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.

1. Mechanical Ventilation
Graphics
Dr.s.vijay anand

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

3. Mechanical Ventilation
Graphics
SCALARS LOOPS

4. SCALARS
Flow/Time
Pressure/Time
Volume/Time

5. •Scalars: Plot pressure, volume, or flow against
time. Time is the x-axis.
•

6. Pressure-Volume Flow-Volume
LOOPS

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.

12.  Distinguishing breath type
 Trigger Sensitivity
 Plateau pressure
 Rate & I:E
 Peak Flow [VC]
 PS characteristics
 Lung mechanics

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]

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

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

28.  A – scooped out waveform b/c
inadequate flow for pt demand
 B – bulging indicates too much flow
•Adjusting Peak Flow [ VC]

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

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

41. 1 2 3 4 5 6
SEC
120
-120
V
.
LPM
Expiratory Flow Rate and Changes
in Expiratory Resistance

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

47.  Pressure-Volume Loops
 Flow-Volume Loops

48. 0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
VT

49. Mandatory Breath
Inspiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
VT

50. Mandatory Breath
Expiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
Inspiration
VT Counterclockwise

51. Spontaneous Breath
Inspiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
VT
Clockwise

52. Spontaneous Breath
Inspiration
Expiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
VT
Clockwise

53. Assisted Breath
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
Assisted Breath
VT

54. Assisted Breath
Inspiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
Assisted Breath
VT

55. Assisted Breath
Inspiration
Expiration
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH2O
Assisted Breath
VT Clockwise to
Counterclockwise

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)]

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

60. Triangle
ABE
Total WOB
Elastance &
Resistance

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

63.  Volume
remains
Constant
 Pressures
change

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

67.  •Air trapping
 •Airway Obstruction
 •Airway Resistance
 •Bronchodilator Response
 •Insp/Exp Flow
 •Flow Starvation
 •Leaks
 •Water or Secretion accumulation
 •Asynchrony

69. Volume
Tidal Volume
Inspiration
Expiration

70. Volume
Peak Expiratory Flow
Peak Inspiratory Flow
Tidal Volume
Inspiration
Expiration

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

74. Exp
volume
does not
return to
zero
Circuit or
pt leak

75. Exp flow does
not return to
zero
Pt still
exhaling
volume when
next breath
begins

76. 2
1
1
2
3
3
V
LPS
.
BEFORE
V
LPS
.

77. 2
1
1
2
3
3
V
LPS
.
BEFORE AFTER
Worse
2
1
1
2
3
3
V
LPS
.

78. 2
1
1
2
3
3
V
LPS
.
VT
INSP
EXH
BEFORE AFTER
Worse Better
2
1
1
2
3
3
V
LPS
.
2
1
1
2
3
3
V
LPS
.

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.

80.  Susan philbeam textbook of mechanical
ventilation