1. Advanced Modes of Mechanical Ventilation
Mazen Kherallah, MD, FCCP

2. Points of Discussion Triggered Modes of Ventilation
Volume Support (VS)
Proportional Assist Ventilation (PAV or PPS)
Hybrid Modes of Ventilation
Volume Assured Pressure Support
Pressure Regulated Volume Control (PRVC)
Auto mode: VS and PRVC
Adaptive Support Ventilation: ASV
Bi-level Ventilation (APRV and Bi-vent)
Mandatory Minute Ventilation (MMV)

3. Pressure Limited Flow Cycled Ventilation
Dual Control Breath-to-Breath pressure-limited flow-cycled ventilation Volume Support
Control
Trigger
Limit
Target
Cycle
Pressure
Patient
Volume
Flow
Pressure Limited Flow Cycled Ventilation

4. VS (Volume Support)
Apnea
Upper Pressure limit
5 cm H2O
Pressure
5 cm H2O 1 2 3 4 5 6
Flow
Constant exp. Flow
(1), VS test breath (5 cm H2O); (2), pressure is increased slowly until target volume is achieved; (3), maximum available pressure is 5 cm H2O below upper pressure limit; (4), VT higher than set VT delivered results in lower pressure; (5), patient can trigger breath; (6) if apnea alarm is detected, ventilator switches to PRVC

5. yes
Volume from
Ventilator=
Set tidal volume
Calculate new
Pressure limit no
Calculate
compliance
Flow= 5% of
Peak flow
yes
Trigger
Pressure limit
Based on VT/C
Cycle off no
Control logic for volume support mode of the servo 300

6. Pressure Limited Flow Cycled Ventilation
Dual control breath to breath: Proportional Assist Ventilation(PAS)/Proportional Pressure Support (PPS)
Control
Trigger
Limit
Target
Cycle
Pressure
Patient
Volume
Flow
Pressure Limited Flow Cycled Ventilation

7. Proportional Assist Ventilation (PAV)
Changing pressure support based on patient’s efforts
Pressure
Time
Flow
Time
Rregulates the pressure output of the ventilator moment by moment in accord with the patient’s demands for flow and volume.
Thus, when the patient wants more, (s)he gets more help; when less, (s)he gets less. The timing and power synchrony are therefore nearly optimal—at least in concept.

8. Proportional Assist Amplifies Muscular Effort
Muscular effort (Pmus) and
airway pressure assistance
(Paw) are better matched for Proportional Assist (PAV) than for Pressure Support (PSV).

10. Dual Control within a Breath volume-assured pressure support
Trigger
Limit
Target
Cycle
Dual
Pressure/
Volume
Patient
Pressure
Flow or volume
Volume Assured Pressure Support Ventilation

11. Switch from Pressure control to
Pressure limit
overridden
Switch from Pressure control to
Volume/flow control 40
Set pressure limit P aw
cmH 2
-20
0.6
Set tidal volume cycle threshold
Tidal volume
met
Tidal volume
not met
Volume L
Inspiratory flow
greater than set flow 60
Inspiratory flow
equals set flow
Flow cycle
Set flow
Flow
L/min 60

12. Control logic for volume-assured pressure-support mode
Trigger
Pressure at
Pressure support no
delivered VT
≥ set VT
flow=
25% peak
yes
yes no
Insp flow
> Set flow
Cycle off
inspiration
yes no
Switch to flow control
at peak flow setting no
delivered VT
= set VT
PAW <PSV
setting
yes no
yes
Control logic for volume-assured pressure-support mode

13. Dual Control Breath-to-Breath Pressure Regulated Volume Control
Trigger
Limit
Target
Cycle
Volume
Patient or Time
Pressure
Lowest pressure
for set volume
Time
Pressure-limited Time-cycled Ventilation

