Ventilator Graphics

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1. BASIC PRINCIPLES OF MECHANICAL BASIC PRINCIPLES OF MECHANICAL
VENTILATION ANDVENTILATOR GRAPHICSVENTILATION ANDVENTILATOR GRAPHICS

2. BASIC PRINCIPLES OF MECHANICAL VENTILATIONBASIC PRINCIPLES OF MECHANICAL VENTILATION
Regardless of the disease states when a patient fails to
ventilate or oxygenate adequately the problem lies in 1
of 6 pathophysiological factors
2.Increased airway resistance
3.Change in lung compliance
4.Hypoventilation
5.V/Q mismatch
6.Intrapulmonary shunting
7.Diffusion defects

3. AIRWAY RESISTANCE
Normal airway resistance in term newborn is 20-40cm
H2O/l/sec
Normal airway resistance in adults is 0.6-cm of H2O /l/sec
Resistance increases by following
4.Inside the airway retained secretions
5.In the wall swelling or neoplasm
6.Outside the wall eg. tumor
Simplified Poiseuille’s Law P=V/ r4
P= driving force V=airflow , r=radius of airway

4. CONDITIONS LEADING TO AIRWAY RESISTANCE
Emphysema
Asthma
Bronchiectasis
Postintubation obstruction
Foreign body
Endotracheal tube (small size and long)
Condensation in vent circuit
ALTB
Bronchiolitis
Epiglottitis

5. AIRWAY RESISTANCE AND WORK OF BREATHING
Airway resistance ( Raw) is P/ V
 P=peak airway pressure-plateau pressure
V=flow
Increase in airway resistance means increase in work
of breathing (i.e. pressure change)
Hypoventilation may result if patient is unable to
overcome the resistance by increasing the work of
breathing
It leads to ventilatory and oxgenation failure

6. VENTILATORY FAILURE is failure of lungs to
eliminate CO2
OXGENATION FAILURE is failure of lung and heart
to provide adequate oxygen for metabolic needs

7. LUNG COMPLIANCE
Compliance is lung expansion (volume change) per unit pressure
change(work of breathing) V/ P
Abnormal high or low compliance impairs the patient ability to
maintain effective gas exchange
STATIC COMPLIANCE is measured when there is no airflow(using
plateau pressure –PEEP
STATIC COMPLIANCE = tidal volume /plateau pressure- PEEP
DYNAMIC COMPLIANCE is measured when airflow is present(using
the peak airway pressure- PEEP)
DYNAMIC COMPLIANCE = tidal volume / peak airway pressure- PEEP
Normal range of compliance in newborn is 1.5-2 ml/cmH2O/kg
Normal range of compliance in adults dynamic= 30-40 ml/cmH2O
Normal range of compliance in adults static= 40-60 ml/cmH2O

8. LUNG COMPLIANCE CONT-
Static compliance reflects the elastic properties
(elastic resistance) of lung and chest wall
Dynamic compliance reflects the airway
(nonelastic)resistance and the elastic properties
(elastic resistance) of lung and chest wall
Conditions causing change in static compliance
invoke similar changes in dynamic compliance
Where airway resistance is the only abnormality
dynamic compliance change independently

9. CLINICAL CONDITIONS THAT DECREASE THE
COMPLIANCE

TYPE OF COMPLIANC
2.STATIC
8.DYNAMIC
CONDITIONS
2.ATELECTASIS
3.ARDS
4.Pneumothorax
5.Obesity
6.Retained secretions
9.Bronchospasm
10.Kinking of ET tube
11.Airway obstruction

10. HIGH COMPLIANCE
Emphysema
Surfactant therapy

11. VENTILATORY FAILURE
5 mechanisms lead to ventilatory failure
2.Hypoventilation
3.Persistent ventilation perfusion mismatch
4.Persistent intrapulmonary shunting
5.Diffusion defect
6.Reduction in PIO2 i.e. inspired oxygen tension

