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Advanced Modes of Mechanical Ventilation

Advanced Modes of Mechanical Ventilation

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Advanced Modes of Mechanical Ventilation

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  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. Dual Control Breath-to-Breathpressure-limited flow-cycled ventilationVolume Support Pressure Limited Flow Cycled Ventilation

  4. 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

  5. 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

  6. Dual control breath to breath:Proportional Assist Ventilation(PAS)/Proportional Pressure Support (PPS) 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).

  9. Dual Control within a Breathvolume-assured pressure support Volume Assured Pressure Support Ventilation

  10. 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

  11. 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

  12. Dual Control Breath-to-BreathPressure Regulated Volume Control Pressure-limited Time-cycled Ventilation

  13. 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

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

  15. 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

  16. Automode

  17. Dual Control Breath-to-Breathadaptive support ventilation

  18. 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

  19. 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

  20. 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

  21. 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

  22. MMV Min.Vent. MMV SMV time

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

  24. 60 P Pressure Support aw PEEPHigh + PS cmH 0 2 1 2 3 4 5 6 7 PEEPL -20 BiLevel Ventilation PEEPH

  25. Thigh Pressure Tlow Phigh Plow Time Pressure Psupp Time

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

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

  28. Airway Pressure Release Ventilation Time Triggered Time-cycled Ventilation

  29. P aw Spontaneous Breaths cmH 0 2 Airway Pressure Release Ventilation 60 Releases 1 2 3 4 5 6 7 8 -20

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

  31. Questions