Airway Pressure Relief Ventilation Methodology and Theory

Ron Pasewald BS, RRT, RCP Critical Care Coordinator of Respiratory Therapy Froedtert Hospital

Airway Pressure Relief Ventilation Methodology and Theory

Ron Pasewald BS, RRT, RCP Critical Care Coordinator of Respiratory Therapy Froedtert Hospital

Objectives • Provide the definitions for APRV • Explain the four set parameters. • Provide indications/contraindications for APRV • Explain the benefits of spontaneous breathing with APRV. • Recommend appropriate initial settings for APRV • Make adjustments based on arterial blood gas results • Wean ventilation with APRV

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APRV Definition • APRV is spontaneous breathing CPAP with short releases. – ~90% CPAP phase

• These short releases of pressure allows C02 release from the lungs. • Spontaneous S t breathing b thi augments t CO2 elimination and helps prevent alveolar collapse. • Diffusion is the main principle. Keeping the alveoli open allows diffusion to occur. • APRV ventilates your patients with an “Open lung” approach.

Goal of using APRV • • • •

To provide lung protective ventilation To provide an “Open lung” approach Minimize alveolar over distension. Avoid repeated alveolar collapse and reexpansion. i • Restore FRC through recruitment • Maintain FRC by creating intrinsic PEEP.

Open lung model

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Indications • Primarily used as an alternative ventilation technique in patients with ARDS. • Used to help protect against ventilator induced lung injury. injury • New data from Dr. Habashi et al, shows that APRV may help prevent ARDS in Shock Trauma patients.

ARDS Definition • ARDSnet criteria: – Bilateral Infiltrates – PaO2/FIO2 ratio < 300 and falling – Plateau pressures greater than 30 cm H2O – No evidence of left heart failure

ARDS Process

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ARDS Mortality Rate

Trauma ARDS rate Dr. Habashi/Shock Trauma

APRV: Relative Contraindications • Unmanaged increased intracranial pressure. • Large proximal bronchopleural fistulas. • Obstructive lung diseases? – Set that TLow correctly. Lung diseases with expiratory flow resistance needs a longer T low. – TLow needs to be set between 50 and 75% of the expiratory flow…for all patients.

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APRV Settings: Definitions • PHigh – the upper CPAP level. • PLow – the lower CPAP level. *P P High – P Low = Δ P

• Thigh – the inspiratory time phase for the PHigh. • Tlow – the expiratory time phase for PLow. * T High + T low is the set cycle time.

Pressure time waveform APRV

Initial Settings P high 20-30 cm H2O, according to the following chart. P/F