12. HYPOVENTILATION
Caused by depression in CNS
Neuromuscular disease
Airway obstruction
In a clinical setting hypoventilation is characterised
by a reductionof alveolar ventilation and increase in
arterial CO2 tension

13. VENTIATION PERFUSION MISMATCH
Disease process which causes obstruction or atelectasis
result in less oxygen being available leading to low V/Q
Pulmonary embolism is an example that decreases
pulmonary perfusion and high V/Q
T/T in mechanical ventilation include increasing rate ,
tidal volume , FiO2
T/t directing towards removing obstruction,recruiting
atelectatic zones and preventing closure

14. INTRAPULMONARY SHUNTING
Causes refractory hypoxia
 normal shunt is less than 10%
10-20%mild shunt
20-30% significant shunt
>30% critical and severe shunt
eg pneumonia and ARDS
Classic Qs/Qt=( CcO2-CaO2)/(CcO2-CvO2)

15. DIFFUSION DEFECT
TYPE
2.Decrease in pressure
gradient
5.Thickening of A-C
membrane
7.Decrease surface
areaof A-C membrane
9.Insufficient time of
diffusion
CLINICAL CONDITIONS
2.High altitude, fire
combustion
5.Pulmonary edema and
retained secretions
7.Emphysema ,
pulmonary fibrosis
9.tachycardia

16. Purpose of GraphicsPurpose of Graphics
Graphics are waveforms that reflect the patient-
ventilator system and their interaction.
Purpose of monitoring graphics includes:
•Allows user to interpret, evaluate, and troubleshoot
the ventilator and the patient’s response to ventilator.
•Monitors the patient’s disease status (C and Raw).
•Assesses patient’s response to therapy.
•Monitors ventilator function
•Allows fine tuning of ventilator to decrease WOB,
optimize ventilation, and maximize patient comfort.

17. Types of WaveformsTypes of Waveforms
Scalars: plot pressure/volume/flow against time…
time is the x axis
Loops: plot pressure/volume/flow against each
other…there is no time component
Six basic waveforms:
•Square: AKA rectangular or constant wave
•Ascending Ramp: AKA accelerating ramp
•Descending Ramp: AKA decelerating ramp
•Sinusoidal: AKA sine wave
•Exponential rising
•Exponential decaying
•Generally, the ascending/descending ramps are considered the same as the exponential
ramps.

18. Types of Waveforms Types of Waveforms
Pressure waveforms
•Square (constant)
•Exponential rise
•Sinusoidal
Flow waveforms
•Descending ramp
•Square (constant)
•Exponential decay
•Sinusoidal
•Ascending ramp
Volume waveforms
•Ascending ramp
•Sinusoidal
•Sinusoidal waves are seen with spontaneous, unsupported breathing.

19. Types of Waveforms Types of Waveforms
Volume Modes Pressure Modes
Volume Control/ SIMV (Vol. Control) Pressure Control/ PRVC
SIMV (PRVC)
SIMV (Press. Control)
Pressure Support/
Volume Support
Pressure
Flow
Volume
Pressure
Flow
Volume

20. Pressure/Time ScalarPressure/Time Scalar
•In Volume modes,
the shape will be
an exponential
rise or an
accelerating ramp
for mandatory
breaths.
In Pressure modes, the
shape will be rectangular
or square.
This means that pressure
remains constant
throughout the breath
cycle.
•In Volume modes, adding an inspiratory pause may improve distribution of ventilation.

