Advanced Modes of Mechanical Ventilation. P OINTS OF D ISCUSSION Triggered Modes of Ventilation...
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Transcript of Advanced Modes of Mechanical Ventilation. P OINTS OF D ISCUSSION Triggered Modes of Ventilation...
Advanced Modes of Mechanical Ventilation
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)
DUAL CONTROL BREATH-TO-BREATHPRESSURE-LIMITED FLOW-CYCLED VENTILATIONVOLUME SUPPORT
Control Trigger Limit Target Cycle
Pressure Patient Pressure Volume Flow
Pressure Limited Flow Cycled Ventilation
VS (VOLUME SUPPORT)
(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
1 2 3 4 5 6
Pressure Upper Pressure limit
5 cm H2O
Flow
Apnea5 cm H2O
Constant exp. Flow
Volume fromVentilator=
Set tidal volume
Pressure limitBased on VT/C
Cycle off
Calculatecompliance
Calculate newPressure limit
no
yes
yes
no
Control logic for volume support mode of the servo 300
Trigger Flow= 5% ofPeak flow
DUAL CONTROL BREATH TO BREATH:PROPORTIONAL ASSIST VENTILATION(PAS)/PROPORTIONAL PRESSURE SUPPORT (PPS)
Control Trigger Limit Target Cycle
Pressure Patient Pressure Volume Flow
Pressure Limited Flow Cycled Ventilation
PROPORTIONAL ASSIST VENTILATION (PAV)
Pressure
Flow
Time
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.
Changing pressure support based on patient’s efforts
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).
DUAL CONTROL WITHIN A BREATHVOLUME-ASSURED PRESSURE SUPPORT
Control Trigger Limit Target Cycle
DualPressure/Volume
Patient Pressure Volume Flow or volume
Volume Assured Pressure Support Ventilation
PPawaw
cmHcmH2200
6060
-20-20
6060
FlowFlowL/minL/min
VolumeVolume
Set flow
Set tidal volume cycle threshold
Set pressure limit
Tidal volume met
Tidal volume not met
Switch from Pressure control toVolume/flow control
Inspiratory flowgreater than set flow
Flow cycleInspiratory flowequals set flow
Pressure limitoverridden
LL
0
0.6
4040
Pressure at Pressure support
delivered VT
≥ set VT
flow= 25% peak
Cycle offinspiration
Insp flow> Set flow
PAW <PSVsetting
delivered VT
= set VT
Switch to flow controlat peak flow setting
Trigger
yes
no
no
no
no
no
yes
yes
yes
Control logic for volume-assured pressure-support mode
yes
DUAL CONTROL BREATH-TO-BREATHPRESSURE REGULATED VOLUME CONTROL
Control Trigger Limit Target Cycle
Volume Patient or Time
Pressure Lowest pressurefor set volume
Time
Pressure-limited Time-cycled Ventilation
PRVC (PRESSURE REGULATED VOLUME CONTROL)
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
1 2 3 4 5 6
Upper Pressure Limit5 cm H2OPressure
Floe
Time
Time
PRVC AUTOMATICALLY ADJUSTS TO COMPLIANCE CHANGES
Pressure control Ventilation PRVC
Volume fromVentilator=
Set tidal volume
Time= setInspiratory time
Pressure limitBased on VT/CTrigger Cycle off
Calculatecompliance
Calculate newPressure limit
no
yes
yes
no
Control logic for pressure-regulated volume control and autoflow
AUTOMODE
Mandatory Spontaneous
PRVC VSVentilator 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
DUAL CONTROL BREATH-TO-BREATHADAPTIVE SUPPORT VENTILATION
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
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
+
+Target
Current
MinVol 7.0 L/min
200
400
600
800
THE SAFETY WINDOW: LOW RATE/VOLUME LIMITS
VmL
10 20 30 40 50 60
fSpont
0 b/min
fControl
11 b/min
Pinsp
18 cmH2O
fb/min
5 b/min
2 * Vd
(Pmax-PEEP)*Cdyn
f=60/[1RCinsp+2RCexp]
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
MMV
time
Min.Vent.
MMVMMV
SMVSMV
MMV SETTINGS
time
Min.Vent.
SMVSMVMMVMMV
MMV = 70-90% of SMVMMV = 70-90% of SMV
BILEVEL VENTILATION
PEEPPEEPHH
PEEPPEEPLL
Pressure SupportPressure SupportPEEPPEEPHigh High + PS + PS
PPawaw
cmHcmH2200
6060
-20-201 2 3 4 5 6 7
Thigh
Tlow
Plow
Phigh
Time
Time
Pre
ssu
reP
ress
ure
Psupp
Thigh
Tlow
Plow
Phigh
Time
Time
Pre
ssu
reP
ress
ure
Phigh
Psupp
Thigh
Tlow
Plow
Phigh
Time
Time
Pre
ssu
reP
ress
ure
PhighPsupp
Psupp
AIRWAY PRESSURE RELEASE VENTILATION
Control Trigger Limit Cycle
Pressure Time Pressure Time
Time Triggered Time-cycled Ventilation
AIRWAY PRESSURE RELEASE VENTILATION
PPawaw
cmHcmH2200
6060
-20-201 2 3 4 5 6 7 8
Spontaneous Breaths
Releases
APRV (AIRWAY PRESSURE RELEASE VENTILATION)
Spontaneous breaths
CPAP Level
CPAP Level 2
CPAP Level 1
CPAP ReleasedCPAP Restored
Time
Air
way
Pre
ssu
re
QUESTIONS