing health care professionals to change the
mode according to a person’s
needs [6]. Support surfaces are made from a variety of
construction materials (e.g. foam) and
have different functional features (e.g. low-air-loss) [4].
Identification of the optimum support
surface from the diverse options available requires evidence on
their relative effectiveness in
terms of how well they prevent the incidence of new pressure
ulcers [2].

Currently, seven systematic reviews containing meta-analyses
have summarised rando-
mised controlled trial (RCT) and quasi-randomised trial
evidence to inform choice of support
surface [7–13]. Of these reviews, one high-quality Cochrane
review includes all studies covered
by the remaining six reviews and offers the most comprehensive
summary of current evidence
[9]. However, all these reviews (including the Cochrane review
[9]) use an outdated support
surface classification systems [5] now superseded by the recent
internationally agreed NPUAP
Support Surface Standards Initiative (S3I) classification system
[4]. Additionally, the reviews
all use pairwise meta-analysis to synthesise evidence for head-
to-head comparisons of support
surfaces. There remains a lack of evidence on the relative
effects of different support surfaces,
in part due to a lack of head-to-head RCT data across the
plethora of treatment options
available.
To tackle this problem, an advanced meta-analysis technique,
network meta-analysis, can

be employed. The approach can simultaneously compare
multiple competing interventions in
a single statistical model whilst maintaining randomisation as
with standard meta-analysis
[14–16]. The network meta-analysis has the following
advantages. Firstly network meta-analy-
sis can produce “indirect evidence” for a potential comparison
where a head-to-head compari-
son is unavailable. A network can be developed to link the
direct evidence of, say, A vs. B and
B vs. C (i.e. evidence from studies with A vs. B and B vs. C as
head-to-head comparisons), via a
common comparator (i.e. B in this example) to derive an
indirect estimate of A vs. C. Sec-
ondly, both indirect and direct evidence can be used together
which then improves the
Support surfaces for pressure ulcer prevention
February 23, 2018 2 / 29
Competing interests: The authors have declared
that no competing interests exist.

precision of effect estimates. Thirdly, effect estimates from
network meta-analysis can be
linked to probabilistic modelling to allow the ranking of
treatments based on which is likely to
be the most effective for the outcome of interest, which is likely
to be the second best and so
on. This is a valuable approach for considering the results of the
network across multiple inter-
ventions in a single measure [14–16].
The aim of this work was to synthesise the available evidence
from RCTs in a network
meta-analysis to: (1) assess the relative effects of different
classes of support surfaces for reduc-
ing pressure ulcer incidence in adults in any setting; (2) to
assess the relative effects of different
classes of support surface in terms of reported comfort; and (3)
to rank all classes of support
surface in order of effectiveness regarding pressure ulcer
prevention.
Methods
This review was preceded by a protocol and registered
prospectively in PROSPERO
(CRD42016042154). This report complies with the relevant
PRISMA extension statement [17]

(see S1 File).
Search strategy
As the most comprehensive summary of available evidence in
the topic of our review, the cur-
rent Cochrane review had identified and included 59 RCTs and
quasi-randomised trials com-
paring support surfaces for pressure ulcer prevention, with a
database search up to April 2015
[9].
We performed an update search of the following databases for
the current Cochrane review:
the Cochrane Wounds Specialised Register (10 August 2016);
the Cochrane Central Register
of Controlled Trials (CENTRAL) (2016, Issue 7); Ovid
MEDLINE (1946 to 10 August 2016);
Ovid EMBASE (1974 to 10 August 2016); EBSCO CINAHL
Plus (1937 to 10 August 2016).
Additionally, we searched the Chinese Biomedical Literature
Database (1978 to 30 November
2016). There was no restriction on the basis of language or
publication status (see S2 File for
Ovid MEDLINE Search Strategy).

We also searched other resources: ClinicalTrials.gov and WHO
International Clinical Trials
Registry Platform (ICTRP) (24 August 2016), the Journal of
Tissue Viability via hand-search-
ing (1991 to November 2016), and the reference lists of seven
previously published systematic
reviews [7–13].
Eligibility criteria
We included published and unpublished RCTs, comparing
pressure-redistribution support
surfaces—mattresses, overlays, and integrated bed systems—in
adults at risk of pressure ulcer
development, in any setting. We excluded studies of seating and
cushions, limb protectors,
turning beds, traditional Chinese medicine-related surfaces and
home-made support surfaces.
Recent concern about the validity of RCTs from China led us to
only consider those with
full descriptions of robust randomisation methods (e.g. random
number tables) as eligible
[18, 19].
Our primary outcome was pressure ulcer incidence. We
considered this outcome as either

the proportion of participants developing a new ulcer at the
latest trial follow-up point (or the
pre-specified time point of primary focus if this was different to
the longest follow-up point)
or time-to-pressure ulcer incidence. The secondary outcome was
patient-reported comfort on
support surface (measured as the proportion of patients
reporting comfort).
February 23, 2018 3 / 29
Selection of studies
Two reviewers independently assessed the titles and abstracts of
the search results for relevance
and then independently inspected the full text of all potentially
eligible studies. Because the
non-Chinese database search was an updated search of the
Cochrane review published by
McInnes and colleagues [9], all studies included by the
Cochrane review were checked again
for relevance. Disagreements were resolved by discussion
between the two reviewers and

involvement of a third reviewer if necessary.
Data extraction
Where eligible studies had been previously included in McInnes
et al [9], one reviewer checked
the original data extraction of these studies and extracted
additional data where necessary, and
another reviewer checked all data. Two reviewers independently
extracted data for new
included studies. Any disagreements were resolved by
discussion and, if necessary, with the
involvement of a third reviewer. Where necessary, the authors
of included studies were con-
tacted to collect and/or clarify data.
The following data were extracted using a pre-prepared data
extraction form: basic charac-
teristics of studies (e.g. country, setting, and funding sources);
characteristics of participants
(including eligibility criteria, average age, proportions of
participants by gender, and partici-
pants’ baseline skin status); description of support surfaces and
details on any co-interven-
tions; number randomised, follow-up durations; drop-outs;
primary and secondary outcome

data.
In order to assign support surfaces to intervention groups, we
extracted full descriptions
from included studies where possible. However, when necessary
we supplemented the infor-
mation provided with that from external sources such as other
publications about the same
support surface, manufacturers’ and/or product websites and
expert clinical opinion [20].
Classification of interventions. Support surfaces in included
studies were classified using
the NPUAP system [4] and assigned to one of 14 intervention
groups [21] (see S3 File for the
detailed steps and Table 1 for the 14 intervention groups).
Risk of bias assessment
We used Cochrane’s Risk of Bias tool to assess risk of bias of
each included study [22]. For new
included studies, two reviewers independently assessed domain-
specific risk of bias [22]. For
studies included by McInnes and colleagues [9], previous
judgements were checked by two
reviewers independently and, where required, updated. Any
discrepancy between two review-

ers was resolved by discussion and a third reviewer where
necessary.
We then followed GRADE principles to summarise the overall
risk of bias across domains
for each included study [23]. After this, we applied the
approach proposed by Salanti and col-
leagues [24] to judge the overall risk of bias (referred to hereon
as “study limitations”) for
direct evidence (i.e. pairwise meta-analysis), network contrasts,
and the entire network. Three
categories were used to qualitatively rate study limitations: no
serious limitations; serious limi-
tations; and very serious limitation.
Data synthesis and analyses
We conducted all meta-analyses based on a frequentist
framework with a random effects
model [25]. All estimates are presented as risk ratios (RR) with
95% confidence intervals (CIs).
When presenting summaries of findings, we also calculated the
absolute risk of an event for a
specific intervention group compared with that for a standard
hospital surface. The baseline

February 23, 2018 4 / 29
risk used was the outcome on standard hospital surfaces (the
median risk across studies that
provided data for the outcome).
We performed pairwise meta-analyses in RevMan, calculated I-
squared (I
2
) measures and
visually inspected the forest plots to assess statistical
heterogeneity [26]. We then conducted
network meta-analysis in STATA1 (StataCorp. 2013) using
published network commands
Table 1. 14 intervention groups, explanations and selected
examples from included studies.
Intervention groups Reviewers’ explanations Selected examples
(with support surface brands if possible)
Powered/non-powered reactive
air surfaces
A group of support surfaces constructed of air-cells, which
redistribute body weight over a maximum surface area (i.e. has

reactive pressure redistribution mode), with or without the
requirement for electrical power
Static air mattress overlay, dry flotation mattress (e.g., Roho,
Sofflex), static air mattress (e.g., EHOB), and static mode of
Duo 2
mattress
Powered/non-powered reactive
low-air-loss air surfaces
A group of support surfaces made of air-cells, which have
reactive
pressure redistribution modes and a low-air-loss function, with
or without the requirement for electrical power
Low-air-loss Hydrotherapy
Powered reactive air-fluidised
surfaces
A group of support surfaces made of air-cells, which have
reactive
pressure redistribution modes and an air-fluidised function, with
the requirement for electrical power
Air-fluidised bed (e.g., Clinitron)

Non-powered reactive foam
surfaces
A group of support surfaces made of foam materials, which
have
a reactive pressure redistribution function, without the
Convoluted foam overlay (or pad), elastic foam overlay (e.g.,
Aiartex, microfluid static overlay), polyether foam pad, foam
mattress replacement (e.g. MAXIFLOAT), solid foam overlay,
viscoelastic foam mattress/overlay (e.g., Tempur, CONFOR-
Med,
Akton, Thermo)
Non-powered reactive fibre
surfaces
A group of support surfaces made of fibre materials, which have
a
reactive pressure redistribution function, without the
Silicore (e.g., Spenco) overlay/pad

Non-powered reactive gel
surfaces
A group of support surfaces made of gel materials, which have a
Gel mattress, gel pad used in operating theatre
Non-powered reactive
sheepskin surfaces
A group of support surfaces made of sheepskin, which have a
Australian Medical Sheepskins overlay
Non-powered reactive water
surfaces
A group of support surfaces based on water, which has the
capability of a reactive pressure redistribution function, without
the requirement for electrical power
Water mattress

Powered active air surfaces A group of support surfaces made of
air-cells, which
mechanically alternate the pressure beneath the body to reduce
the duration of the applied pressure (mainly via inflating and
deflating to alternately change the contact area between support
surfaces and the body) (i.e. alternating pressure (or active)
mode), with the requirement for electrical power
Alternating pressure-relieving air mattress (e.g., Nimbus II,
Cairwave, Airwave, MicroPulse), large-celled ripple
Powered active air surfaces and
non-powered reactive foam
surfaces
A group of support surfaces which use powered active air
surfaces
and non-powered reactive foam surfaces in combination
Alternating pressure-relieving air mattress in combination with
viscoelastic foam mattress/overlay (e.g., Nimbus plus Tempur)
Powered active low-air-loss air
surfaces

