Mechanical ventilation graphics provide important information to interpret patient response, disease status, and ventilator function. Scalars plot pressure, volume, or flow over time, while loops plot pressure versus volume or flow versus volume with no time component. Common waveforms include square, ramp, and sine waves. Pressure modes result in square pressure waves while volume modes produce ramp waves. Loops can indicate breath type and assess issues like air trapping, resistance, compliance, and asynchrony. Graphical analysis is a critical tool for ventilator management and optimization.
2. Allow users to interpret, evaluate, and
troubleshoot the ventilator and the patient’s
response to the ventilator.
Monitor the patient’s disease status (C and
Raw).
Assess the patient’s response to therapy.
Monitor proper ventilator function
Allow fine tuning of ventilator to decrease
WOB, optimize ventilation, and maximize
patient comfort
7. Loops: Plot pressure or flow against volume.
(P/V or F/V). There is no time component
8. •Generally, the ramp waves are considered the same
as exponential shapes, so you really only need to
remember three: square, ramp, and sinewaves.
9. Square wave:
Represents a constant or set parameter.
For example, pressure setting in PC mode or flowrate
setting in VC mode.
Ramp wave:
Represents a variable parameter
Will vary with changes in lung
characteristics
Can be accelerating or decelerating
Sine wave:
Seen with spontaneous, unsupported
breathing
10. In Volume modes, the shape of the pressure wave
will be a ramp for mandatory breaths
•In Volume modes, adding an inspiratory pause (or
hold) will add a small plateau to the waveform.
•This is thought to improve distribution of
ventilation
11. In Pressure modes, the shape of the pressure wave
will be a square shape.
•This means that pressure is constant during
inspiration or pressure is a set parameter.
13. Y axis – Pressure
X axis – Time
A-B = Inspiration
B – C = Expiration
MAP = Area under curve
PIP = Max insp Pressure
PEEP = baseline Pressure
14. Press wave is square [constant]
P wave is not affected by lung mechanics or pt flow
demand
Flow rate is according to lung mechanics, set P, & Insp
effort by pt
Flow wave rises rapidly to meet set P, then decreases
to a point necessary to maintain set P. [ expo decay or
continuously variable decelerating pattern]
Note the P & V plateaus in regard to the Flow which
ends before Ti is over
This condition provides the greatest volume
possible for that set P
Indicates the lung has met equilibrium [Plateau]
15.
16. This condix has a much shorter Ti [not allowing for
Plateau] but for a longer Te
Delivered volume is slightly decreased
17. A-B Inspiration
B-C Expiration
D shows second breath beginning before 1st breath has
exhaled fully
Indicates needing to decrease rate, increase Te, or
decrease Ti
•Adequate Rate, I:E
18.
19.
20.
21.
22. •Breath type
Mechanical breath [volume]
•Note at point A – there is no negative deflex
•Consistent Ti & Volume delivery
•Pressure continues to rise until set V is
reached, then breath cycles
23. •Breath type
•Mechanical Breath [ Pressure]
Consistent Ti & Pressure delivery
•P reaches limit early in I and holds
for Ti
•No Trigger
24. •Breath type
•Triggered Mechanical Volume Breath
•Note at point A – there is a negative
deflection, indicating the pt initiated a
triggered breath
25. Identified by negative inflex triggering breath
varying Inspiratory times
Note the different times of the above curves
VC-SIMV w/ PS
•Breath type
•Pressure Support breaths
26. A – represents Inspirax of a spontaneous Breath
B – represents Expirax of a Spontaneous breath
Spontaneous Mode – Every breath is pt triggered
& spontaneous in nature
•Breath type
•Spontaneous breath
27.
28. A – scooped out waveform b/c
inadequate flow for pt demand
B – bulging indicates too much flow
•Adjusting Peak Flow [ VC]
29.
30.
31.
32.
33. Note the
Exp Volume
is not = insp
Vol
Indicating
a leak
Flow &
Press both
return to
zero
•Air Trapping v. Air Leaks
34. Note the Exp
Volume > Insp
Volume
Indicating active
Ex due to air
trapping
Note the flow &
Press never return
to zero
•Active Exhalation
35.