21. Pressure/Time ScalarPressure/Time Scalar
•Air trapping (auto-PEEP)
•Airway Obstruction
•Bronchodilator Response
•Respiratory Mechanics (C/Raw)
•Active Exhalation
•Breath Type (Pressure vs. Volume)
•PIP, Pplat
•CPAP, PEEP
•Asynchrony
•Triggering Effort
Can be used to assess:

22. Pressure/Time ScalarPressure/Time Scalar
•The baseline for the pressure waveform increases when PEEP is added.
•There will be a negative deflection just before the waveform with patient
triggered breaths.
5
15
No patient effort Patient effort
PEEP

+5

23. Pressure/Time ScalarPressure/Time Scalar

A
B
1
2
Inspiratory pause
= MAP
1 = Peak Inspiratory Pressure (PIP)
2 = Plateau Pressure (Pplat)
A = Airway Resistance (Raw)
B = Alveolar Distending Pressure
• The area under the entire curve represents the mean airway pressure (MAP).

24. Pressure/Time ScalarPressure/Time Scalar
Increased Airway Resistance Decreased Compliance
PIP
Pplat
PIP
Pplat
A. B.
•A-An increase in airway resistance causes the PIP to increase, but Pplat pressure
remains normal.
•B-A decrease in lung compliance causes the entire waveform to increase in size.
The difference between PIP and Pplat remain normal.

25. Volume/Time ScalarVolume/Time Scalar
The Volume waveform will generally have a “mountain
peak” appearance at the top. It may also have a plateau, or
“flattened” area at the peak of the waveform.
•There will also be a plateau if an inspiratory pause set or inspiratory hold maneuver is
applied to the breath.

26. Volume/Time ScalarVolume/Time Scalar
•Air trapping (auto-PEEP)
•Leaks
•Tidal Volume
•Active Exhalation
•Asynchrony
Can be used to assess:

27. Volume/Time ScalarVolume/Time Scalar
Inspiratory Tidal Volume
Exhaled volume returns
to baseline

28. Volume/Time ScalarVolume/Time Scalar
Air-Trapping or Leak
•If the exhalation side of the waveform doesn’t return to baseline, it could be
from air-trapping or there could be a leak (ETT, vent circuit, chest tube, etc.)
Loss of volume

29. Flow/Time ScalarFlow/Time Scalar
In Volume modes, the
shape of the waveform will
be square or rectangular.
This means that flow
remains constant
throughout the breath
cycle.

In Pressure modes,
(PC, PS, PRVC,
VS) the shape of
the waveform will
have a
decelerating ramp
flow pattern.

30. Flow/Time ScalarFlow/Time Scalar
•Air trapping (auto-PEEP)
•Airway Obstruction
•Bronchodilator Response
•Active Exhalation
•Breath Type (Pressure vs. Volume)
•Flow Waveform Shape
•Inspiratory Flow
•Asynchrony
•Triggering Effort
Can be used to assess:

31. Flow/Time ScalarFlow/Time Scalar
Volume
Pressure

32. Flow/Time ScalarFlow/Time Scalar
•The decelerating flow pattern may be preferred over the constant flow pattern. The same
tidal volume is delivered, but with a lower peak pressure.

33. Flow/Time ScalarFlow/Time Scalar
Auto-Peep (air trapping)
•If expiratory flow doesn’t return to baseline before the next breath starts, there’s auto-
PEEP (air trapping) present , e.g. emphysema.
Start of next breath
Expiratory flow
doesn’t return to
baseline
= Normal

34. Flow/Time ScalarFlow/Time Scalar
Bronchodilator Response
•To assess response to bronchodilator therapy, you should see an increase in peak
expiratory flow rate.
•The expiratory curve should return to baseline sooner.
Peak Exp. Flow
Improved Peak Exp. Flow
Shorter
E-time
Longer
E-time
Pre-Bronchodilator Post-Bronchodilator

35. Types of Waveforms Types of Waveforms
Volume Modes Pressure Modes
•In Pressure Limited, Time-cycled (control) modes, inspiratory flow should return to baseline.
•In Flow-cycled (support) modes , flow does not return to baseline.
Volume Control/ SIMV (Vol. control) Pressure Control/ PRVC
SIMV (PRVC)
SIMV (Press. control)
Pressure Support/
Volume Support
Pressure
Flow
Volume
Pressure
Flow
Volume