A group of support surfaces made of air-cells, which have the
capability of alternating pressure redistribution as well as low-
air-
loss for drying local skin, with the requirement for electrical
power
Alternating pressure low-air-loss air mattress
Powered hybrid system air
surfaces
A group of support surfaces made of air-cells, which offer both
reactive and active pressure redistribution modes, with the
Foam mattress with dynamic and static modes (e.g. Softform
Premier Active)
Powered hybrid system low-
air-loss air surfaces
A group of support surfaces made of air-cells, which offer both
reactive and active pressure redistribution modes as well as a
low-
air-loss function, with the requirement for electrical power

Stand-alone bed unit with alternating pressure, static modes and
low air-loss (e.g., TheraPulse)
Standard hospital surfaces A group of support surfaces made of
any materials, used as usual
in a hospital and without reactive nor active pressure
redistribution capabilities, nor any other functions (e.g. low-air-
loss, or air-fluidised).
Standard hospital (foam) mattress, NHS Contract hospital
mattress, standard operating theatre surface configuration,
standard bed unit and usual care
https://doi.org/10.1371/journal.pone.0192707.t001
February 23, 2018 5 / 29
and network graph packages [27, 28] (see S4 File for STATA
commands used in the review). A
consistency model was fitted to estimate relative effects [29].
Following this, we calculated the

relative rankings of intervention groups and presented the
surface under the cumulative rank-
ing curve (SUCRA) percentages [27]. For any outcome, we
performed network meta-analysis
only if intervention groups could be connected to form a
network; however, we did not
exclude comparisons of support surfaces assigned to the same
group from the overall system-
atic review. The full dataset is available on request.
We assessed the transitivity assumption for each network by
comparing the similarities of
study-level characteristics across direct comparisons within the
network [30]. When data were
insufficient for this assessment, we assumed that the transitivity
assumption was met. Inconsis-
tency between direct and indirect evidence was examined
globally by running the design-by-
treatment interaction model and locally by using the node-
splitting method and inconsistency
plot test [28, 31–33]. We also explored the sensitivity of the
global inconsistency finding to
alternative modelling approaches by running a post hoc
sensitivity analysis using the model of
Lu and Ades [34]. It is worth noting that because the model of

Lu and Ades [34] depends on
the ordering of treatments in the presence of multi-arm studies
[28] the design-by-treatment
interaction model was used in the main analysis. We then
evaluated the common network het-
erogeneity using the tau-squared (tau
2
) and the I
2
measure and the 95% CIs of I
2
, and decom-
posed the common network heterogeneity to inconsistency and
within-study heterogeneity in
R to locate the source of heterogeneity [35]. The heterogeneity
was considered as low, moder-
ate, or high if I
2
= 25%, 50%, or 75%, respectively [36].
When important inconsistency and/or heterogeneity occurred,
we followed steps proposed
by Cipriani and colleagues [37] to investigate further. Of these
steps, we performed pre-speci-
fied subgroup analyses for funding sources [38] and risk of bias

[39]; as well as four exploratory
sub-group analyses: setting, considering operating theatre as
setting or not, baseline skin sta-
tus, and follow-up duration. Additionally, we performed one
sensitivity analysis to assess the
impact of missing data (i.e. a complete case analysis for the
main analysis, followed by a
repeated analysis with missing data added to the denominator
but not the numerator) and
another one for the impact of unpublished studies by removing
them from the analysis.
Assessing the certainty of evidence
We assessed the potential for publication bias by considering
the completeness of the literature
search (i.e. inspecting the scope of the literature search, and
assessing the volume of unpub-
lished data located), and plotting the funnel plot for each
pairwise meta-analysis that included
more than 10 studies and a comparison-adjusted funnel plot for
the network [24, 27, 40]. To
obtain a meaningful comparison-adjusted funnel plot, we
ordered the intervention groups by
assuming that small studies are likely to favour advanced
support surfaces [27]. Finally, we fol-

lowed the GRADE approach proposed by Salanti and colleagues
[24] to assess the certainty of
evidence from the network meta-analysis for each network
contrast and the ranking of inter-
vention groups: the overall certainty could be rated from high,
moderate, low to very low.
Results
Search results
The search identified 2,816 records. Full-text screening of 108
potentially eligible studies led to
inclusion of 22 studies; eight published in English (one of the
eight was then associated with an
included study in the McInnes and colleagues’ review [9]) and
14 studies published in Chinese.
We also identified two on-going studies [41, 42]. In addition,
our rescreening of the 59 studies
included by McInnes and colleagues [9] identified 44 as
specifically eligible for this review. In
February 23, 2018 6 / 29

total therefore we included 65 studies in the review (see Fig 1,
and S5 File for a reference list of
included studies). Three were unpublished (one is a conference
abstract [43] and two are
research reports [44, 45].
Trial and study population characteristics
The characteristics of included studies are summarised in Table
2. The 65 studies enrolled a
total of 14,332 participants (median of study sample sizes: 100;
range: 10 to 1,972). Setting was
specified in 63 of 65 study reports (97%) and included accident
and emergency departments
and acute care, intensive care units, general medical wards,
orthopaedic centres, operating the-
atres, and long-term care settings (i.e. nursing homes, extended
care facilities, rehabilitation
wards, long-term units).
Fig 1. Flow diagram of included studies.
https://doi.org/10.1371/journal.pone.0192707.g001
February 23, 2018 7 / 29

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rt
o
n
S
c
a
le
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N
S
))
M
ic
ro
P
u
ls
e
(1
1
2
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v
s

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o
n
v
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n
ti
o
n
a
l
m
a
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a
g
e
m
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(1
0
5
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P
o
w
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d
a
c
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v
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a
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rf
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v
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a
n
d
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rd
h
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sp
it
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l
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rf
a
c
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In
d
u
st
ry
In
c
id
e
n
c
e

o
f
g
ra
d
e
I
to
IV
u
lc
e
rs
;
7
B
e
n
n
e
tt
1
9
9

8
(R
e
f
3
)
U
S
A
V
a
ri
o
u
s
w
a
rd
s
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.e
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tw
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o
r
m
o
re
w
a
rd
s)
1
1
6
(N
o
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P
a
ti
e
n
ts
in
c
o

n
ti
n
e
n
t
o
f
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ri
n
e
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d
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r
fa
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c
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s
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e
s)

;
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v
e
r
8
0
y
e
a
rs
o
n
a
v
e
ra
g
e
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4
5
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1
In
ta

c
t
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in
to
g
ra
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e
II
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lc
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r;
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ig
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H
y
d
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th
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ra
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y
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8

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v
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S
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8
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p
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c
&
in
d
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In
c
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f
g
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II
to
IV

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lc
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rs
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6
0
B
li
ss
1
9
6
7
(R
e
f
4
)
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K
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sp

it
a
l
in
g
e
n
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ra
l
8
3
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o
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e
n
e
ra
l
in
p

a
ti
e
n
ts
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e
s)
;
8
1
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4
;
2
7
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6
In
ta
c
t
sk
in

to
g
ra
d
e
II
u
lc
e
r;
A
t
ri
sk
(M
N
S
>
7
)
L
a
rg
e

-c
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ll
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d
R
ip
p
le
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2
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v
s
C
o
n
tr
o
l
(4
1
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P

o
w
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d
a
c
ti
v
e
a
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su
rf
a
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s
v
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st
a
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h
o
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it
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a
c
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P
u
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c
In
c
id
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n
c
e
o

f
p
re
ss
u
re
u
lc
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rs
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1
4
C
a
o
2
0
1
3
(R
e
f
5

)
†
C
h
in
a
In
te
n
si
v
e
c
a
re
u
n
it
s
8
3
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o
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U
e
ld
e
rl
y
p
a
ti
e
n
ts
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e
s)
;
8
2
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3
±
8
.0
1

;
6
8
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5
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
H

ig
h
ri
sk
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ra
d
e
n
<
1
2
)
气
垫
床
联
合
A
c
ti
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n
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ra

n
sl
a
ti
o
n
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ir
m
a
tt
re
ss
p
lu
s
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C
T
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N
m
a

tt
re
ss
)
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3
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v
s
气
垫
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ra
n
sl
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ti
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n
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m
a

tt
re
ss
)
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0
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a
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to
d
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fi
n
e
v
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le
to
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e
U
n
c
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a
r
In
c
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n
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f
p
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u
re
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lc
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2
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f
6
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ly
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0
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e
n
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ra
l
p
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ti
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n
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7
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4
0
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1

0
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ta
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to
g
ra
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e
I
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r;
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d
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sc
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lt
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ti
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g
p
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re
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2

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6
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s
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ta
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m
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4
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re
d
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c
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1
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h
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n
2
0
1
5
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f
7
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th
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tr
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9
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±
2
1
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;
1
0
4
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4
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n
c
le
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r;
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n
c
le
a
r

ri
sk
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绵
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和
可
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定
式
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绵
体
位
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ra
n
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ti
o
n
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o
a

m
p
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d
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1
2
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s
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定
式
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ra
n
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o
n
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l
p
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)
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6
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o
n
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o
w
e
re
d
re
a

c
ti
v
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l
su
rf
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v
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n
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n
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p
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d
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a
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a
m
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rf
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u
b
li
c
In
c
id
e
n
c

e
o
f
p
re
ss
u
re
u
lc
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rs
;
U
n
c
le
a
r
(C
on
tin
ue
d

)
February 23, 2018 8 / 29
T
a
b
le
2
.
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o
n
ti
n
u
e
d
)
C
o
b

b
1
9
9
7
(R
e
f
8
)
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S
A
V
a
ri
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u
s
w
a
rd
s
1

2
3
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o
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e
n
e
ra
l
p
a
ti
e
n
ts
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e
s)
;
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e
d

ia
n
6
4
;
7
0
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3
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc

e
rs
;
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ig
h
ri
sk
(B
ra
d
e
n
sc
a
le
)
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o
w
a
ir
lo
ss

b
e
d
(6
2
)
v
s
S
ta
ti
c
a
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m
a
tt
re
ss
o
v
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rl
a
y

