Objective--To gauge whether recording of ambulatory blood pressure during the night causes arousal f...

1. high blood pressure 19
Objective--To gauge whether recording of ambulatory blood pressure during the night causes
arousal from sleep and a change in the continuous blood pressure level recorded simultaneously.
Design--Repeated measurement of blood pressure level with two ambulatory blood pressure
machines (Oxford Medical ABP and AAndD TM2420) during continuous measurement of beat to
overcome blood pressure and continuous electroencephalography.
Setting--Sleep research laboratory.
Subjects--Six normal subjects.
Main outcome measures--The time period of electroencephalographic arousal along with high blood
pressure symptoms in men the beat to conquer modifications in blood pressure created by the
measurement of ambulatory blood pressure levels; the dimensions of any changes that this arousal
and alter in blood pressure created in the blood pressure level recorded through the ambulatory
machine.
Results--Both ambulatory hypertension machines caused arousal from sleep: the mean time of
arousal was 16 seconds (95% range -202) together with the 8 and ABP seconds (-73) together with
the TM2420. Both also caused a boost in beat to conquer hypertension. During non-rapid eye
movement sleep, this rise resulted in the ABP machine overestimating the genuine systolic blood
pressure level while asleep from a mean of 10 (SD 14.8) mm Hg as well as the TM2420 by way of a
mean of 6.3 (8.2) mm Hg. Measurements in individual subjects changed by approximately 23 mm
Hg, although on average, diastolic pressure was not changed. These changes varied in dimensions
among stages and subjects of sleep and were seen after measurements that failed to cause any
electroencephalographic arosual.
Conclusions--Ambulatory blood pressure levels machines cause appreciable arousal from sleep and
for that reason alter the blood pressure they are trying to record. This effect must be considered
when recordings of hypertension at nighttime are interpreted in clinical work and epidemiological

2. research.
Introduction
24 hour recordings of ambulatory blood pressure level are popular in treating and diagnosing
hypertension as well as in epidemiological studies. These profiles are better at predicting
cardiovascular morbidity and mortality than isolated measurements carried out in clinics[1] and
avoid the misleading rise in blood pressure level that high blood pressure symptoms in men may
occur when measurements are produced by medical staff.[2] O'Brien et al suggested that the
absence of the regular lowering of hypertension at night during ambulatory recordings may be an
impartial predictor of hypertensive end organ damage.[3] However, transient auditory and tactile
stimuli delivered during sleep and lasting just one or two seconds produce a transient surge in
hypertension even though cortical electroencephalographic arousal will not follow.[4] Previous work
has suggested that this rise could cause appreciable disturbances in blood pressure during
ambulatory measurement.[4] This research aimed to establish if this type of effect is likely to be
essential in recordings of ambulatory blood pressure levels at night.
methods and Subjects
We studied six normal adults (two women) aged 19 to 21 without any reputation of cardiovascular
disease or disease associated with sleep. The study was approved by Central Oxford Research Ethics
Committee.

3. RECORDING AMBULATORY Blood Pressure Level
We studied each subject twice, employing a different ambulatory blood pressure machine on each
occasion. The 2 machines used were the ABP (OxfordMedical and Abingdon, United Kingdom) as
well as the TM2420 (A&DLimited and Tokyo, Japan). Three subjects were randomised to one
machine first and three for the other, and also the two recordings
http://www.heart.org/HEARTORG/Conditions/HighBloodPressure/AboutHighBloodPressure/Understa
nding-Blood-Pressure-Readings_UCM_301764_Article.jsp for each subject were made at the very
least 14 days apart. Recordings were started at 0900, and measurement cycles (approximately 60
seconds) were initiated every 30 minutes throughout the following one day. While asleep the strain
from the arm cuff in the machine was monitored with a calibrated pressure line coupled to the
inflation tubing and was continuously stored together with the data on beat to overcome blood
pressures (see below).

4. SLEEP STAGES AND AROUSAL
The subjects slept inside a sleep laboratory and were continuously monitored with the infrared
audiovisual recording system. Overnight an electroencephalogram ([C.sub.2]/[A.sub.3]), eye
movements (two channels), plus a chin electromyogram were recorded; the subjects' sleep was
staged from the signals in accordance with standard criteria.[5]

5. We noted the duration of each arousal from sleep which
was as a result of inflation from the cuff measuring the
ambulatory blood pressure level. During non-rapid eye
movement sleep the duration was taken as being the
length of increased high frequency activity inside the
electroencephalogram, but during rapid eye movement
sleep it was actually taken because the time period of
increased activity in the electromyogram as high
frequency activity is spontaneously present in an
electroencephalogram in this stage of sleep. We staged
sleep and calculated the time period of arousals blind,
before analysing the hypertension recordings.
BEAT To Conquer BLOOD PRESSURE Throughout Sleep
Arterial beat to defeat diastolic and systolic blood pressures were recorded through the third finger
from the hand contralateral to this connected to the ambulatory blood pressure levels machhine with
an infrared plethysmographic volume clamp (Finapres, Ohmeda and Colorado United States Of
America).[6] The blood pressures were synchronised using the stages of sleep, as well as the
pressure in the ambulatory cuff was continuously stored using the beat to beat blood pressures.

6. Research into the modifications in the beat to conquer blood pressure levels during ambulatory
recording was restricted to those measurement cycles wherein the hand from which the beat to
defeat blood pressure level was being recorded did not move first minute once the cuff had begun to
inflate. This was confirmed from the audiovisual recording and the lack of movement artefacts from
the record of hypertension.
The average systolic and diastolic pressures throughout the last 10 seconds before inflation of the
cuff were utilised as the baseline with which subsequent changes were compared. The systolic and
diastolic changes through the baseline were calculated for all the next six periods of 10 seconds, and
also the peak blood pressure levels over these 60 seconds was noted.
The effects of the boost in hypertension during ambulatory measurement on the recorded systolic
and diastolic pressures were expressed because the change in beat to defeat blood pressure level
from the baseline to the stage in which the ambulatory machine identified the diastolic and systolic
pressures. Some time in which the ambulatory machine identified these pressures was come to be
when the pressure during the deflation in the arm cuff equalled the subsequently reported diastolic
and systolic pressures.