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1. Mechanical
Ventilation
Workshop
J. Christopher Farmer

2. “Play by the Rules”

3. Basic Principles:
Establish Harm-Free Goals
1. SaO2 85-90% with certain exceptions
2. Follow pH not PaCO2
3. VT: ARDS versus other lung conditions
4. Paw: ARDS versus other lung conditions
5. Avoid drugs that may prolong weaning
(sedatives, neuromuscular blockers)
Better is the enemy of good…

4. Basic Principles:
Establish Synchronization
PATIENT
DEMAND
VENTILATOR
DELIVERY
• FLOW
• PRESSURE
• VOLUME

5. Basic Principles:
Avoid Lung Injury
• PRESSURE
• VOLUME
COLLAPSE  RECRUITMENT
ALVEOLAR
SHEAR

6. Basic Principles:
The Target Zone

7. Basic Principles:
Lung immobilization = healing

8. patient
Diaphragm
}Pres
PAlv
P
Pleura
ventilator
P
Airway
Airway pressure
Flow
Time
Ti Te
Stroetz et al.
Basic Principles:
Coordination of Purpose

9. Basic Principles:
Know the Modes
CPAP

10. Basic Principles:
Know the Modes
SIMV

11. Basic Principles:
Know the Modes
SIMV + PRESSURE SUPPORT SIMV

12. Basic Principles:
Know the Modes
ASSIST CONTROL (CMV)

13. Basic Principles:
Know the Modes
CMV versus PC

14. Basic Principles:
Know the Modes
APRV
I E

15. Basic Principles:
Know the Waveforms

16. Basic Principles:
Know the Waveforms
What is the flow pattern?

17. Basic Principles:
Know the Waveforms
Is this a pressure supported or SIMV or VAC breath?

18. Basic Principles:
Know the Waveforms
Is this pressure support or pressure control?

19. Basic Principles:
Know the Waveforms
X
INADEQUATE
INSP. FLOW
Is the patient/ventilator synchronizing with the patient/ventilator?

20. Basic Principles:
Know the Waveforms
Inspiratory effort: patient work with pressure versus flow triggering
VENTILATOR
PATIENT
VENTILATOR TUBING CIRCUIT LENGTH

21. “Diagnosing the problem”

22. Disorders of flow
 Flow starvation
 Excess flow
 Outflow obstruction
 Inflow obstruction

23. Flow Starvation

24. CMV, Volume Cycled
Inspiratory Flow Starvation
 High respiratory drive
 Pain
 Fever
 Anxiety
 High inspiratory flow
demand
 Patient outstripping
the pre-set (fixed)
ventilator flow rate
 Scalping of pressure
waveform

25. Adjust Peak Flow to Meet
Patient Inspiratory Demand

26. Excess flow
INSPIRATORY FLOW
RATE = 50 L/min
LAMINAR
INSPIRATORY FLOW
RATE = 80 L/min
TURBULENT

27. Excess Flow
 Inspiratory flow rate exceeds patient
demand (flow rate)
 Rapid rise pressure tracing with
“pressure overshoot”
 More is not better!

28. Air TrappingAir Trapping
InspirationInspiration
ExpirationExpiration
NormalNormal
PatientPatient
Time (sec)Time (sec)
Air TrappingAir Trapping
AutoAuto--PEEPPEEP
}}
FlowFlow
(L/min)(L/min)
Outflow obstruction

29. A Auto - PEEP
10 cm H2O
External PEEP
0 cm H2O
B Auto - PEEP
10 cm H2O
External PEEP
8 cm H2O
C Net PEEP
12 cm H2O
External PEEP
12 cm H2O
Tobin MJ. Chest 1989; 96:449-451
Trigger Sensitivity and Auto-
PEEP

30. Minimizing the Impact of
Outflow Obstruction
1. Decrease rate (frequency)
2. Decrease VT
3. Increase inspiratory flow
rate
Volume vs Time ScalarVolume vs Time Scalar
InspirationInspiration
ExpirationExpiration
Time (sec)Time (sec)
VolumeVolume
(ml)(ml)
Inspiratory Tidal VolumeInspiratory Tidal Volume
TTII

31. Inflow Obstruction
RESISTANCE

32. Increased Paw:
Resistance versus Compliance
Components of Inflation
Pressure
Components of Inflation
Pressure
Begin InspirationBegin Inspiration Begin ExpirationBegin Expiration
11
22
BBAA
1. PIP1. PIP
2.2. PPplatplat/Alveolar Pressure/Alveolar Pressure
A. Airway ResistanceA. Airway Resistance
B. Distending PressureB. Distending Pressure
Time (sec)Time (sec)
PPawaw
(cm H(cm H22O)O)

33. Identifying the Cause of
Inflow Obstruction
“Kink” in the ET tube
Secretions or mucous plugging
Bronchospasm

34. Disorders of Pressure
Reduced lung compliance
Excess tidal volume (VT)

35. Reduced Lung Compliance
 Mainstem intubation
 Pneumothorax
 Pulmonary edema
(alveolar flooding)

36. Peak versus Plateau
Pressure

37. Excess VT:
Paw Overdistension and Barotrauma

38. Inappropriate I-Time
(Dyssynchrony)

39. Patient Perceives
“Insufficient” VT
“DOUBLE TRIGGERING”
MACHINE TI
PATIENT TI
T0
2ndbreathtriggered

40. Conclusions
1. Know the waveforms!
2. Synchronize the machine to the patient
3. “Seek” the cause of the problem by
analysis techniques shown here today
4. Use sedation only after you have
accomplished 1-3 (or in ARDS patients
with  VT