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1
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w
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d
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n
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p
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a
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p
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In

c
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n
c
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f
p
re
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u
lc
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a
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p
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m
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p
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n
p
u
b
li
sh
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d
C
o

ll
ie
r
1
9
9
6
(R
e
f
9
)
¶
U
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G
e
n
e
ra
l
m
e
d

ic
a
l
w
a
rd
9
0
(N
o
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e
n
e
ra
l
p
a
ti
e
n
ts
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o
);
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o
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re
p
o
rt
e
d
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R
);
4
0
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9
U
n
c
le
a
r;

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n
c
le
a
r
ri
sk
S
e
v
e
n
fo
a
m
m
a
tt
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ss
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s
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1

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st
a
n
d
a
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sp
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l
m
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tt
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ss
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)
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w
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re
d
re
a
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ti
v
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m
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In
c
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c
e
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f
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u
lc
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c
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a
r
C
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n
in

e
1
9
9
0
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f
1
0
)
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a
n
a
d
a
E
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e
d

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8
7
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h
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ic
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l
d
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se
s
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e
s)
;
3
7
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6
±
1
3
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;
6
0

/8
8
N
o
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x
is
ti
n
g
p
re
ss
u
re
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lc
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rs
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sk
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o
rt
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sc
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le
)
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lt
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ti
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g
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p
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v
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rl
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y
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4
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w
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d
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ti
v
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a
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rf
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c
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s
v
s
n
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n
-
p
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w
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d
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a
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fi
b
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su

rf
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In
c
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n
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g
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to

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p
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u
lc
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9
0
C
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p
e
r
1
9
9
8

(R
e
f
1
1
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†
U
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O
rt
h
o
p
a
e
d
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1
0
0
(N
o
)
E

m
e
rg
e
n
c
y
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rt
h
o
p
a
e
d
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tr
a
u
m
a
(Y
e
s)
;
8

3
±
7
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5
;
1
6
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4
N
o
e
x
is
ti
n
g
p
re
ss
u
re

u
lc
e
rs
;
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t
ri
sk
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a
te
rl
o
w
sc
a
le
>
1
5
)
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ry

fl
o
ta
ti
o
n
m
a
tt
re
ss
(R
o
h
o
)
(4
9
)
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s
D
ry
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ta
ti
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n
m
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tt
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ss
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d

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n
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p
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d
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rf
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c
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s
p
o
w
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d
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n
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p
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w
e
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d
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a
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ti
v
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su
rf
a
c
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s
In
d
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st
ry
In
c
id
e
n
c
e
o
f
g
ra
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e

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to
IV
p
re
ss
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re
u
lc
e
rs
;
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ti
e
n
t
c
o
m
fo

rt
;
7
D
a
e
c
h
se
l
1
9
8
5
(R
e
f
1
2
)
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a
n
a
d
a

E
x
te
n
d
e
d
c
a
re
fa
c
il
it
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3
2
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o
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h
ro
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ic

n
e
u
ro
lo
g
ic
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l
c
o
n
d
it
io
n
s
(Y
e
s)
;
4
0
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5
±
1
3
.9
;
1
6
/1
6
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u

lc
e
rs
;
H
ig
h
ri
sk
A
lt
e
rn
a
ti
n
g
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re
ss
u
re
m
a

tt
re
ss
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6
)
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s
S
il
ic
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o
v
e
rl
a
y
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6
)
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o

w
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d
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
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o
n
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p
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e
re
d
re
a
c
ti
v
e
fi
b
re
su
rf
a
c
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s
P
u
b
li
c
&
in
d

u
st
ry
In
c
id
e
n
c
e
o
f
g
ra
d
e
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to
IV
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re
ss
u

re
u
lc
e
rs
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0
D
e
m
a
rr
e
2
0
1
2
(R
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f
1
3
)

†
B
e
lg
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m
V
a
ri
o
u
s
w
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rd
s
6
1
0
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e
s)
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e
n

e
ra
l
in
p
a
ti
e
n
ts
(Y
e
s)
;
7
6
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3
±
1
4
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2
;

2
4
1
/
3
6
9
In
ta
c
t
sk
in
to
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ra
d
e
I
u
lc
e
r;

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t
ri
sk
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ra
d
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sc
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le
)
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st
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g
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a
lt
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rn
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ti
n
g
p
re
ss
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re
a
ir
m
a
tt
re
ss
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9
8
)
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S

in
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lt
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2
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P
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p
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re
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lc
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ti
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t
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m
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1
4

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c
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n
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m
id
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s
1
9
9
5
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f
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4
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U
S
A
U
n

c
le
a
r
1
2
(N
o
)
G
ra
d
e
4
u
lc
e
rs
p
a
ti
e
n
ts
re

q
u
ir
in
g
m
y
o
c
u
ta
n
e
o
u
s
fl
a
p
c
lo
su
re
(N

o
);
4
0
.5
±
1
6
.2
9
;
1
1
/1
G
ra
d
e
IV
u
lc
e
rs
A

ir
-f
lu
id
is
e
d
C
li
n
it
ro
n
(6
)
v
s
R
o
h
o
d
ry
fl

o
ta
ti
o
n
m
a
tt
re
ss
(6
)
P
o
w
e
re
d
re
a
c
ti
v
e
a

ir
-f
lu
id
is
e
d
su
rf
a
c
e
s
v
s
p
o
w
e
re
d
/n
o
n
-

p
o
w
e
re
d
re
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
U
n
c
le
a

r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
r
(n
e
w
w
o
u

n
d
b
re
a
k
d
o
w
n
);
1
4
E
w
in
g
1
9
6
4
(R
e
f

1
5
)
¶
A
u
st
ra
li
a
G
e
ri
a
tr
ic
u
n
it
3
6
(N
o
)

G
e
n
e
ra
l
in
p
a
ti
e
n
ts
(N
o
);
7
2
.5
o
n
a
v
e
ra

g
e
;
N
R
U
n
c
le
a
r;
U
n
c
le
a
r
ri
sk
S
h
e
e
p

sk
in
s
(1
8
)
v
s
c
o
n
tr
o
l
(1
8
)
N
o
n
-p
o
w
e

re
d
re
a
c
ti
v
e
sh
e
e
p
sk
in
su
rf
a
c
e
s
v
s
st
a
n
d

a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
U
n
c
le
a
r
In
c
id
e
n

c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
1
8
0
F
e
u
c
h
ti
n

g
e
r
2
0
0
6
(R
e
f
1
6
)
G
e
rm
a
n
y
O
p
e
ra
ti
n

g
th
e
a
tr
e
1
7
5
(Y
e
s)
C
a
rd
ia
c
su
rg
e
ry
p
a
ti
e

n
ts
(Y
e
s)
;
6
7
.7
9
±
1
0
.9
;
1
2
5
/
5
0
In
ta
c

t
sk
in
to
g
ra
d
e
I
u
lc
e
r;
U
n
c
le
a
r
ri
sk
T
h
e

rm
o
(8
5
)
v
s
st
a
n
d
a
rd
o
p
e
ra
ti
n
g
th
e
a
tr
e

c
o
n
fi
g
u
ra
ti
o
n
(9
0
)
N
o
n
-p
o
w
e
re
d
re
a

c
ti
v
e
fo
a
m
su
rf
a
c
e
s
v
s
st
a
n
d
a
rd
h
o
sp
it
a

l
su
rf
a
c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss

u
re
u
lc
e
rs
;
5
(C
on
tin
ue
d
)
February 23, 2018 9 / 29
T
a
b
le

2
.
(C
o
n
ti
n
u
e
d
)
F
in
n
e
g
a
n
2
0
0
8
(R
e
f

1
7
)
¶
U
S
A
O
rt
h
o
p
a
e
d
ic
4
0
(N
o
)
P
a
ti
e

n
ts
re
q
u
ir
in
g
ti
ss
u
e
d
e
fi
c
it
re
p
a
ir
(Y
e
s)

;
5
5
.4
5
;
2
1
/1
2
U
lc
e
rs
N
IM
B
U
S
3
(1
9
)
v

s
A
ir
-f
lu
id
is
e
d
b
e
d
(2
1
)
P
o
w
e
re
d
a
c
ti
v

e
a
ir
su
rf
a
c
e
s
v
s
p
o
w
e
re
d
re
a
c
ti
v
e
a
ir

-f
lu
id
is
e
d
su
rf
a
c
e
s
In
d
u
st
ry
In
c
id
e
n
c
e
o

f
p
re
ss
u
re
u
lc
e
rs
;
P
a
ti
e
n
t
c
o
m
fo
rt
;
8

G
a
o
2
0
1
4
(R
e
f
1
8
)
C
h
in
a
H
o
sp
it
a
l
in

g
e
n
e
ra
l
9
6
(N
o
)
P
e
rs
is
te
n
t
v
e
g
e
ta
ti

v
e
st
a
te
p
a
ti
e
n
ts
(Y
e
s)
;
4
1
.3
8
±
3
.2
5
;
5

0
/4
6
U
n
c
le
a
r;
U
n
c
le
a
r
ri
sk
交
替
式
气
垫
床
(t
ra

n
sl
a
ti
o
n
:
A
lt
e
rn
a
ti
n
g
p
re
ss
u
re
a
ir
m
a

tt
re
ss
)
(4
8
)
v
s
普
通
床
垫
(t
ra
n
sl
a
ti
o
n
:
u
su

a
l
m
a
tt
re
ss
)
(4
8
)
P
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf

a
c
e
s
v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
U
n

c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
U

n
c
le
a
r
G
ra
y
1
9
9
4
(R
e
f
1
9
)
¶
U
K
V
a
ri

o
u
s
w
a
rd
s
1
7
0
(N
o
)
G
e
n
e
ra
l
o
rt
h
o
p

a
e
d
ic
p
a
te
n
ts
(Y
e
s)
;
7
5
.0
6
±
1
0
.3
1
;
6
6

/
1
0
4
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
A
t

ri
sk
(N
o
rt
o
n
sc
a
le
)
S
o
ft
fo
a
m
m
a
tt
re
ss
(9
0

)
v
s
S
ta
n
d
a
rd
h
o
sp
it
a
l
m
a
tt
re
ss
(8
0
)

N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s
v
s

st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
In
d
u
st
ry
In
c

id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
P
a
ti
e
n
t

c
o
m
fo
rt
;
1
0
G
ra
y
1
9
9
8
(R
e
f
2
0
)
†
¶
U

K
V
a
ri
o
u
s
w
a
rd
s
1
0
0
(N
o
)
G
e
n
e
ra
l
in

p
a
ti
e
n
ts
(Y
e
s)
;
6
5
±
5
.8
8
;
6
1
/3
9
N
o
e

x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
A
t
ri
sk
(N
o
rt
o
n

sc
a
le
)
T
ra
n
sf
o
a
m
w
a
v
e
(5
0
)
v
s
T
ra
n
sf

o
a
m
(5
0
)
N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su

rf
a
c
e
s
v
s
n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m

su
rf
a
c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u

re
u
lc
e
rs
;
P
a
ti
e
n
t
c
o
m
fo
rt
;
1
0
G
ra
y

2
0
0
8
(R
e
f
2
1
)
U
K
A
c
u
te
c
a
re
1
0
0
(N
o
)