36. •Notice the area of no flow indicated by the red line. This is known as a “zero-flow state”.
•This indicates that I-time is too long for this patient.
Types of Waveforms Types of Waveforms

37. 15 305
250
500
Pressure/Volume LoopsPressure/Volume Loops

38. Pressure/Volume LoopsPressure/Volume Loops
Volume is plotted on the y-axis, Pressure on the x-
axis.
Inspiratory curve is upward, Expiratory curve is
downward.
Spontaneous breaths go clockwise and positive
pressure breaths go counterclockwise.
The bottom of the loop will be at the set PEEP level.
It will be at 0 if there’s no PEEP set.
If an imaginary line is drawn down the middle of
the loop, the area to the right represents inspiratory
resistance and the area to the left represents
expiratory resistance.

39. Pressure/Volume LoopsPressure/Volume Loops
•Lung Overdistention
•Airway Obstruction
•Bronchodilator Response
•Respiratory Mechanics (C/Raw)
•WOB
•Flow Starvation
•Leaks
•Triggering Effort
Can be used to assess:

40. inspiration
expiration
15 305
Dynamic
Compliance
A
A = Inspiratory
Resistance/
Resistive WOB
B
Pressure/Volume LoopsPressure/Volume Loops
(Cdyn)
•The top part of the P/V loop represents Dynamic compliance (Cdyn).
• Cdyn = Δvolume/Δpressure
500
250
B = Exp.
Resistance/
Elastic WOB

41. Pressure/Volume LoopsPressure/Volume Loops
15 305
Overdistention
“beaking”
•Pressure continues to rise with little or no change in volume, creating a “bird beak”.
•Fix by reducing amount of tidal volume delivered
500
250

42. Pressure/Volume LoopsPressure/Volume Loops
15 305
Airway Resistance
•As airway resistance increases, the loop will become wider.
•An increase in expiratory resistance is more commonly seen. Increased inspiratory
resistance is usually from a kinked ETT or patient biting.
“ hysteresis”
exp. resistance
insp. resistance
500
250

43. 15 305
250
500
15 305
Pressure/Volume LoopsPressure/Volume Loops
Increased Compliance Decreased Compliance
Example: Emphysema,
Surfactant Therapy
Example: ARDS, CHF,
Atelectasis
500
250

44. 15 305
Pressure/Volume LoopsPressure/Volume Loops
A Leak
•The expiratory portion of the loop doesn’t return to baseline. This indicates a leak.
500
250

45. 15 305
Pressure/Volume LoopsPressure/Volume Loops
Lower
Inflection Point
•The lower inflection point represents the point of alveolar opening (recruitment).
•Some lung protection strategies for treating ARDS, suggest setting PEEP just above the
lower inflection point.
Inflection Points
250
500

46. Point of upper inflection (Ipu)
C lt changed later during
Vt because of
overinflation of the alveoli
The reduction in Clt late
in inspiratory cycle is
called Ipu
The appearance of upper
shape PAO curve indicating
the presence of Ipu is
known as duck bill PVC

47. Flow/Volume LoopsFlow/Volume Loops
0
200 400 600
20
40
60
-20
-40
-60

48. Flow/Volume LoopsFlow/Volume Loops
Flow is plotted on the y axis and volume on the x axis
Flow volume loops used for ventilator graphics are the
same as ones used for Pulmonary Function Testing,
(usually upside down).
Inspiration is above the horizontal line and expiration is
below.
The shape of the inspiratory curve will match what’s set on
the ventilator.
The shape of the exp flow curve represents passive
exhalation…it’s long and more drawn out in patients with
less recoil.
Can be used to determine the PIF, PEF, and Vt
Looks circular with spontaneous breaths

49. Flow/Volume LoopsFlow/Volume Loops
•Air trapping
•Airway Obstruction
•Airway Resistance
•Bronchodilator Response
•Insp/Exp Flow
•Flow Starvation
•Leaks
•Water or Secretion accumulation
•Asynchrony
Can be used to assess:

50. Flow/Volume LoopsFlow/Volume Loops
0
200 400 600
20
40
60
-20
-40
-60
PEF
Start of
Inspiration
Start of
Expiration

51. 0
0
Flow/Volume LoopsFlow/Volume Loops
•The shape of the inspiratory curve will match the flow setting on the ventilator.

