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Modes of Mechanical Ventilation. Points of Discussions. Advanced Basics: Flow and Time Limit and cycling Rise Time Volume vs Pressure Control Mandatory Modes of Ventilation Controlled Mandatory Ventilation (CMV or IPPV) Triggered Modes of Ventilation
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Points of Discussions • Advanced Basics: • Flow and Time • Limit and cycling • Rise Time • Volume vs Pressure Control • Mandatory Modes of Ventilation • Controlled Mandatory Ventilation (CMV or IPPV) • Triggered Modes of Ventilation • Continuous Positive Airway Pressure (CPAP) • Pressure Support Ventilation (PSV) • Hybrid Modes of Ventilation • Assist Control Mode (A/C) • Synchronized Intermittent Mandatory Ventilation (SIMV)
CPAP and PSVV Triggered Modes of Ventilation
Spontaneous Breathing Pressure (cm H2O) Flow (L/m) Volume (mL) Time (sec)
Continuous Positive Airway Pressure(CPAP) Pressure (cm H2O) CPAP Level Flow (L/m) Volume (mL) Time (sec)
Pressure Support Ventilation(PSV) Set PS Level Pressure (cm H2O) Flow Cycling Better Efforts Longer Inspiration Flow (L/m) Volume (mL) Time (sec) Patient Triggered, Flow Cycled, Pressure limited Mode
CPAP+PSV Set PS Level Pressure (cm H2O) CPAP Level Flow Cycling Flow (L/m) Volume (mL) Time (sec) Patient Triggered, Flow Cycled, Pressure limited Mode
Triggered Modes of VentilationPressure Support Ventilation Patient Triggered Flow Cycled Ventilation
CMV or IPPV Mandatory Modes of Ventilation
Mandatory Modes of VentilationCMV Time Triggered Time Cycled Ventilation
Control Mode (Pressure-Targeted Ventilation) Time Cycling Set PC Level Pressure (cm H2O) Flow (L/m) Volume (mL) Time (sec) Time Triggered, Pressure Limited, Time Cycled Ventilation
Control Mode(Volume-Targeted Ventilation) Time Cycling Pressure (cm H2O) Dependent on CL & Raw Flow (L/m) Preset VT Volume Cycling Volume (mL) Time (sec) Time Triggered, Flow Limited, Volume Cycled Ventilation
SIMV and A/C Hybrid Modes of Ventilation
Hybrid Modes of VentilationA/C Time or PatientTriggered Time Cycled Ventilation
Assisted Mode(Volume-Targeted Ventilation) Time Cycling Pressure (cm H2O) Preset peak Flow Flow (L/m) Volume (mL) Time (sec) Patient Triggered, Flow limited, Volume Cycled Ventilation
Assisted Mode (Pressure-Targeted Ventilation) Time Cycling Set PC Level Pressure (cm H2O) Flow (L/m) Volume (mL) Time (sec) Patient Triggered, Pressure Limited, Time Cycled Ventilation
SIMV(Volume Targeted Ventilation) Pressure (cm H2O) M M M Spontaneous Breaths Flow (L/m) Volume (mL) Time (sec)
SIMV+PS(Volume Targeted Ventilation) Set PS Level Tsupp Tsynch M Pressure (cm H2O) Flow-cycled Flow (L/m) Volume (mL) Time (sec)
SIMV + PS (Pressure-Targeted Ventilation) Tsynch Tsynch Tsupp Pressure (cm H2O) Set PC Level Set PS Level Time Cycled Flow-cycled Flow (L/m) Volume (mL) Time (sec)
Hybrid Mode Ventilation: Synchronization(SIMV+PSV) M Tsynch Tsynch Tsupp Tsupp M Pressure (cm H2O) Flow (L/m) Mandatory Cycle Time Cycles Time (sec) Triggered window for supported breaths Triggered window for synchronized breaths
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 Pressure Limited Flow Cycled Ventilation
VS (Volume Support) Apnea Upper Pressure limit 5 cm H2O Pressure 5 cm H2O 6 3 4 5 2 1 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
yes Volume from Ventilator= Set tidal volume no Calculate new Pressure limit Calculate compliance Flow= 5% of Peak flow yes Pressure limit Based on VT/C Trigger Cycle off no Control logic for volume support mode of the servo 300
Dual control breath to breath:Proportional Assist Ventilation(PAS)/Proportional Pressure Support (PPS) Pressure Limited Flow Cycled Ventilation
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.
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 Volume Assured Pressure Support Ventilation
Pressure limit overridden Set pressure limit P aw cmH 0 2 Set tidal volume cycle threshold Tidal volume not met Tidal volume met Inspiratory flow greater than set flow Inspiratory flow equals set flow Flow cycle Set flow Switch from Pressure control to Volume/flow control 40 -20 0.6 Volume L 0 60 Flow L/min 60
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 yes no Control logic for volume-assured pressure-support mode
Dual Control Breath-to-BreathPressure Regulated Volume Control Pressure-limited Time-cycled Ventilation
PRVC (Pressure Regulated Volume Control) Upper Pressure Limit Pressure 5 cm H2O Time 5 4 6 3 2 1 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
PRVC Automatically Adjusts To Compliance Changes Pressure control Ventilation PRVC
yes Volume from Ventilator= Set tidal volume no Calculate compliance Calculate new Pressure limit Time= set Inspiratory time yes Trigger Pressure limit Based on VT/C Cycle off no Control logic for pressure-regulated volume control and autoflow
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
The Safety Window: low rate/volume limits V mL 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 20 10 30 40 50 60 fControl 11 b/min Pinsp 18cmH2O fSpont 0 b/min
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 Min.Vent. MMV SMV time
MMV Settings MMV = 70-90% of SMV Min.Vent. MMV SMV time
60 P Pressure Support aw PEEPHigh + PS cmH 0 2 1 2 3 4 5 6 7 PEEPL -20 BiLevel Ventilation PEEPH
Thigh Pressure Tlow Phigh Plow Time Pressure Psupp Time
Thigh Pressure Tlow Phigh Plow Time Pressure Psupp Phigh Time
Thigh Pressure Tlow Phigh Plow Time Pressure Psupp Psupp Phigh Time