G
e
n
e
ra
l
in
p
a
ti
e
n
ts
(N
o
);
8
3
.2
;
N
R
U
n

c
le
a
r;
H
ig
h
ri
sk
(N
o
rt
o
n
sc
a
le
)
S
o
ft
fo
rm

P
re
m
ie
r
A
c
ti
v
e
(5
0
)
v
s
a
lt
e
rn
a
ti
n
g
p
re

ss
u
re
a
ir
m
a
tt
re
ss
(5
0
)
P
o
w
e
re
d
h
y
b
ri
d

a
ir
su
rf
a
c
e
s
v
s
p
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf

a
c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u

lc
e
rs
;
U
n
c
le
a
r
G
u
n
n
in
g
b
e
rg
2
0
0
0
(R
e

f
2
2
)
S
w
e
d
e
n
A
c
c
id
e
n
t
a
n
d
e
m
e
rg

e
n
c
y
d
e
p
a
rt
m
e
n
t
&
w
a
rd
s
1
0
1
(Y
e
s)
S

u
sp
e
c
te
d
h
ip
fr
a
c
tu
re
p
a
ti
e
n
ts
(Y
e
s)
;
8
5

(6
6
to
1
0
2
);
8
1
/2
0
N
o
e
x
is
ti
n
g
p
re
ss
u
re

u
lc
e
rs
;
A
t
ri
sk
(M
N
S
<
.
2
1
)
V
is
c
o
-e
la

st
ic
fo
a
m
(4
8
)
v
s
S
ta
n
d
a
rd
h
o
sp
it
a
l
m
a
tt

re
ss
(5
3
)
N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf

a
c
e
s
v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
In
d

u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
1

4
H
a
m
p
to
n
1
9
9
7
(R
e
f
2
3
)
†
¶
U
K
U
n
c
le

a
r
7
5
(N
o
)
U
n
c
le
a
r
(N
o
);
7
7
o
n
a
v
e
ra

g
e
;
N
R
U
n
c
le
a
r;
U
n
c
le
a
r
ri
sk
A
lt
e
rn
a
ti

n
g
-p
re
ss
u
re
(C
a
ir
w
a
v
e
)
(3
6
)
v
s
A
lt
e
rn
a

ti
n
g
-p
re
ss
u
re
(A
ir
w
a
v
e
)
(3
9
)
P
o
w
e
re
d
a

c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
p
o
w
e
re
d
a
c
ti
v
e
a

ir
su
rf
a
c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss

u
re
u
lc
e
rs
;
2
0
H
o
fm
a
n
1
9
9
4
(R
e
f
2
4
)

N
e
th
e
rl
a
n
d
s
O
rt
h
o
p
a
e
d
ic
4
6
(Y
e
s)
F
e

m
o
ra
l-
n
e
c
k
fr
a
c
tu
re
p
a
ti
e
n
ts
(Y
e
s)
;
8
4

.4
2
±
7
.5
2
;
6
/3
8
In
ta
c
t
sk
in
to
g
ra
d
e
I
u

lc
e
r;
H
ig
h
ri
sk
(D
u
tc
h
sc
o
re
)
C
u
b
e
d
fo
a
m
(2

3
)
v
s
S
ta
n
d
a
rd
h
o
sp
it
a
l
m
a
tt
re
ss
(2
3
)

st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
U
n
c
le
a
r
In

c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
1
4
In
m
a
n

1
9
9
3
(R
e
f
2
5
)
C
a
n
a
d
a
In
te
n
si
v
e
c
a
re

u
n
it
s
1
0
0
(Y
e
s)
In
te
n
si
v
e
c
a
re
u
n
it
p
a

ti
e
n
ts
(Y
e
s)
;
6
4
.4
±
1
4
.1
9
;
5
1
/4
7
U
n
c

le
a
r;
A
t
ri
sk
L
o
w
-a
ir
-l
o
ss
(5
0
)
v
s
S
ta
n
d

a
rd
in
te
n
si
v
e
c
a
re
u
n
it
b
e
d
(5
0
)
P
o
w
e
re

d
/n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
lo
w
-a
ir
-l
o
ss

a
ir
su
rf
a
c
e
s
v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c

e
s
In
d
u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e

rs
;
1
7
(C
on
tin
ue
d
)
February 23, 2018 10 / 29
T
a
b
le
2
.
(C
o

n
ti
n
u
e
d
)
Ji
2
0
1
1
(R
e
f
2
6
)
C
h
in
a
H
o

sp
it
a
l
in
g
e
n
e
ra
l
6
0
(N
o
)
G
e
n
e
ra
l
p
a

ti
e
n
ts
(N
o
);
7
2
.3
(5
8
to
8
6
);
5
3
/3
7
N
o
e

x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
U
n
c
le
a
r
ri
sk
交

替
式
气
垫
床
(t
ra
n
sl
a
ti
o
n
:
A
lt
e
rn
a
ti
n
g
p
re
ss

u
re
a
ir
m
a
tt
re
ss
)
(3
0
)
v
s
医
院
标
准
普
通
泡
沫
海
绵
床
垫

(t
ra
n
sl
a
ti
o
n
:
S
ta
n
d
a
rd
h
o
sp
it
a
l
fo
a
m

m
a
tt
re
ss
)
(3
0
)
P
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a

c
e
s
v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
U
n
c

le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
2
8

Ji
a
n
g
2
0
1
5
(R
e
f
2
7
)
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h
in
a
V
a
ri
o
u
s

w
a
rd
s
1
0
7
4
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o
)
P
o
st
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p
e
ra
ti
v
e
p
a
ti
e

n
ts
(Y
e
s)
;
5
7
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4
±
1
5
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5
;
6
2
1
/
4
5
3

U
n
c
le
a
r;
H
ig
h
ri
sk
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ra
d
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n
sc
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1
3
o
n
a

v
e
ra
g
e
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态
空
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ra
n
sl
a
ti
o
n
:
A
lt
e
rn

a
ti
n
g
p
re
ss
u
re
a
ir
m
a
tt
re
ss
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1
2
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s
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ra
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ta
ti
c
a
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m
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tt
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6
2
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o
w
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d
a
c
ti
v
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w
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ir
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a
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rf
a
c
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v
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p
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w
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d
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p
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w
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d
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a
c

ti
v
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a
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a
c
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s
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n
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le
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r
In
c
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n
c
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o

f
p
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u
re
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lc
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rs
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n
c
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a
r
Jo
ll
e
y
2
0
0

4
(R
e
f
2
8
)
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u
st
ra
li
a
H
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sp
it
a
l
in
g
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ra
l
5
3
9
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e
s)
G
e
n
e
ra
l
in
p
a
ti
e
n
ts
(Y
e
s)

;
M
e
a
n
6
2
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4
(r
a
n
g
e
1
8
to
9
9
);
2
1
8
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2
3
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
L
o
w
to

m
o
d
e
ra
te
ri
sk
(B
ra
d
e
n
sc
a
le
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S
h
e
e
p
sk
in
(2

7
0
)
v
s
U
su
a
l
c
a
re
(2
6
9
)
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o
n
-p
o
w
e
re

d
re
a
c
ti
v
e
sh
e
e
p
sk
in
su
rf
a
c
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s
v
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st
a
n
d
a
rd

h
o
sp
it
a
l
su
rf
a
c
e
s
P
u
b
li
c
&
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d
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st
ry
In

c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
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n
c
le
a
r

K
e
m
p
1
9
9
3
(R
e
f
2
9
)
†
U
S
A
V
a
ri
o
u
s
w

a
rd
s
8
4
(N
o
)
G
e
n
e
ra
l
in
p
a
ti
e
n
ts
(Y
e
s)

;
8
1
±
8
;
2
6
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8
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u

lc
e
rs
;
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t
ri
sk
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ra
d
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n
sc
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le
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o
n
v
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lu
te

d
fo
a
m
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5
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s
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li
d
fo
a
m
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9
)
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o
n
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o

w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s
v
s
n
o
n
-

p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s
P
u
b
li
c

&
in
d
u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs

;
3
0
L
a
u
re
n
t
1
9
9
8
(R
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f
3
0
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e
lg
iu
m

In
te
n
si
v
e
c
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re
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n
it
3
1
2
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o
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a
rd
io
v
a
sc

u
la
r
su
rg
e
ry
p
a
ti
e
n
ts
(Y
e
s)
;
6
4
.0
±
1
1
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8
;
2
1
4
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8
U
n
c
le
a
r;
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n
c
le
a
r
ri
sk
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b
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s
a
n
d
T
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m
p
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r
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st
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t
lo
w
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re
ss

u
re
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7
)
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s
N
im
b
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s
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lt
e
rn
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ti
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g
p
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re
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te
n
si
v
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c
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n
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0
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T
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p
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r
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st
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n
t
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w
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st
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5
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ta
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d
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rd
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tt
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ss
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0
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w
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d
a
c
ti
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lu
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p
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re
d
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a
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fo
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m
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w
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p
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d
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a
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m
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a
l
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n
c
le
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r
In
c
id
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n
c
e
o
f
p
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ss
u
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u
lc
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c
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a
r
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fe
re
n
c
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n
p
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d
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to
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si
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L
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ra
1
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9
1
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f
3
1
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N
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in
g
h
o
m
e
6
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g
h
o
m
e
re
si
d
e

n
ts
(Y
e
s)
;
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3
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1
±
8
;
6
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1
U
lc
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rs
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t
ri

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v
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rl
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y
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e
l
m
a
tt
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ss
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3
)
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o
w
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d
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p
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w
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a
c
ti
v
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c
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v
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g
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rf
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In
d
u
st
ry
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c
id
e

n
c
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o
f
p
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ss
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lc
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8
0
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2
0
1
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f
3
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in
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H
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l
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2
0
0
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n
e
ra
l
p
a
ti
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ts
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o
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0
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4
±
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5
;
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1
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7
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n
c
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a
r;
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t
ri
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d

e
n
sc
a
le
)
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态
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sl
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ti
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:
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lt
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rn
a

ti
n
g
p
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re
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m
a
tt
re
ss
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0
0
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s
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态
空

