Mode of ventilation

Modes of Mechanical Ventilataion

1. Respiratory
Failure
VVs.s.
RespiratoryRespiratory
InsufficiencyInsufficiency
Associated withAssociated with
•Abnormal ABGs
•Immediate action is required
•Clinical signs may not be
very obvious
Associated withAssociated with
•Normal or near normal
ABGs
•Increased work of breathing
•Accompanied by dyspnea,
paradoxical breathing, use of
accessory muscles

2. Initiation of Mechanical Ventilation
Volume Ventilation Pressure Ventilation

3. Volume Ventilation

4. VOLUME TARGETED VENTILATION
Delivered Tidal Volume is ConstantDelivered Tidal Volume is Constant
Better Control on PaCOBetter Control on PaCO
22

5. Mode Selection
● Control Mode
● Assist Mode
● PEEP
● CPAP

6. PEEP and CPAP
● PEEP (Positive End Expiratory Pressure)
-
Mechanical CPAP
● CPAP (Continuous Positive Airway
Pressure) – Spontaneous PEEP

7. Controlled Mode
(Volume- Targeted Ventilation)
Preset V
T
Volume
Cycling
Dependent on
C
L
& Raw
Time (sec)
Flow
L/m
Pressure
cm H
2
O
Volume
mL
Preset Peak Flow
Time triggered, Flow limited, Volume cycled Ventilation

8. Assisted Mode
(Volume-Targeted Ventilation)
Time (sec)
Flow
L/m
Pressure
cm H
2
O
Volume
mL
Preset VT
Volume
Cycling
Patient triggered, Flow limited, Volume cycled Ventilation
From: Essentials of Ventilator Graphics- An interactive CD. Vijay Deshpande, MS, RRT and Ruben Restrepo, MD, RRT. Available at
www.respiratorybooks.com

9. Setting Trigger Sensitivity
Pressure
Inappropriate sensitivity setting

10. Pressure triggering imposes work on
the respiratory system that in some
cases is excessive. Triggering work of
breathing needs to be decreased.
ADVANCEMENT: Introduction of Flow Triggering

11. Flow Triggering

12. Flow Triggering
Flow Sensor Flow Sensor

13. On initiating a breath the patient
receives all mechanical breaths of set
tidal volume causing respiratory
alkalosis.
ADVANCEMENT: IMV and SIMV

14. SIMV
(Volume-Targeted Ventilation)
Spontaneous Breaths
Flow
L/m
Pressure
cm H
2
O
Volume
mL

15. Patients are experiencing increased work
of breathing during spontaneous breaths
through the tracheal tube in SIMV.
ADVANCEMENT: Pressure Support Ventilation

16. SIMVSIMV
(Volume-Targeted Ventilation)(Volume-Targeted Ventilation)
Spontaneous Breaths
Flow
L/m
Pressure
cm H
2
O
Volume
mL

17. Unsupported Breathing through a Tracheal Tube

18. Pressure drop shows imposed Pressure drop shows imposed
work across ET-Tube when work across ET-Tube when
flow is presentflow is present
What The What The CarinaCarina Sees Sees
Circuit Pressure
Lower Carina Pressure
Paw

19. Pressure
Flow
Volume
(L/min)
(cm H
2
O)
(ml)
SIMV + PS
(Pressure-Targeted Ventilation)
PS Breath
Set PS level
Set PC levelSet PC level
Time (sec)Time (sec)
Time-CycledTime-Cycled
Flow-Cycled

20. How much Pressure Support?

21. Components of
Inflation Pressure
Begin Expiration
P
a
w


(
c
m

H
2
O
)
Time (sec)
Begin Inspiration
PIPPIP
P
plateau
(Palveolar)
Transairway Pressure (P
TA
)}}
Exhalation Valve Opens
ExpirationExpiration
Inspiratory Pause

22. Initial Pressure Support LevelInitial Pressure Support Level
PSV level =PIP - PPlateau

23. Pressure Support Ventilation
( PSV )
Strictly an assist form of mechanical ventilation
Augments spontaneous tidal volume with a preselected
level of positive inspiratory pressure
Overcomes imposed work of breathing due to :
Artificial Airways
Demand valve system
Ventilator circuitry
Classified as a Pressure-limited, flow-cycled, assisted
ventilation

24. PSV
Time (sec)
Flow Cycling
Set PS
level
Flow
L/m
Pressure
cm H
2
O
Volume
mL

25. Acute Lung Injury (ALI), Acute
Respiratory Distress Syndrome (ARDS)
and Volume Ventilation

26. Dilemma in Ventilatory Management of ARDS
Objective: Reopen collapsed and recruitable alveoli
Strategy: Application of Positive Pressure Ventilation
Commonly used Mode of Ventilation: Volume Targeted
Problem: Alveolar Overdistention