52. DIFFERENT FLOW VOLUME LOOPS
A, normal loop
B ski-slop observerved in exp. Flow
limitation
C Extrathoracic airway obstruction
with inspiratory and expiratory air
flow limitation seen in subglotic
stenosis and narrow endotracheal
tube
D Intrathoracic inspiratory airflow
limitationas seen with babies with
intraluminal obstruction
E unstable airway eg
tracheomalacia
F Erratic airflow in secretions

53. Flow/Volume LoopsFlow/Volume Loops
0
200 400 600
20
40
60
-20
-40
-60
Expiratory
portion of loop
does not
return to starting
point, indicating
a leak.
A Leak
•If there is a leak, the loop will not meet at the starting point where inhalation starts and
exhalation ends. It can also occur with air-trapping.
= Normal

54. 0
0
Reduced
PEF“scooping”
Flow/Volume LoopsFlow/Volume Loops
•The F-V loop appears “upside down” on most ventilators.
•The expiratory curve “scoops” with diseases with small airway obstruction (high
expiratory resistance). e.g. asthma, emphysema.
Airway Obstruction

55. Air Trapping (auto-PEEP)Air Trapping (auto-PEEP)
Causes:
•Insufficient expiratory time
•Early collapse of unstable alveoli/airways during exhalation
How to Identify it on the graphics
•Pressure wave: while performing an expiratory hold, the waveform rises
above baseline.
•Flow wave: the expiratory flow doesn’t return to baseline before the next
breath begins.
•Volume wave: the expiratory portion doesn’t return to baseline.
•Flow/Volume Loop: the loop doesn’t meet at the baseline
•Pressure/Volume Loop: the loop doesn’t meet at the baseline

56. Airway Resistance ChangesAirway Resistance Changes
Causes:
•Bronchospasm
•ETT problems (too small, kinked, obstructed, patient biting)
•High flow rate
•Secretion build-up
•Damp or blocked expiratory valve/filter
•Water in the HME
How to Identify it on the graphics
•Pressure wave: PIP increases, but the plateau stays the same
•Flow wave: it takes longer for the exp side to reach baseline/exp flow rate
is reduced
•Volume wave: it takes longer for the exp curve to reach the baseline
•Pressure/Volume loop: the loop will be wider. Increase Insp. Resistance
will cause it to bulge to the right. Exp resistance, bulges to the left.
•Flow/Volume loop: decreased exp flow with a scoop in the exp curve
How to fix
•Give a treatment, suction patient, drain water, change HME, change ETT,
add a bite block, reduce PF rate, change exp filter.

57. Compliance ChangesCompliance Changes
Decreased compliance
•Causes
ARDS
Atelectasis
Abdominal distension
CHF
Consolidation
Fibrosis
Hyperinflation
Pneumothorax
Pleural effusion
How to Identify it on the graphics
Pressure wave: PIP and plateau
both increase
Pressure/Volume loop: lays
more horizontal
•Increased compliance
•Causes
Emphysema
Surfactant Therapy
• How to Identify it on the
graphics
Pressure wave: PIP and plateau
both decrease
Pressure/Volume loop: Stands
more vertical (upright)

58. Leaks Leaks
Causes
•Expiratory leak: ETT cuff leak , chest tube leak, BP fistula, NG tube
in trachea
•Inspiratory leak: loose connections, ventilator malfunction, faulty
flow sensor
How to ID it
•Pressure wave: Decreased PIP
•Volume wave: Expiratory side of wave doesn’t return to baseline
•Flow wave: PEF decreased
•Pressure/Volume loop: exp side doesn’t return to the baseline
•Flow/Volume loop: exp side doesn’t return to baseline
How to fix it
•Check possible causes listed above
•Do a leak test and make sure all connections are tight

