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 ControlDual Control Concept

Volume Control

Decreased Compliance

Maintained VT

Higher Pressure

Pressure Control

Decreased Compliance

Lower VT

Same Pressure

Dual Control

PRVC Automatically Adjusts To Compliance ChangesPRESSURE CONTROL VENTILATION PRVC

Pressure RegulationThe 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

Measure VT

Compareto set VT

Same inspiratorypressure

inspiratorypressure

inspiratorypressure

Test breath

Less

Equal

More

PRVC

Set Minimum respiratory rate Target tidal volume Upper pressure limit:▪ Maximum delivered pressure = 5 cm H2O below

pressure alarm limit FIO2 Inspiratory time or I:E ratio Rise time PEEP

Dual Control Breath-to-BreathPressure Regulated Volume Control

Control Trigger Limit Target CycleVolume Patient or

TimePressure 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

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

PRVCThe Mode on Different Ventilators

PRVC in Servo i

Pres

sure

Flow

Volu

me

PRVC

Pres

sure

Flow

Volu

me

Upper Pressure limit5 cm H2O

Pressure Regulation in Drager

Pressure Regulation in CMV

Pressure Limit in Autoflow

PRVCIndications, 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

Thank You