27. Acute Lung Injury ( ALI )
Damage to the Lung :Damage to the Lung :
Not distributed homogeneouslyNot distributed homogeneously
Even in severe cases ~ 1/3 lung is openEven in severe cases ~ 1/3 lung is open
Open lung receives the entire tidal Open lung receives the entire tidal
volume resulting in :volume resulting in :
OverdistensionOverdistension
Local hyperventilationLocal hyperventilation
Inhibition of surfactantsInhibition of surfactants
Ravenscraft, Sue. Respiratory Care,
Vol 41, No 2 : 105-111, Feb 1996

28. ALI and ARDS
Non-Homogeneous Lung Units
Collapsed
Recruitable
Normal
Lung Units
Fig 8.8

29. ALI and ARDS
Effect of Volume Ventilation
Set V
T
Collapsed
Recruitable
Normal
Lung Units
Fig 8.9

30. Overdistension
V
o
lu
m
e

(
m
l)
Pressure (cm H
2
O)
Little or no change in V
T
Little or no change in V
T
P
aw

rises
P
aw

rises
Normal
Abnormal
Fig 8.10

31. VOLUME TARGETED VENTILATION
Delivered Tidal Volume is ConstantDelivered Tidal Volume is Constant
Better Control on PaCOBetter Control on PaCO
22
Higher risk of Ventilator-induced Lung InjuryHigher risk of Ventilator-induced Lung Injury
PP
alv alv may Increasemay Increase
Potential for local Alveolar Over-distentionPotential for local Alveolar Over-distention
May promote patient-ventilator dyssynchrony May promote patient-ventilator dyssynchrony
and increased WOBand increased WOB

32. ARDS network.
N Eng J Med 2000, 342(18):1301-1308.
Multi-center NIH study demonstrated that
ALI/ARDS patients ventilated with tidal
volumes of 6 ml/Kg were significantly more
likely to survive than those ventilated with
tidal volumes of 12 ml/Kg.

33. Over-distention
Observed on a Pressure-Volume LoopObserved on a Pressure-Volume Loop
Indicates hyperinflation or excessive Indicates hyperinflation or excessive
application of pressureapplication of pressure
May promote BarotraumaMay promote Barotrauma
Corrective action includes reduction in the Corrective action includes reduction in the
Peak Inspiratory Pressure or Tidal VolumePeak Inspiratory Pressure or Tidal Volume

34. Ventilator-induced Lung Injury
Occurs as a result of:
■ Over-distention of alveoli
■ Repetitive opening and closure of lung units
throughout the respiratory cycle

35. In ALI and ARDS, Volume Ventilation
seems to be detrimental
ADVANCEMENT: Pressure Targeted Ventilation

36. ALI and ARDS
Non-Homogeneous Lung Units
Collapsed
Recruitable
Normal
Lung Units
Fig 8.11
Pre set Pressure

37. PRESSURE TARGETED VENTILATION
PIP and PPIP and P
alvalv are Limited are Limited

Prevents Alveolar Over-distentionPrevents Alveolar Over-distention

Provides better Patient-Ventilator Provides better Patient-Ventilator
synchronysynchrony

Delivered Tidal Volume depends on Delivered Tidal Volume depends on
Airway Resistance and Lung ComplianceAirway Resistance and Lung Compliance
Tidal Volume and PaCOTidal Volume and PaCO
22 are variable are variable

38. Pressure Control Ventilation
Flow
Time
TIME
CYCLING
T
I

39. Assisted Mode
(Pressure-Targeted Ventilation)
Pressure
Flow
Volume
(L/min)
(cm H
2
O)
(ml)
Set PC level
Time (sec)Time (sec)
Time-Cycled
Patient Triggered, Pressure Limited, Time Cycled Ventilation

40. Assisted Mode
(Volume-Targeted Ventilation)
Assisted Mode
(Volume-Targeted Ventilation)
Time (sec)Time (sec)
Flow
L/m
Pressure
cm H
2
O
Volume
mL
Preset V
T
Volume Cycling
Patient triggered, Flow limited, Volume cycled Ventilation
Assisted Mode
(Pressure-Targeted Ventilation)
Assisted Mode
(Pressure-Targeted Ventilation)
Pres s ure
Flow
Vo lume
(L/min)
(cm H
2
O)
(ml)
Set PC level
T ime (s ec)T ime (s ec)
Time-Cycled
Patient Triggered, Pressure Limited, Time Cycled Ventilation
Scalars in Assisted Mode
FIGURE 1

