1. Ventilator Graphics Emeritus Professor Georgia State University
Vijay Deshpande, MS, RRT, FAARC
Emeritus Professor
Georgia State University
Atlanta, Georgia, USA
Adjunct Visiting Professor,
Manipal University
College of Allied Health Sciences
Manipal, Karnataka, INDIA

2. Mechanical Ventilation
SCALARS
LOOPS
Graphics

3. Inspiratory Flow Pattern
Peak inspiratory flow rate
PIFR
Beginning of expiration
exhalation valve opens
Inspiration
Insp. time TI
Expiratory Time TE
Flow (L/min)
Total cycle time
TCT
Time (sec)
Beginning of inspiration
exhalation valve closes
Expiration

4. Expiratory Flow Pattern
Beginning of expiration
exhalation valve opens
Inspiration
Expiratory time TE
Time (sec)
Flow (L/min)
Duration of
expiratory flow
Expiration
Peak Expiratory Flow Rate
PEFR

5. Auto-PEEP Time (sec) Flow (L/min) Inspiration Normal Patient}
Air Trapping
Auto-PEEP
Expiration

6. Inadequate Inspiratory Flow
Active Inspiration or Asynchrony
Patient’s effort
Normal
Abnormal
Time (sec)
Flow
(L/min)

7. Volume Ventilation breaths are Volume Cycled
Inspiratory Tidal Volume
Volume Cycling
Volume (ml)
Inspiration
Expiration TI
Time (sec)

8. Air Leak
Volume (ml)
Air Leak
Time (sec)

9. Components of Inflation Pressure
PIP }
Transairway Pressure (PTA)
Exhalation Valve Opens
Paw (cm H2O)
Pplateau
(Palveolar)
Inspiratory Pause
Expiration
Begin Inspiration
Time (sec)
Begin Expiration

10. Inadequate Inspiratory Flow
Inadequate Flow
Adequate Flow
(cm H2O)
Paw
Time (sec)

11. Assisted Mode (Volume-Targeted Ventilation)
Patient triggered, Flow limited, Volume cycled Ventilation
Flow
L/m
Pressure
cm H2O
Preset VT
Volume Cycling
Volume mL
Time (sec)
From: Essentials of Ventilator Graphics- An interactive CD. Vijay Deshpande, MS, RRT and Ruben Restrepo, MD, RRT. Available at

12. SIMV (Volume-Targeted Ventilation)
Flow
L/m
Pressure
cm H2O
Volume mL
Spontaneous Breaths

13. SIMV + PS (Pressure-Targeted Ventilation)
Time-Cycled
Flow-Cycled
Pressure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Set PC level
Set PS level
Time (sec)
Fig 7.21
PS Breath

14. PSV Flow L/m Pressure cm H2O Volume mL Time (sec) Set PS level
Flow Cycling
Set PS level
Pressure
cm H2O
Volume mL
Time (sec)

15. PSV Flow-Cycle Criteria
Peak Inspiratory Flow
Flow
40%
20% 5%
Simply put, the lower the ESENS, the longer the time before inspiration ends. The higher the ESENS setting, the shorter the inspiratory time. In general, the most appropriate ESENS setting is compatible with the patient’s condition, neither extending nor shortening the patient’s intrinsic inspiratory phase. ESENS can be adjusted by patient assessment. If inspiratory times appear to exceed the inspiratory efforts of the patient, a higher ESENS can be attempted to see if patient comfort improves. If the breath appears to be terminating prematurely, a lower ESENS can be set and patient comfort re-evaluated as well as it’s effect on tidal volume. T 36 36 36 36 36

16. CPAP + PSV ( BiPAP ) Flow Cycling Volume mL Flow L/m Pressure cm H2O
Set PS level
Pressure
cm H2O
CPAP level
Volume mL
Time (sec)
Fig 7.31

17. Components of Pressure-Volume LoopVT
Expiration
Volume (mL)
Inspiration
PIP
Paw (cm H2O)

18. Air Leak
Volume (ml)
Air Leak
Pressure (cm H2O)

19. Inadequate Inspiratory Flow
Volume
(ml)
Active Inspiration
Inappropriate Flow
Normal
Abnormal
Paw (cm H2O)

20. Increased Raw Higher PTA Normal Slope Lower Slope Pressure (cm H2O)
Vol (mL)
Normal Slope
Lower Slope
Pressure (cm H2O)

21. Lung Compliance Changes and the P-V Loop
Volume Targeted Ventilation
Preset VT
COMPLIANCE
Increased
Normal
Decreased
Volume (mL)
Paw (cm H2O)
PIP levels

22. Over-distention Preset Tidal Volume Volume (ml) Pressure (cm H2O)
With little or
no change in VT
Normal
Abnormal
Volume (ml)
Paw rises
Pressure (cm H2O)

23. Lung Compliance Changes and the P-V Loop
Volume Targeted Ventilation
Preset VT
COMPLIANCE
Increased
Normal
Decreased
Volume (mL)
Paw (cm H2O)
PIP levels

24. Flow-Volume Loop Inspiration PIFR FRC VT PEFR Expiration Flow (L/min)
Volume (ml)
FRC VT
Flow (L/min)
PEFR
Expiration

25. Air Leak Normal Abnormal Inspiration Expiration Volume (ml)
Flow
(L/min)
Volume (ml)
Air Leak in mL
Normal
Abnormal
Expiration