气
垫
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ra
n
sl
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ti
o
n
:
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c
a
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m
a
tt
re
ss
)
(1
0

0
)
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o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a
c
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s
v
s
p
o

w
e
re
d
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o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
a
ir
su
rf
a

c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc

e
rs
;
U
n
c
le
a
r
(C
on
tin
ue
d
)
February 23, 2018 11 / 29
T
a
b
le

2
.
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o
n
ti
n
u
e
d
)
M
a
lb
ra
in
2
0
1
0
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e
f
3
3

)
B
e
lg
iu
m
In
te
n
si
v
e
c
a
re
u
n
it
1
6
(N
o
)
IC

U
p
a
ti
e
n
ts
re
q
u
ir
in
g
m
e
c
h
a
n
ic
a
l
v
e
n

ti
la
ti
o
n
(Y
e
s)
;
6
4
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±
1
5
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9
;
6
/1
0
U
lc

e
rs
;
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ig
h
ri
sk
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o
rt
o
n
sc
a
le
)
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S
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)
v
s
R
O
H
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D
R
Y
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L
O
A
T
A
T
IO
N
(8
)
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d
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c
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rf
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v
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w
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d
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n
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p
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w
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d
re
a
c
ti
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a
c
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s
In
d

u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
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u
lc
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rs
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n

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a
r
M
c
G
o
w
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n
2
0
0
0
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f
3
4
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u
st
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O
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2
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7
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s)
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o
p
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d

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p
a
ti
e
n
ts
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e
s)
;
7
3
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9
±
7
.8
8
;
1
2
7
/

1
7
0
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
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o
w

to
m
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d
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te
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sk
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d
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sc
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le
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h
e
e
p
sk
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5
5
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s
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n
tr
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l
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4
2
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n
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o
w
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d
re
a
c
ti
v
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sh
e
e
p
sk
in
su
rf
a
c
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s
v
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st
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h
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sp
it
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l
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rf
a
c
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s
P
u
b
li
c
&
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d
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st
ry

In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
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c
le
a
r

M
is
ti
a
e
n
2
0
0
9
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f
3
5
)
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e
th
e
rl
a
n
d
s

N
u
rs
in
g
h
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m
e
5
8
8
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e
s)
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e
n
e
ra
l
re
si
d

e
n
ts
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e
s)
;
7
8
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6
to
9
8
);
1
8
3
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0
5
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ra
d

e
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o
ri
sk
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ra
d
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n
sc
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1
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n
a
v
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ra
g
e

)
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h
e
e
p
sk
in
(2
9
5
)
v
s
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su
a
l
c
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re
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9
3
)

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n
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o
w
e
re
d
re
a
c
ti
v
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sh
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sk
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rf
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c

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In
c
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n
c
e
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f
p
re
ss
u
re
u
lc
e
rs
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3
0
N

ix
o
n
1
9
9
8
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f
3
6
)
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p
e
ra
ti
n
g
th
e

a
tr
e
4
4
6
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e
s)
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u
rg
e
ry
p
a
ti
e
n
ts
(Y
e
s)
;
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v
e
r
5
5
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e
a
rs
e
n
ro
ll
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d
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2
3
5
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0
8
In
ta

c
t
sk
in
to
g
ra
d
e
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u
lc
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r;
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n
c
le
a
r
ri
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is

c
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la
st
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p
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d
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2
2
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s
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d
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rd
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p
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ra

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n
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e
a
tr
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m
a
tt
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ss
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2
4
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o
n
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o
w
e

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d
re
a
c
ti
v
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fo
a
m
su
rf
a
c
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s
v
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st
a
n
d
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rd
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sp
it
a
l
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rf
a
c
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s
P
u
b
li
c
In
c
id
e
n
c
e
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f

p
re
ss
u
re
u
lc
e
rs
;
8
N
ix
o
n
2
0
0
6
(R
e
f
3
7

)
†
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K
V
a
ri
o
u
s
w
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rd
s
1
9
7
2
(Y
e
s)
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e
n

e
ra
l
p
a
ti
e
n
ts
(Y
e
s)
;
7
5
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±
9
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6
;
7
1
1
/1

2
6
0
In
ta
c
t
sk
in
to
g
ra
d
e
II
u
lc
e
r;
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n
c
le

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r
ri
sk
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lt
e
rn
a
ti
n
g
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re
ss
u
re
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v
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rl
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y
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9

0
)
v
s
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lt
e
rn
a
ti
n
g
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m
a
tt
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ss
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8

2
)
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o
w
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d
a
c
ti
v
e
a
ir
su
rf
a
c
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s
v
s
p
o

w
e
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d
a
c
ti
v
e
a
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su
rf
a
c
e
s
P
u
b
li
c
In
c
id
e

n
c
e
o
f
g
ra
d
e
II
to
IV
p
re
ss
u
re
u
lc
e
rs
;
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a
ti
e
n
t
c
o
m
fo
rt
;
6
0
O
z
y
u
re
k
2
0
1
5
(R
e

f
3
8
)
†
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u
rk
e
y
In
te
n
si
v
e
c
a
re
u
n
it
1
0

5
(N
o
)
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te
n
si
v
e
c
a
re
u
n
it
p
a
ti
e
n
ts
(Y
e
s)

