APRV

Definition

APRV lung demonstration video

APRV Quick Reference Sheet

APRV Review: Habashi CCM 2005

Primary Indications

Relative Contraindications

Parameters

Initial Settings

1) P high at the P plateau (or desired . P mean + 3cm H2O). Try to keep P high below 30-35 cm H2O

2) T high at 4-6 seconds

3) P low at 0 (to optimize expiratory flow)

4) T low at 0.5 to 0.8 seconds: Adjust the T low to cut off the expiratory flow during a release at about 50% of peak expiratory flow (see figure below). Do not allow the termination of expiratory flow to go <25% of the peak expiratory flow rate. This intrinsic PEEP allows P low to be set at 0 without causing derecruitment. T low can be as low as 0.3 seconds (closer to 75% peak expiratory flow rate) in restrictive lung disease and as high as 1.5 seconds (closer to 25% peak expiratory flow rate) in obstructive diseases. 

5) ATC (automatic tube compensation) or PS for spontaneous breaths

Titration

Hypercarbia:

Delta P (P high- P low) determines flow out of the lungs and volume exchange. Hence:

1) Decrease T high in 0.5 second increments. Shorter T high means more releases/min. (should generally not decrease to <4seconds)

2) Increase P high to increase delta P and volume exchange by increments of 2-3 cm H2O. Monitor Vt and P high

3) Check T low. If possible, increase T low to allow more time for alveolar emptying while keeping expiratory flow greater than 25% of peak expiratory flow rate. 

Hypocarbia:

1) Increase T high (fewer releases) in increments of 0.5 seconds

2) Decrease P high to lower delta P (monitor oxygenation and avoid derecruitment)

Hypoxia:

1) Increase P high in increments of 2 cm H20 to improve mean airway pressure

2) Decrease T low to be closer to 75% peak expiratory flow rate

Weaning:

When FiO2 is below 50%, recruitment maximized, and patient is breathing spontaneously, continuous gradual wean can begin by:

1) Decrease P high by 1-2 cm H2O AND increasing T high by 0.5 seconds for every 1 cm H20 drop in p high (drop and stretch)

2) Drop and stretch every 2 hours as tolerated. P mean gradually lowered so will need to monitor SpO2.

3) When P high reaches 10 cm H20 and T high reaches 12-15 seconds, change the mode to CPAP with PEEP at 10 and PS at 5-10 (ATC off). 

Evidence

From Ganesan et al (AJRCCM 2018)