59. AsynchronyAsynchrony
Causes (Flow, Rate, or Triggering)
•Air hunger (flow starvation)
•Neurological Injury
•Improperly set sensitivity
How to ID it
•Pressure wave: patient tries to inhale/exhale in the middle of the waveform, causing
a dip in the pressure
•Flow wave: patient tries to inhale/exhale in the middle of the waveform, causing
erratic flows/dips in the waveform
•Pressure/Volume loop: patient makes effort to breath causing dips in loop either
Insp/Exp.
•Flow/Volume loop: patient makes effort to breath causing dips in loop either
Insp/Exp.
How to fix it:
•Try increasing the flow rate, decreasing the I-time, or increasing the set rate to
“capture” the patient.
•Change the mode - sometimes changing from partial to full support will solve the
problem
•If neurological, may need paralytic or sedative
•Adjust sensitivity

60. AsynchronyAsynchrony
Flow Starvation
•The inspiratory portion of the pressure wave shows a scooping or “dip”, due to
inadequate flow.

61. AsynchronyAsynchrony
F/V Loop P/V Loop

62. Rise Time Rise Time &&
Inspiratory Cycle Off %Inspiratory Cycle Off %

63. Rise TimeRise Time
•The inspiratory rise time determines the amount of
time it takes to reach the desired airway pressure or
peak flow rate.
•Used to assess if ventilator is meeting patient’s demand in Pressure Support mode.
•In SIMV, rise time becomes a % of the breath cycle.

64. Rise TimeRise Time
If rise time is too fast, you can get an overshoot in the pressure wave,
creating a pressure “spike”. If this occurs, you need to increase the rise
time. This makes the flow valve open a bit more slowly.
If rise time is too slow, the pressure wave becomes rounded or
slanted, when it should be more square. This will decrease Vt delivery
and may not meet the patient’s inspiratory demands. If this occurs,
you will need to decrease the rise time to open the valve faster.
too slowtoo fast
pressure spike

65. Inspiratory Cycle OffInspiratory Cycle Off
•The inspiratory cycle off determines when the
ventilator flow cycles from inspiration to expiration, in
Pressure Support mode.
•The flow-cycling variable is given different names depending on the type of ventilator.
Also know as–
•Inspiratory flow termination,
•Expiratory flow sensitivity,
•Inspiratory flow cycle %,
•E-cycle etc…

66. Inspiratory Cycle OffInspiratory Cycle Off
•The breath ends when the ventilator detects inspiratory flow has dropped to a specific
flow value.
Inspiration ends
pressure
flow

67. Inspiratory Cycle OffInspiratory Cycle Off
•In the above example, the machine is set to cycle inspiration off at 30% of the patient’s
peak inspiratory flow.
100% of Patient’s
Peak Inspiratory Flow
Flow
100%
50%
30%
75%

68. Inspiratory Cycle OffInspiratory Cycle Off
•A –The cycle off percentage is too high, cycling off too soon. This makes the breath too
small. (not enough Vt.)
60%
10%
•B – The cycle off percentage is too low, making the breath too long. This forces the
patient to actively exhale (increase WOB), creating an exhalation “spike”.
Exhalation
spike
A B
100% 100%

69. Sources:Sources:
•Rapid Interpretation of Ventilator Waveforms Ventilator
Waveform Analysis –
Susan Pearson
•Golden Moments in Mechanical Ventilation – Maquet, inc.
•Servo-I Graphics – Maquet, inc.
•text book of physiology- Ganong
•David W Chang –clinical application of mechanical
ventilation
•Pulmonary function and graphics -Goldsmith

70. Thank You!Thank You!