;
6
4
.9
9
±
1
5
.1
8
;
N
R
In
ta
c
t
sk
in
to
g
ra
d

e
I
u
lc
e
r;
A
t
ri
sk
(B
ra
d
e
n
sc
a
le
<
1
8
)
V
is
c

o
e
la
st
ic
fo
a
m
1
(5
3
)
v
s
V
is
c
o
e
la
st
ic
fo
a
m

2
(5
2
)
N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf

a
c
e
s
v
s
n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su

rf
a
c
e
s
P
u
b
li
c
In
c
id
e
n
c
e
o
f
p
re
ss
u
re

u
lc
e
rs
;
7
P
ri
c
e
1
9
9
9
(R
e
f
3
9
)
U
K
O
rt

h
o
p
a
e
d
ic
8
0
(N
o
)
F
e
m
o
ra
l
n
e
c
k
fr
a
c
tu

re
d
p
a
ti
e
n
ts
(N
o
);
M
e
a
n
8
2
.2
(r
a
n
g
e
6
4

.4
to
9
8
.4
);
1
6
/6
4
U
n
c
le
a
r;
H
ig
h
ri
sk
(M
e
d

le
y
sc
o
re
>
2
5
)
R
e
p
o
se
(4
0
)
v
s
N
im
b
u
s

II
(4
0
)
P
o
w
e
re
d
/n
o
n
-
p
o
w
e
re
d
re
a
c
ti

v
e
a
ir
su
rf
a
c
e
s
v
s
p
o
w
e
re
d
a
c
ti
v
e
a
ir
su

rf
a
c
e
s
P
u
b
li
c
&
in
d
u
st
ry
In
c
id
e
n
c
e
o
f

p
re
ss
u
re
u
lc
e
rs
;
P
a
ti
e
n
t
c
o
m
fo
rt
(s
c

o
re
);
1
4
Q
u
2
0
1
4
(R
e
f
4
0
)
¶
C
h
in
a
N
e
u

ro
lo
g
ic
a
l
u
n
it
s
9
0
(N
o
)
G
e
n
e
ra
l
p
a
ti

e
n
ts
(Y
e
s)
;
5
6
.7
0
±
1
5
.6
1
;
6
3
/2
7
U
n

c
le
a
r;
A
t
ri
sk
(B
ra
d
e
n
sc
a
le
<
1
6
)
静
态
空
气
垫
(t

ra
n
sl
a
ti
o
n
:
S
ta
ti
c
a
ir
m
a
tt
re
ss
)
(4
5
)
v
s

动
态
空
气
垫
(t
ra
n
sl
a
ti
o
n
:
A
lt
e
rn
a
ti
n
g
p
re

ss
u
re
lo
w
-a
ir
-l
o
ss
a
ir
m
a
tt
re
ss
)
(4
5
)
N
o
n
-p

o
w
e
re
d
re
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
p
o
w
e

re
d
a
c
ti
v
e
lo
w
-a
ir
-l
o
ss
a
ir
su
rf
a
c
e
s
U
n
c
le

R
a
ft
e
r
2
0
1
1
(R
e
f
4
1
)
†
¶
U
K
R
e
h
a
b
il

it
a
ti
o
n
w
a
rd
s
1
0
(N
o
)
G
e
n
e
ra
l
p
a
ti
e

n
ts
(Y
e
s)
;
7
4
.9
;
N
R
In
ta
c
t
sk
in
to
g
ra
d
e

II
u
lc
e
r;
H
ig
h
ri
sk
(W
a
te
rl
o
w
sc
a
le
)
D
y
n
a
-F

o
rm
(5
)
v
s
S
o
ft
fo
rm
P
re
m
ie
r
A
c
ti
v
e
(5
)
P

o
w
e
re
d
h
y
b
ri
d
a
ir
su
rf
a
c
e
s
v
s
p
o
w
e
re

d
h
y
b
ri
d
a
ir
su
rf
a
c
e
s
In
d
u
st
ry
In
c
id
e
n
c

e
o
f
p
re
ss
u
re
u
lc
e
rs
;
P
a
ti
e
n
t
c
o
m
fo

rt
;
2
8
(C
on
tin
ue
d
)
February 23, 2018 12 / 29
T
a
b
le
2
.
(C
o
n

ti
n
u
e
d
)
R
ic
c
i
2
0
1
3
(R
e
f
4
2
)
†
¶
It
a
ly

L
o
n
g
-t
e
rm
u
n
it
s
5
0
(N
o
)
G
e
n
e
ra
l
in
p

a
ti
e
n
ts
(Y
e
s)
;
8
4
.7
±
7
.7
6
;
8
/4
2
In
ta
c

t
sk
in
to
g
ra
d
e
I
u
lc
e
r;
M
o
d
e
ra
te
to
h
ig
h
ri

sk
.
(B
ra
d
e
n
sc
a
le
)
A
ia
rt
e
x
(2
5
)
v
s
A
k
to
n

(2
5
)
N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c

e
s
v
s
n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf

a
c
e
s
In
d
u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc

e
rs
;
P
a
ti
e
n
t
c
o
m
fo
rt
;
2
8
R
u
ss
e
ll
2
0

0
0
(R
e
f
4
3
)
C
a
n
a
d
a
O
p
e
ra
ti
n
g
th
e
a
tr

e
1
9
8
(N
o
)
C
a
rd
io
th
o
ra
c
ic
su
rg
e
ry
p
a
ti
e

n
ts
(Y
e
s)
;
6
5
.2
±
1
0
.7
5
;
1
5
0
/4
8
N
o
e
x

is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
U
n
c
le
a
r
ri
sk
M
ic

ro
P
u
ls
e
(9
8
)
v
s
C
o
n
v
e
n
ti
o
n
a
l
c
a
re
(1

0
0
)
P
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
st
a

n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
In
d
u
st
ry
In
c
id
e

n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
7
R
u
ss
e
ll
2
0
0

3
(R
e
f
4
4
)
U
K
V
a
ri
o
u
s
w
a
rd
s
1
1
6
8
(Y

e
s)
G
e
n
e
ra
l
p
a
ti
e
n
ts
(Y
e
s)
;
8
3
(7
9
to
8
7

);
3
9
1
/7
7
7
U
n
c
le
a
r;
A
t
ri
sk
(W
a
te
rl
o
w

sc
a
le
)
C
O
N
F
O
R
-M
e
d
(5
6
4
)
v
s
S
ta
n
d
a
rd

m
a
tt
re
ss
(6
0
4
)
N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e

fo
a
m
su
rf
a
c
e
s
v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a

c
e
s
In
d
u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc

e
rs
;
P
a
ti
e
n
t
c
o
m
fo
rt
(s
c
o
re
);
1
1
S
a
n

a
d
a
2
0
0
3
(R
e
f
4
5
)
Ja
p
a
n
A
c
u
te
c
a
re
1

0
8
(N
o
)
P
a
ti
e
n
ts
n
e
e
d
in
g
to
b
e
b
e
d
b
o

u
n
d
w
it
h
h
e
a
d
e
le
v
a
te
d
(Y
e
s)
;
7
1
.2
6

±
1
2
.3
2
;
4
2
/
4
0
N
o
e
x
is
ti
n
g
p
re
ss
u
re

u
lc
e
rs
;
A
t
ri
sk
(B
ra
d
e
n
sc
a
le
)
D
o
u
b
le
&

si
n
g
le
-l
a
y
e
r
a
ir
o
v
e
rl
a
y
(7
3
)
v
s
S
ta
n
d

a
rd
h
o
sp
it
a
l
m
a
tt
re
ss
(3
5
)
P
o
w
e
re
d
a
c
ti

v
e
a
ir
su
rf
a
c
e
s
v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf

a
c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re

u
lc
e
rs
;
U
n
c
le
a
r
S
a
n
ty
1
9
9
4
(R
e
f
4
6
)

U
K
O
rt
h
o
p
a
e
d
ic
5
0
5
a
n
a
ly
se
d
(Y
e
s)
H
ip

fr
a
c
tu
re
p
a
ti
e
n
ts
(Y
e
s)
;
M
e
a
n
8
0
.2
3
(r
a

n
g
e
7
8
to
8
1
);
N
R
In
ta
c
t
sk
in
to
g
ra
d
e
II
u

lc
e
r;
A
t
ri
sk
(W
a
te
rl
o
w
sc
a
le
)
F
o
u
r
fo
a
m

m
a
tt
re
ss
e
s
(4
4
1
)
v
s
N
H
S
C
o
n
tr
a
c
t
(6
4

)
N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s

v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
P
u
b
li
c
In

c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
1
2
R
e
se

a
rc
h
re
p
o
rt
;
u
n
p
u
b
li
sh
e
d
S
c
h
u
lt
z
1

9
9
9
(R
e
f
4
7
)
U
S
A
O
p
e
ra
ti
n
g
th
e
a
tr
e

4
1
3
(Y
e
s)
S
u
rg
e
ry
p
a
ti
e
n
ts
(Y
e
s)
;
6
5
.7
1

±
1
2
.2
8
;
2
6
6
/1
4
7
N
o
e
x
is
ti
n
g
p
re
ss
u

re
u
lc
e
rs
;
U
n
c
le
a
r
ri
sk
E
x
p
e
ri
m
e
n
ta
l

m
a
tt
re
ss
o
v
e
rl
a
y
(2
0
6
)
v
s
U
su
a
l
c
a
re
(2
0

7
)
N
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e

s
v
s
st
a
n
d
a
rd
h
o
sp
it
a
l
su
rf
a
c
e
s
P
u
b
li

c
&
in
d
u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e

rs
;
6
S
id
e
ra
n
k
o
1
9
9
2
(R
e
f
4
8
)
U
S
A
In

te
n
si
v
e
c
a
re
u
n
it
5
7
(N
o
)
In
te
n
si
v
e
c
a
re

u
n
it
p
a
ti
e
n
ts
(Y
e
s)
;
6
5
.8
5
±
1
4
.6
9
;
3

3
/2
4
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
U
n

c
le
a
r
ri
sk
A
lt
e
rn
a
ti
n
g
a
ir
m
a
tt
re
ss
(2
0
)
v

s
S
ta
ti
c
a
ir
m
a
tt
re
ss
(2
0
)
v
s
W
a
te
r
m
a
tt
re

ss
(1
7
)
P
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s

p
o
w
e
re
d
/n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
a
ir
su

rf
a
c
e
s
v
s
n
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e
w
a
te

r
su
rf
a
c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss

u
re
u
lc
e
rs
;
U
n
c
le
a
r
T
h
re
e
-a
rm
R
C
T
S
ta

p
le
to
n
1
9
8
6
(R
e
f
4
9
)
U
K
O
rt
h
o
p
a
e
d

ic
1
0
0
(N
o
)
N
e
c
k
fe
m
u
r
fr
a
c
tu
re
d
p
a
ti
e
n

ts
(Y
e
s)
;
8
1
o
n
a
v
e
ra
g
e
;
0
/8
1
N
o
e
x
is
ti

n
g
p
re
ss
u
re
u
lc
e
rs
;
A
t
ri
sk
(N
o
rt
o
n
sc
o

re
<
1
4
)
L
a
rg
e
C
e
ll
R
ip
p
le
(3
2
)
v
s
S
p
e

n
c
o
p
a
d
(3
4
)
v
s
P
o
ly
e
th
e
r
fo
a
m
p
a
d
(3
4

)
P
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
n
o
n

-
p
o
w
e
re
d
re
a
c
ti
v
e
fi
b
re
su
rf
a
c
e
s
v
s
n
o

n
-p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s
P
u
b

li
c
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
U
n
c

le
a
r
T
h
re
e
-a
rm
R
C
T
T
a
k
a
la
1
9
9
6
(R
e
f

5
0
)
F
in
la
n
d
In
te
n
si
v
e
c
a
re
u
n
it
4
0
(N
o

)
In
te
n
si
v
e
c
a
re
u
n
it
p
a
ti
e
n
ts
(Y
e
s)
;
6
1

.4
2
±
1
4
.3
2
;
2
5
/1
5
U
n
c
le
a
r;
U
n
c
le
a
r

ri
sk
C
a
ri
ta
l
O
p
ti
m
a
(2
1
)
v
s
S
ta
n
d
a
rd
h

o
sp
it
a
l
fo
a
m
m
a
tt
re
ss
(1
9
)
P
o
w
e
re
d
/n
o
n

-
p
o
w
e
re
d
re
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
st
a

n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
1
4
(C
on
tin
ue
d
)

February 23, 2018 13 / 29
T
a
b
le
2
.
(C
o
n
ti
n
u
e
d
)
T
a
n
g
2

0
1
4
(R
e
f
5
1
)
†
C
h
in
a
In
te
n
si
v
e
c
a
re
u

n
it
8
0
0
(N
o
)
In
te
n
si
v
e
c
a
re
u
n
it
p
a
ti
e

n
ts
(Y
e
s)
;
7
2
.0
±
2
.1
;
4
4
1
/3
5
9
N
o
e
x
is

ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
H
ig
h
ri
sk
(B
ra
d
e
n
sc

o
re
<
1
2
)
防
压
疮
气
垫
床
(t
ra
n
sl
a
ti
o
n
:
A
n
ti
-

u
lc
e
r
a
ir
m
a
tt
re
ss
)
(4
0
5
)
v
s
理
疗
充
气
床
垫
辅
以

患
者
换
床
单
(t
ra
n
sl
a
ti
o
n
:
P
h
y
si
o
th
e
ra
p
y
a

ir
m
a
tt
re
ss
p
lu
s
re
p
la
c
e
m
e
n
t
sh
e
e
ts
)
(3
9

5
)
U
n
a
b
le
to
d
e
fi
n
e
v
s
u
n
a
b
le
to
d
e
fi

n
e
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc

e
rs
;
U
n
c
le
a
r
T
a
y
lo
r
1
9
9
9
(R
e
f
5
2
)
�

U
K
A
c
u
te
c
a
re
se
tt
in
g
4
4
(Y
e
s)
G
e
n
e
ra
l
in
p

a
ti
e
n
ts
(Y
e
s)
;
6
8
.3
8
±
3
.1
1
;
2
5
/1
9
N
o

e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
A
t
ri
sk
P
e
g
a

su
s
T
ri
n
o
v
a
(2
2
)
v
s
A
lt
e
rn
a
ti
n
g
p
re
ss

u
re
a
ir
m
a
tt
re
ss
(2
2
)
P
o
w
e
re
d
h
y
b
ri
d
a
ir

su
rf
a
c
e
s
v
s
p
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a
c
e

s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e

rs
;
U
n
c
le
a
r
T
h
e
a
k
e
r
2
0
0
5
(R
e
f
5
3
)

U
K
In
te
n
si
v
e
c
a
re
u
n
it
6
2
(Y
e
s)
In
te
n
si
v

e
c
a
re
u
n
it
p
a
ti
e
n
ts
(Y
e
s)
;
6
5
(2
6
to
8
5

);
3
9
/2
3
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
H

ig
h
ri
sk
T
h
e
ra
P
u
ls
e
(3
0
)
v
s
H
il
l-
R
o
m
D

u
o
(3
2
)
P
o
w
e
re
d
h
y
b
ri
d
lo
w
a
ir
lo
ss
su
rf

a
c
e
s
v
s
p
o
w
e
re
d
h
y
b
ri
d
a
ir
su
rf
a
c
e
s
U

n
c
le
a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;