36.
37. Y axis = flow
X axis = Time
A-B = inspiration
Above x axis
B-C = Expirax
Below X axis
D- Peak Inspiratory
Flow
E = Peak Expiratory
Flow [ PEFR]
38. B-D = Ti
B-C = INSP FLOW
C-D = INSP PAUSE
D-F = Te
D-E = EXP FLOW
E-F = EXP FLOW has
ended
Rate could be
increased until insp
begins at point E on
this pt without air
trapping
39.
40.
41. 1 2 3 4 5 6
SEC
120
-120
V
.
LPM
Expiratory Flow Rate and Changes
in Expiratory Resistance
42.
43. Exp flow is low &
slow, taking a long
time to rid the lungs of
volume.
Te is barely adequate
to allow for lung
emptying before next
breath
This pt may have
COPD or severe
asthma
Bronchodilator response
may be helpful to
evaluate
44. A – Insp flow does return to zero
Adequate Ti
B – Insp flow does NOT return to zero
Inadequate Ti
Allows for increasing Ti
this will increase Vt without increasing Pressure
45. Pressure remains
constant at level set
Flow increases as
pt demand
increases in order
to maintain the set
Pressure level
Volume increases
56. Dashed line plotted
based on the Static
Compliance calculation
drawn from zero to
peak PA
Peak PA – Pstatic or
Pplat
Note that the point
at which Peak PA is
also the point
where the volume
plateaus
PTA = xairway
pressure
[difference b/w the
airway
opening(Pawo) and
the Alveoli (PA)]
57.
58. Triangle APAE
Represents the amount of
mechanical work to
overcome the compliance
[elastic forces] of the chest
Area ACBPA represents
amount of work to
overcome Raw during
Insp
Triangle APAD represents
amount of work to
overcome Raw during
Exp
The insp area [area w/in
the hysteresis] represents
total WOB due to Raw
59. PTA = xairway pressure
[difference b/w the
airway
opening(Pawo) and
the Alveoli (PA)]
Represents the
amount of pressure
needed to overcome
resistance of the
lung
If Raw increases
this distance will
increase
If flow [turbulence]
increases, so does
this distance
61. Slope = line drawn
from zero through the
Pplat
As slope increases [
Pplat decreases]
compliance increases
for a set volume
As slope decreases [
Pplat increase]
compliance decreases
for a set volume
62. Decreased
compliance dz’s
Fibrosis, ARDS, pna,
Pulm edema,
Atelectasis, etc.
Short Time constant
states(fast lung units)
Increased compliance
dz’s
Emphysema,
uncomplicated COPD,
etc.
Long Time constant
states(slow lung units)
Pressure remains
constant while volumes
differ
64. Overdistension
B
A
0 20 40 60-20-40-60
0.2
0.4
0.6
LITERS
Paw
cmH2O
C
A = inspiratory pressure
B = upper inflection point
C = lower inflection point
VT
65. X axis – Volume
Y axis – Flow
Insp – above x axis
Exp – below x axis
Opposite of a
PFT tracing
Peak Exp Flow
Rate
Peak insp flow
66. •The shape of the inspiratory
portion of the curve will match the
flow waveform.
•The shape of the exp flow curve
represents passive exhalation.
•Can be used to determine the PIF,
PEF, and Vt
•Looks circular with spontaneous
breaths
71. A – normal Raw & exp
flow
B – increased Raw &
reduced exp flow
C – markedly
increased Raw &
reduced exp flow
Insp flow is unaffected
by Raw b/c the vent is
delivering a constant
flow [square
waveform]
72. Inner loop – increased
airway resistance
Outer Loop – after BD
therapy
Spike an artifact that
reflects the release of gas
trapped in the patient
circuit during
inspiration
compressible volume
release
It should not be valued as
PEFR
73. Note the severe
scooping of the exp
waveform
79. Waveforms and loops are graphical representation
of the data generated by the ventilator.
Typical Tracings
Pressure-time,
Flow-time,
Volume -time
Loops
Pressure-Volume
Flow-Volume
Assessment of pressure, flow and volume
waveforms is a critical tool in the
management of the mechanically
ventilated patient.