14. PRVC (Pressure Regulated Volume Control)
Upper Pressure Limit
Pressure
5 cm H2O
Time 1 2 3 4 5 6
Floe
Time
PRVC. (1), Test breath (5 cm H2O); (2) pressure is increased to deliver set volume; (3), maximum available pressure; (4), breath delivered at preset E, at preset f, and during preset TI; (5), when VT corresponds to set value, pressure remains constant; (6), if preset volume increases, pressure decreases; the ventilator continually monitors and adapts to the patient’s needs

15. PRVC Automatically Adjusts To Compliance Changes
Pressure control Ventilation
PRVC

16. Trigger yes Volume from Ventilator= no Set tidal volume Calculate new
Pressure limit
Calculate
compliance
Time= set
Inspiratory time
yes
Trigger
Pressure limit
Based on VT/C
Cycle off no
Control logic for pressure-regulated volume control and autoflow

17. Automode Mandatory Spontaneous PRVC VS
Ventilator triggered, pressure controlled and time cycled; the pressure is adjusted to maintain the set tidal volume
Patient triggered, pressure limited, and flow cycled.
Apnea for 12 seconds
Two consecutive breaths

18. Dual Control Breath-to-Breath adaptive support ventilation

19. ASV (Adaptive Support Ventilation)
A dual control mode that uses pressure ventilation (both PC and PSV) to maintain a set minimum E (volume target) using the least required settings for minimal WOB depending on the patient’s condition and effort
It automatically adapts to patient demand by increasing or decreasing support, depending on the patient’s elastic and resistive loads

20. ASV (Adaptive Support Ventilation)
The clinician enters the patient’s IBW, which allows the ventilator’s algorithm to choose a required E. The ventilator then delivers 100 mL/min/kg.
A series of test breaths measures the system C, resistance and auto-PEEP
If no spontaneous effort occurs, the ventilator determines the appropriate respiratory rate, VT, and pressure limit delivered for the mandatory breaths
I:E ratio and TI of the mandatory breaths are continually being “optimized” by the ventilator to prevent auto-PEEP
If the patient begins having spontaneous breaths, the number of mandatory breaths decrease and the ventilator switches to PS at the same pressure level
Pressure limits for both mandatory and spontaneous breaths are always being automatically adjusted to meet the E target

21. The Safety Window: low rate/volume limitsmL
Target +
Current
800
(Pmax-PEEP)*Cdyn
600
5 b/min
MinVol 7.0 L/min
f=60/[1RCinsp+2RCexp] +
400
2 * Vd
200 f
b/min 10 20 30 40 50 60
fSpont
0 b/min
fControl
11 b/min
Pinsp
18 cmH2O

22. Mandatory Minute Ventilation
A minimum minute ventilation is set by the operator
The ventilator monitors the spontaneous MV
The part of the pre-selected MV that the patient is not able to accomplish is provided by the ventilator to make up the difference by automatically changing the breath rate

23. MMV
Min.Vent.
MMV
SMV
time

24. MMV Settings
MMV = 70-90% of SMV
Min.Vent.
MMV
SMV
time

25. BiLevel Ventilation P 1 2 3 4 5 6 7 Pressure Support PEEPHigh + PS aw
cmH 2 60
-20
PEEPH
PEEPL

26. Thigh
Pressure
Tlow
Phigh
Plow
Time
Pressure
Psupp
Time

27. Thigh
Pressure
Tlow
Phigh
Plow
Time
Pressure
Psupp
Phigh
Time

28. Thigh
Pressure
Tlow
Phigh
Plow
Time
Pressure
Psupp
Psupp
Phigh
Time

29. Airway Pressure Release Ventilation
Control
Trigger
Limit
Cycle
Pressure
Time
Time Triggered Time-cycled Ventilation

30. Airway Pressure Release Ventilation
Spontaneous Breaths 60 P aw
cmH 2
Releases
-20

31. APRV (Airway Pressure Release Ventilation)
Spontaneous breaths
CPAP Released
CPAP Restored
CPAP Level
Airway Pressure
CPAP Level 1
CPAP Level 2
Time

33. Questions