1
4
V
a
n
d
e
rw
e
e
2
0
0
5
(R
e
f
5
4
)
B
e
lg
iu
m

V
a
ri
o
u
s
w
a
rd
s
4
4
7
(Y
e
s)
G
e
n
e
ra
l
p
a
ti

e
n
ts
(Y
e
s)
;
8
1
.5
(7
6
to
8
8
);
1
6
4
/2
8
3
In

ta
c
t
sk
in
to
g
ra
d
e
I
u
lc
e
r;
A
t
ri
sk
(B
ra
d
e
n

sc
o
re
<
1
7
)
A
lt
e
rn
a
ti
n
g
p
re
ss
u
re
a
ir
m
a

tt
re
ss
(2
2
2
)
v
s
V
is
c
o
-e
la
st
ic
fo
a
m
m
a
tt
re
ss

(2
2
5
)
P
o
w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s

n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s
P

u
b
li
c
&
in
d
u
st
ry
In
c
id
e
n
c
e
o
f
g
ra
d
e
II

to
IV
p
re
ss
u
re
u
lc
e
rs
;
U
n
c
le
a
r
v
a
n
L
e
e
n

2
0
1
1
(R
e
f
5
5
)
N
e
th
e
rl
a
n
d
s
N
u
rs
in
g

h
o
m
e
8
3
(Y
e
s)
N
u
rs
in
g
h
o
m
e
re
si
d
e
n
ts

(Y
e
s)
;
8
2
.0
9
±
8
.1
8
;
1
6
/6
7
N
o
e
x
is
ti
n

g
p
re
ss
u
re
u
lc
e
rs
;
H
ig
h
ri
sk
(N
o
rt
o
n
sc
o

re
<
1
2
)
S
ta
ti
c
a
ir
o
v
e
rl
a
y
(4
2
)
v
s
S
ta

n
d
a
rd
h
o
sp
it
a
l
m
a
tt
re
ss
(4
1
)
P
o
w
e
re
d
/n

o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s

c
id
e
n
c
e
o
f
g
ra
d
e
II
to
IV
p
re
ss
u
re
u
lc
e
rs

;
1
8
0
v
a
n
L
e
e
n
2
0
1
3
(R
e
f
5
6
)
N
e
th
e

rl
a
n
d
s
N
u
rs
in
g
h
o
m
e
4
1
(N
o
)
N
u
rs
in
g

h
o
m
e
re
si
d
e
n
ts
(Y
e
s)
;
7
9
.9
7
;
9
/3
2
N
o

e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
M
e
d
iu
m
to
h
ig

h
ri
sk
(B
ra
d
e
n
sc
o
re
6
to
1
9
)
S
ta
ti
c
a
ir
o
v
e

rl
a
y
(2
0
)
v
s
V
is
c
o
e
la
st
ic
fo
a
m
m
a
tt
re
ss

(2
1
)
P
o
w
e
re
d
/n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e

a
ir
su
rf
a
c
e
s
v
s
n
o
n
-p
o
w
e
re
d
re
a
c
ti
v
e

fo
a
m
su
rf
a
c
e
s
U
n
c
le
a
r
In
c
id
e
n
c
e
o
f
g

ra
d
e
II
to
IV
p
re
ss
u
re
u
lc
e
rs
;
1
8
0
C
ro
ss
-o

v
e
r
d
e
si
g
n
(d
a
ta
a
t
th
e
fi
rs
t
p
h
a
se
c
o
ll
e

c
te
d
)
V
e
rm
e
tt
e
2
0
1
2
(R
e
f
5
7
)
C
a
n
a
d

a
V
a
ri
o
u
s
w
a
rd
s
1
1
0
(Y
e
s)
G
e
n
e
ra
l
p

a
ti
e
n
ts
(Y
e
s)
;
7
7
.8
±
1
2
.7
6
;
4
4
/6
6
N
o

e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
M
o
d
e
ra
te
to
v
e

ry
h
ig
h
ri
sk
(B
ra
d
e
n
sc
o
re
<
1
4
)
In
fl
a
te
d
st

a
ti
c
o
v
e
rl
a
y
(5
5
)
v
s
M
ic
ro
fl
u
id
st
a
ti
c
o

v
e
rl
a
y
(5
0
)
P
o
w
e
re
d
/n
o
n
-
p
o
w
e
re
d

re
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
n
o
n
-p
o
w
e
re
d

re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s
N
o
In
c
id
e
n
c
e
o
f

p
re
ss
u
re
u
lc
e
rs
;
P
a
ti
e
n
t
c
o
m
fo
rt
;
1

4
V
y
h
li
d
a
l
1
9
9
7
(R
e
f
5
8
)
†
U
S
A
N
u
rs

in
g
h
o
m
e
s
4
0
(N
o
)
G
e
n
e
ra
l
p
a
ti
e
n
ts

(Y
e
s)
;
7
7
.2
±
1
4
.2
1
;
1
8
/2
2
N
o
e
x
is
ti
n

g
p
re
ss
u
re
u
lc
e
rs
;
A
t
ri
sk
(B
ra
d
e
n
sc
o
re
<

1
8
)
IR
IS
3
0
0
0
(2
0
)
v
s
M
A
X
IF
L
O
A
T
(2
0

v
s
n
o
n
-
p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e

s
In
d
u
st
ry
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs

;
2
1
(C
on
tin
ue
d
)
February 23, 2018 14 / 29
T
a
b
le
2
.
(C
o
n

ti
n
u
e
d
)
W
a
n
g
2
0
1
6
(R
e
f
5
9
)
C
h
in
a

In
te
n
si
v
e
c
a
re
u
n
it
1
6
0
(N
o
)
C
a
rd
io
th
o
ra

c
ic
su
rg
e
ry
p
a
ti
e
n
ts
(Y
e
s)
;
5
3
.5
4
±
1
1
.2

8
;
9
0
/7
0
N
o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;

A
t
ri
sk
(B
ra
d
e
n
sc
o
re
<
1
6
)
自
动
压
力
交
替
床
垫
(t
ra

n
sl
a
ti
o
n
:
A
u
to
m
a
ti
c
a
ll
y
a
lt
e
rn
a
ti

n
g
p
re
ss
u
re
a
ir
m
a
tt
re
ss
)
(8
0
)
v
s
交
替
式
减
压
床

垫
(t
ra
n
sl
a
ti
o
n
:
A
lt
e
rn
a
ti
n
g
p
re
ss
u
re

re
li
e
v
in
g
a
ir
m
a
tt
re
ss
)
(8
0
)
P
o
w
e
re
d
h
y

b
ri
d
a
ir
su
rf
a
c
e
s
v
s
p
o
w
e
re
d
a
c
ti
v
e
a
ir

re
u
lc
e
rs
;
U
n
c
le
a
r
W
e
i
2
0
1
6
(R
e
f
6
0

)
C
h
in
a
In
te
n
si
v
e
c
a
re
u
n
it
6
0
(N
o
)
C
o

m
a
p
a
ti
e
n
ts
(Y
e
s)
;
6
9
.8
0
±
8
.3
5
;
N
R
N

o
e
x
is
ti
n
g
p
re
ss
u
re
u
lc
e
rs
;
H
ig
h
ri
sk
(B
ra

d
e
n
sc
o
re
<
1
2
)
常
规
护
理
和
气
垫
床
(t
ra
n
sl
a
ti
o
n

:
A
ir
su
rf
a
c
e
s
p
lu
s
u
su
a
l
c
a
re
s)
(3
0
)
v
s

常
规
护
理
(t
ra
n
sl
a
ti
o
n
:
U
su
a
l
c
a
re
s)
(3
0
)
P
o

w
e
re
d
a
c
ti
v
e
a
ir
su
rf
a
c
e
s
v
s
st
a
n
d
a
rd
h

p
re
ss
u
re
u
lc
e
rs
;
U
n
c
le
a
r
W
h
it
n
e
y
1
9

8
4
(R
e
f
6
1
)
U
S
A
H
o
sp
it
a
l
in
g
e
n
e
ra
l

5
1
(N
o
)
G
e
n
e
ra
l
p
a
ti
e
n
ts
(N
o
);
6
3
.2

(1
9
to
9
1
);
N
R
E
x
is
ti
n
g
sk
in
b
re
a
k
d
o
w
n

;
U
n
c
le
a
r
ri
sk
A
lt
e
rn
a
ti
n
g
-p
re
ss
u
re
m

a
tt
re
ss
(2
5
)
v
s
C
o
n
v
o
lu
te
d
fo
a
m
p
a
d
(2
6

-
p
o
w
e
re
d
re
a
c
ti
v
e
fo
a
m
su
rf
a
c
e
s
U
n
c
le

a
r
In
c
id
e
n
c
e
o
f
p
re
ss
u
re
u
lc
e
rs
;
8
X
u

2
0
1
5
(R
e
f
6
2
)
†
C
h
in
a
H
o
sp
it
a
l
in
g
e

n
e
ra
l
7
6
(N
o
)
G
e
n
e
ra
l
p
a
ti
e
n
ts
(Y
e
s)

;
6
7
.4
5
±
2
.7
5
;
4
1
/3
5
N
o
e
x
is
ti
n
g
p
re

ss
u
re
u
lc
e
rs
;
H
ig
h
ri
sk
(B
ra
d
e
n
sc
o
re
<
1
2

)
喷
气
式
防
压
疮
垫
(t
ra
n
sl
a
ti
o
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;
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ra
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a
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m
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床
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ra

n
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2
February 23, 2018 15 / 29
The average age of participants was specified for 64 studies
(98%) and ranged from 37 to 85
years (median: 70 years). Gender was specified for 57 studies
(with 13,158 participants), within
these 53% of participants were female. Forty included studies
(62%) recruited only participants
with intact skin at baseline and/or those with grade I ulcers. Ten
studies (15%) enrolled partici-
pants with existing ulcers (recorded or assumed to be grade II or
above). In the 44 studies
(68%) that clearly stated duration of follow-up the median was
14 days (range: 5 to 180). There
were 23 studies (35%) that were completely or partly funded by
industry and 15 studies (23%)
supported by public funding.
In terms of intervention groups, of 65 studies, four (6%) used
support surfaces that were

impossible to classify into an intervention group due to
insufficient detail; and an additional
11 studies (17%) compared support surfaces within the same
intervention groups (see
Table 2). These 15 studies were removed from quantitative
analysis because their intervention
groups were unconnected to any network although they are still
included in the review.
Risk of bias assessment
Of 65 studies, 28 studies (43%) were judged to have no serious
limitations; and the remaining
37 studies (57%) had serious or very serious limitations (see S6
File).
Network meta-analysis
We conducted two main network meta-analyses; the first for
pressure ulcer incidence (the Pre-
vention Network) and the second for patient comfort (the
Comfort Network). No network
was formed for time-to- pressure ulcer incidence because the
eight (12%) studies (Refs 13, 28,
34, 35, 37, 53, 54, 58 in the Table 2) with available outcome
data did not form a network con-
necting more than two intervention groups.