26. Air Trapping Normal Abnormal Inspiration Expiration Flow (L/min)
Does not return
to baseline
Volume (ml)
Normal
Abnormal
Expiration

27. Assisted Mode (Pressure-Targeted Ventilation)
Patient Triggered, Pressure Limited, Time Cycled Ventilation
Time-Cycled
Pressure
Flow
Volume
(L/min)
(cm H2O)
(ml)
Set PC level
Time (sec)

28. Scalars in Assisted Mode
FIGURE 1

29. Pressure Control Ventilation Flow – Time Scalar
TIME CYCLING TI
Time
Fig 8.16

30. PCV with long T I or Decreased Lung Compliance
Flow
No Flow
Period
Exhalation Valve
Opens
Time
Set TI
Inspiratory flow
Decreases to zero
Fig 8.17

31. Pressure Control Ventilation with inadequate TI
Flow
TIME CYCLING
Exhalation valve opens TI
Time
Fig 8.18

32. Pressure Control Ventilation - Effect of Changes in Lung Compliance on
Flow-time scalar
A : Decreased Compliance
B : Normal compliance
C : Increased Compliance
Flow
TIME CYCLING C A B TI
Fig 8.19

33. Thank You !

34. Apnea Alarm Patient becomes Apneic Disconnection in Sedated Patient
Oversedation in
Patients on Low
rate SIMV or PCV

35. “Ventilator inoperative” Alarm
Absent Electrical Source
(Unplugged)
Power Failure
“Ventilator inoperative” Alarm
Internal Battery
has very low charge

36. High Minute Volume or High Respiratory Frequency
Pain
Anxiety
High Minute Volume or High Respiratory Frequency
Hypoxemia

37. Low PEEP Alarm Active Inspiration Inappropriate Alarm setting
A leak in the circuit

38. Other Useful Alarms High Minute Volume
Check Sensitivity setting for trigger level
If using external nebulizer, reset the alarm until the treatment
is completed, and then reset it to the initial setting.
Check physiological causes of increased minute ventilation
Low FiO2
Check Gas Source pressures
Check Oxygen sensor for proper function (using oxygen analyzer)

39. Kinking or displacement of the tube
Decreased
Lung Compliance
Increased
Resistance
Secretions
Bronchospasm
Kinking or displacement of the tube
Pneumothorax
Pulmonary Edema,
Pleural Effusion
High Pressure Alarm
Asynchrony
(patient fighting)
Inadequate Flow
Auto PEEP,
Improper Sensitivity
Coughing

40. Low Pressure Alarm Leak In the System, Associated with Tracheal Tube
Cuff Leak, Chest tube
leakage
Associated with
low minute ventilation
or low tidal volume
Low Pressure Alarm
Patient
Disconnection
Proximal Pressure
Line Disconnected

41. Low Tidal volume or Low Minute Volume
IN VOLUME VENTILATION
IN PRESSURE VENTILATION
Leak In the System
Partial Disconnection
Increase in f or decrease
in Tidal Volume
( In Volume Ventilation)
Increased Resistance
and/or Decreased Lung
compliance
(Leak in the system does NOT
Trigger low volume alarm)

43. Double triggering
Volume-targeted ventilation. Notice the circled double volume breath and the pressure-time
Waveform to drop below baseline triggering another breath immediately following the first
breath. Hallmark of double triggering-peak pressure of the second breath rises as the second
breath is stacked on the first breath.
From Nilsestuen J, Hargett K. Using Ventilator Graphics to Identify Patient-Ventilator Asynchrony. Resp Care 2005;50(2):

44. Double triggering Causes
Commonly occurs with VC continuous mandatory ventilation
Also with PSV with high termination flow criterion
High respiratory drive
Insufficient respiratory support such as minute ventilation or tidal volume too low with a high respiratory rate.
Patient’s Itime (neural) is different (longer) than the ventilator set Itime
Small Vt and short inspiratory time

45. Missed triggers
Missed trigger with pressure control ventilation using the expiratory flow waveform.
The arrow points to the positive flow deflection that is the hallmark sign of a missed trigger.
From: Branson R, Blakeman T, Robinson B. Respiratory Care, 2013

46. Ineffective inspiratory efforts corrected by flow and expiratory time
COPD receiving assist-control ventilation with a constant Vt
of 0.55 L. Arrows indicate ineffective ventilation with flow rate
at 30 L/min in A.
Black arrows indicate ineffective inspiratory efforts.
Inspiratory flow rate was increased to 90 L/min which
decreased inspiratory time and prolonged expiratory time.
This reduced dynamic hyperinflation and the number of
ineffective ventilations was reduced.
Increasing flow rate can help reduce ineffective triggering
in COPD patients with dynamic hyperinflation.
During pressure control ventilation reducing inspiratory time
will prolong expiratory time to help reduce dynamic
hyperinflation.
From:Kondili E, Prinianakis G, Georgopoulos D. Patient-Ventilator interaction. Br J Anaesth 2003;91(1):

47. Inspiratory Rise Time

48. Inspiratory Time Inspiratory Time
Too Short May be able to deliver more tidal volume if inspiratory time lengthen to baseline
Normal: Good, Flow into lung has stopped, no extra pressure held in lung that is not wanted
Too Long: No Flow at end inspiration Pressure is held in lung, may cause increase lung injury