PRVC Mode Workshop Objectives Understand the dual control

PRVC Mode Workshop

Objectives �Understand the dual control concept �Understand the pressure regulation mechanism in PRVC �Demonstration of PRVC �Settings and adjustment with Servo i and Dragger �Indications, advantages and disadvantages

Volume vs Pressure Control Dual Control Concept

Volume Control Decreased Compliance Higher Pressure Maintained VT

Pressure Control Decreased Compliance Lower VT Same Pressure

Dual Control

PRVC Automatically Adjusts To Compliance Changes PRESSURE CONTROL VENTILATION PRVC

Pressure Regulation The Concept

PRVC �Assist-control ventilation �Pressure control titrated to a set tidal volume �Time cycled

Assist control �Breaths: Ventilator initiated (control breaths) Patient initiated (assist breaths) Set minimum frequency �Characteristics of each inspiration are the same Not affected by whether breath is control breath or an assist breath

Assist control �Set Minimum respiratory rate ▪ Patient’s spontaneous respiratory rate < set rate ventilator gives additional control breaths to make up difference ▪ Patient’s spontaneous rate > set rate no control breaths

PRVC �Set Minimum respiratory rate Target tidal volume

PRVC Test breath Measure VT More Compare to set VT Less Equal inspiratory pressure Same inspiratory pressure

PRVC �Set Minimum respiratory rate Target tidal volume Upper pressure limit: ▪ Maximum delivered pressure = 5 cm H 2 O below pressure alarm limit FIO 2 Inspiratory time or I: E ratio Rise time PEEP

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

PRVC (Pressure Regulated Volume Control) Upper Pressure Limit Pressure Floe 1 5 cm H 2 O 2 3 4 5 6 Time PRVC. (1), Test breath (5 cm H 2 O); (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

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

PRVC The Mode on Different Ventilators

Volume Flow Pressure PRVC in Servo i

PRVC Volume Flow Pressure Upper Pressure limit 5 cm H 2 O

Pressure Regulation in Drager

Pressure Regulation in CMV

Pressure Limit in Autoflow

PRVC Indications, Advantages and Disadvantages

Advantages �Decelerating inspiratory flow pattern �Pressure automatically adjusted for changes in compliance and resistance within a set range Tidal volume guaranteed Limits volutrauma Prevents hypoventilation

Disadvantages �Pressure delivered is dependent on tidal volume achieved on last breath Intermittent patient effort variable tidal volumes �Less suitable for patients with asthma or COPD

PRVC (Pressure Regulated Volume Control) DISADVANTAGES AND RISKS Varying mean airway pressure May cause or worsen auto-PEEP When patient demand is increased, pressure level may diminish when support is needed � May be tolerated poorly in awake non-sedated patients � A sudden increase in respiratory rate and demand may result in a decrease in ventilator support � � � AFVANTAGES Maintains a minimum PIP Guaranteed VT Patient has very little WOB requirement � Allows patient control of respiratory rate � Decelerating flow waveform for improved gas distribution � Breath by breath analysis � � �

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