Prevention network: Summary of included evidence. All 65
included studies reported
the outcome of pressure ulcer incidence, of which 20 were
excluded from analysis: three
reporting zero events in both arms (Refs 9, 17, 40 in the Table
2) (see Discussion for further
consideration of these three studies), six with incomplete
outcome data and intervention
descriptions (Refs 5, 15, 19, 51, 63, 64 in the Table 2), and 11
comparing support surfaces from
the same intervention groups (Refs 11, 13, 20, 23, 29, 37, 38,
41, 42, 58, 62 in the Table 2) (see
Table 2). Of the remaining 45 studies, 43 were included in the
main analysis and two (Refs 2
and 52 in the Table 2) were only considered in the sensitivity
analysis imputing missing data.
The 43 studies (Ref 1, 3, 4, 6–8, 10, 12, 14, 16, 18, 21, 22, 24–
28, 30–36, 39, 43–50, 53–57, 59–
61, 65 in Table 2), involved 9,430 participants and formed 24
direct comparisons and a net-
work of 14 intervention groups.
Prevention network: Main findings. The results of the pairwise
and network meta-analy-

ses are summarised in Fig 3 along with the GRADE certainty of
evidence assessment for the
network meta-analysis (see S7 File for pairwise meta-analyses;
see S9 File for GRADE assess-
ment). Of the 24 direct comparisons, 12 (50%) were judged to
have serious or very serious lim-
itations (see Fig 2). The entire network was considered to have
serious study limitations.
Additionally, the network was considered to be sparse as 13 of
the 24 direct links were only
informed by one study in each case.
The analysis results suggest that powered hybrid low-air-loss
air surfaces have the highest
probability of being the most effective intervention (SUCRA =
87.4%). However we remain
uncertain as to the true ranking of these treatments because the
certainty of evidence was very
low (see Fig 3 and S9 File).
Overall, the evidence regarding the relative effects of support
surfaces on pressure ulcer
development is of low or very low certainty for 89 of the 91
network contrasts in the network.

February 23, 2018 16 / 29
We present a further narrative summary of the network meta-
analysis findings for what are
considered key comparisons: the 13 intervention groups
compared with standard hospital
surfaces.
There is moderate certainty evidence that powered active air
surfaces and powered hybrid
air surfaces probably reduce the incidence of pressure ulcers
compared with standard hospital
surfaces (the latter having an assumed baseline risk of 219 per
1,000 participants) (RR 0.42,
95% CI 0.29 to 0.63; and RR 0.22, 95% CI 0.07 to 0.66,
respectively). This represents 127 fewer
people developing new ulcers per 1,000 (95% CI 81 to 155 per
1000) on powered active air sur-
faces and 171 fewer people developing new ulcers per 1,000
(95% CI 74 to 204) on powered
hybrid air surfaces than on standard hospital surfaces. There is
low-certainty evidence that
non-powered reactive fibre surfaces, non-powered reactive

water surfaces, powered hybrid
low-air-loss air surfaces, and powered/non-powered reactive air
surfaces may reduce pressure
ulcer incidence compared with standard hospital surfaces. It is
uncertain whether the remain-
ing seven intervention groups reduce the incidence of pressure
ulcers compared with standard
hospital surfaces as the evidence is of very low certainty.
Prevention network: Results of transitivity assessment and
heterogeneity analyses.
We deemed that the transitivity assumption held and there was
no suggestion of global
Fig 2. Network plot for the incidence of pressure ulcers
produced by STATA networkplot command. Fourteen
intervention groups are coded in the plot (i.e., nodes): SC =
standard hospital surfaces, npReFibre = non-powered
reactive fibre surfaces, npReFoam = non-powered reactive foam
surfaces, npReGel = non-powered reactive gel
surfaces, npReSheepskin = non-powered reactive sheepskin
surfaces, npReWater = non-powered reactive water
surfaces, pActAir = powered active air-cells surfaces,
pActAirnpReFoam = powered active air-cells surfaces plus non-
powered reactive foam surfaces, pActLAL = powered active
low-air-loss air surfaces, pHybridAir = powered hybrid

air-cells surfaces, pHybridLAL = powered hybrid low-air-loss
air surfaces, pReAirfluid = powered reactive air-fluidised
surfaces, pnpReAir = powered or non-powered reactive air-cells
surfaces, and pnpReLAL = powered or non-powered
reactive low-air-loss air surfaces. Each node size is proportional
to the number of direct comparisons involving each
intervention group. Taking any two of the six nodes forms 91
network contrasts. 24 lines between nodes represent
direct comparisons driven by RCTs; and line thickness is
proportional to the number of studies involved in each direct
comparison. Direct evidence of two or more comparisons can
generate indirect evidence for contrasts that did not
involve a head-to-head RCT (e.g., indirect evidence for the
comparison of npReFoam vs. npReWater generated from
comparisons, for example, of npReFoam vs. SC and npReWater
vs. SC). In this way, indirect evidence informs the
remaining 67 of the 91 network contrasts. The risk of bias
assessment was based on the most frequent level of bias
recorded for studies included in that comparison and denoted
using coloured lines (or links). A green link indicates no
serious study limitations; yellow indicates serious limitations;
and red indicates very serious limitations.

February 23, 2018 17 / 29
inconsistency in the network using either the design-by-
treatment interaction model or the
model of Lu and Ades [34]. There was one loop with potential
inconsistency (SC-npReFoam-
pActAir): this was likely due to the influence of one pairwise
meta-analysis in the loop which
had high heterogeneity (non-powered reactive foam surfaces
versus standard hospital
surfaces).
The common network heterogeneity was moderate: tau
2
= 0.195; and I
2
= 56% (95% CI: 36
to 70%). This means that there was moderate variation in the
mean effect size estimate across
studies in each network contrast (i.e. in one network contrast,
some included studies may sug-

gest benefit for one intervention group but others may suggest
harm). This moderate common
network heterogeneity may be due to the very high
heterogeneity (I
2
> 75%) of three pairwise
meta-analyses in the network (powered or non-powered reactive
low-air-loss air surfaces,
non-powered reactive sheepskin surfaces, and non-powered
reactive foam surfaces compared
with standard hospital surfaces). Additionally, subgroup
analysis suggested that funding
sources, considering operating theatres as settings or not,
follow-up duration, and baseline
skin status defined by authors may explain the network
heterogeneity (tau
2
from 0.195 to
0.160, 0.160, 0.178, and 0.129, respectively) but risk of bias
assessment and setting may not (see
S10 and S11 Files for the above analyses).
Fig 3. Results of pairwise meta-analyses via RevMan and
network meta-analysis with consistency model via STATA for
pressure ulcer incidence. Results of
pairwise meta-analyses with the numbers of included studies

and participants are presented above the diagonal cells (see S7
File); network meta-analysis results and the
corresponding certainty of evidence assessments are shown
below the diagonal cells. The diagonal cells show the codes of
intervention groups and their SUCRA values
and rankings in brackets: SC = standard hospital surfaces,
npReFibre = non-powered reactive fibre surfaces, npReFoam =
non-powered reactive foam surfaces,
npReGel = non-powered reactive gel surfaces, npReSheepskin =
non-powered reactive sheepskin surfaces, npReWater = non-
powered reactive water surfaces,
pActAir = powered active air-cells surfaces, pActAirnpReFoam
= powered active air-cells surfaces plus non-powered reactive
foam surfaces, pActLAL = powered active
low-air-loss air surfaces, pHybridAir = powered hybrid air-cells
surfaces, pHybridLAL = powered hybrid low-air-loss air
surfaces, pReAirfluid = powered reactive air-
fluidised surfaces, pnpReAir = powered or non-powered
reactive air-cells surfaces, and pnpReLAL = powered or non-
powered reactive low-air-loss air surfaces. ⊕⊕⊕◯
= Moderate certainty of evidence; ⊕⊕◯
◯= Low certainty of
evidence; and ⊕◯
◯
◯= Very low certainty of evidence.
February 23, 2018 18 / 29

Prevention network: Results of sensitivity analyses. Sensitivity
analyses did not suggest
that missing data and unpublished data would affect the relative
effects and rankings of inter-
ventions groups (see S8 File).
Prevention network: Publication bias. No funnel plot was
produced for the pairwise
meta-analyses because none included more than 10 studies. For
the network meta-analysis,
the comparison-adjusted funnel plot appeared slightly
asymmetric, suggesting the possible
presence of small-study effects; i.e. advanced support surfaces
like powered hybrid air surfaces
appear to have favourable prevention effects in small studies
(see S9 File).
Comfort network: Summary of included evidence. Twelve of 65
studies (18%) presented
outcome data on patient comfort, of which eight studies could
not be included in the network:
six studies were excluded as they compared support surfaces
from the same intervention

groups (Refs 11, 13, 20, 37, 41, 42 in the Table 2), and two
(Refs 39, 44 in the Table 2) could
not be connected to the network. Thus, the final network
included four studies (Refs 1, 17, 19,
57 in the Table 2) (with 802 participants) which formed six
direct comparisons and a network
of six intervention groups (Fig 4).
Comfort network: Main findings. The results of the pairwise and
network meta-analyses
are summarised in Fig 5 along with the GRADE-based
assessment of the certainty of the evi-
dence in the network meta-analysis. Four out of six (67%) direct
comparisons had no serious
limitations but another two had very serious limitations; and the
whole network had serious
Fig 4. Network plot for the patient comfort on a support surface
produced by STATA networkplot command. Six
intervention groups (i.e., six nodes) are coded in the plot: SC =
standard hospital surfaces, npReFoam = non-powered
reactive foam surfaces, npReWater = non-powered reactive
water surfaces, pActAir = powered active air-cells surfaces,
pReAirfluid = powered reactive air-fluidised surfaces, pnpReAir
= powered or non-powered reactive air-cells surfaces.
Taking any two of the six nodes forms 15 network contrasts.
The size of each node is proportional to the number of

direct comparisons involving each intervention group. The six
lines between nodes in the plot represent the only direct
comparisons and line thickness is proportional to the number of
studies involved in each direct comparison. The
direct evidence arising from two or more comparisons can
generate indirect evidence for contrasts that have not been
compared in head-to-head RCTs (e.g., indirect evidence for the
comparison of npReFoam vs. npReWater generated
from comparisons of npReFoam vs. SC and npReWater vs. SC).
In this way, indirect evidence informs nine of the 15
network contrasts. The risk of bias assessment was based on the
most frequent level of bias recorded for studies
included in that comparison and denoted using coloured lines
(or links). A green link indicates no serious study
limitation, yellow indicates serious limitations; and red very
serious limitations.
February 23, 2018 19 / 29

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