41. ARDS
Recruitable
Collapsed
Normal
Pressure Augmented Breath
P
P
P

42. ARDS

Resolved

43. ARDSnet Findings
Lower Tidal Volumes

Use of rapid rates avoiding auto-PEEP ( < 35/min )
P
PLAT
< 30 cm H
2
O reduces mortality
Lower P
PLAT
showed better outcome
ARDSnet: 6ml/kg reduces mortality vs. 12 ml/kg

44. Strategies to Ventilate ALI and ARDS patients
Prevent Alveolar Over-distention
 Use of low Tidal Volumes (5-7 ml/Kg)
 May promote de-recruitment of alveoli
Prevent repetitive alveolar opening and closure
 Use of Recruitment Maneuver
 sustained increase in airway pressure
 application of adequate end-expiratory pressure
(PEEP/CPAP)

45. Efforts made to prevent de-recruitment
Application of PEEP
Use of Inverse Ratio Ventilation with PEEP
Use of Airway Pressure Release Ventilation
(APRV) or BiLevel Ventilation

46. Saura P, Blanch L. How to set Positive
End-Expiratory Pressure.
Respir Care 2002; 47 (3): 279-295
Overdistention and repetitive opening and
closing of alveolar units seem to contribute
to progressive lung injury.

47. We want to maintain spontaneous breathing,
protect the lungs from high alveolar pressures
and deliver the set Tidal Volume.
ADVANCEMENT: Dual Ventilation with closed Looping

48. Initiation of Mechanical Ventilation
Volume Ventilation Pressure Ventilation
Dual Ventilation

49. COMBINED PRESSURE/VOLUME
VENTILATION
Exploit beneficial effects of both Exploit beneficial effects of both
Pressure and Volume VentilationPressure and Volume Ventilation
Improve Patient-ventilator SynchronyImprove Patient-ventilator Synchrony
Prevent ventilator induced lung injuryPrevent ventilator induced lung injury

51. Closed-loop Ventilation
Volume Assured Pressure Support Ventilation (VAPS)
Pressure Augmentation ( P
Aug
)
Volume Support ( VS )
Pressure Regulated Volume Control ( PRVC,
Autoflow,
VC+ )
Adaptive Support Ventilation ( ASV )
Proportional Assist Ventilation ( PAV )

52. PRVC
Trigger On
Exhaled VT< Set VT
Exhaled VT >Set VT
Pressure Support level
increases stepwise
until
Exhaled VT = Set VT
Pressure Support level
decreases stepwise
until
Exhaled VT = Set VT

53. To recruit alveoli, mean airway pressure
needs to be increased without causing
Overdistension.
ADVANCEMENT: Newer modes APRV and BiLevel

54. Amato MB., et al., Effect of a protective-ventilation
strategy on mortality in ARDS.
N Eng J Med 1998;338(6):347-354
Initial recruitment of alveolar units may be
achieved by applying PEEP at a level above
the lower inflection point of the P-V curve.

55. V
o
lu
m
e

(
m
l)
PEEP > 2-3 cm H
2
O above LIP
Lung Protective Strategy
Pressure

56. Inflection Points
Lower Inflection
Point (LIP or P
flex
)
Upper Inflection
Point
Volume
Pressure

57. Airaway Pressure Release Ventilation
(APRV)

58. Upper And Lower Inflection Points
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH
2
O
V
T
Alveolar collapse
P
T
Lower inflection points are thought to be a point of critical opening pressure

59. Upper And Lower Inflection Points
0 20 40 602040-60
0.2
LITERS
0.4
0.6
Paw
cmH
2
O
V
T
Alveolar overdisention
Alveolar collapse
P
T

63. Possible Approaches to Ventilate ARDS Patients
APRV
PCIRV
BiLevel or BiVent
PRVC
HFO
No data to indicate that any mode of ventilation
is BETTER than conventional Pressure-A/C
ventilation

64. Advances in Mechanical Ventilation
Control,
Assist,
PEEP,
CPAP
IMV,
SIMV,
PSV,
PCV,
Combinations of
Volume or Pressure
ventilation:
SIMV +PSV,
SIMV+PSV+CPAP
VENTILATOR
GRAPHICS
CLOSED-LOOP
VENTILATION
VAPS, Paug
VS, PRVC,
ASV,

,
PAV, APRV,


Fig 7.4

65. Other Supportive Advancements

67. Inspiratory Time

68. PSV Flow-Cycle Criteria
F
l
o
w
T
Peak Inspiratory Flow
5%
20%
40%

69. THANK YOU!