APRV applies continuous positive airway pressure (CPAP) with an intermittent release phase.

First described 30 years ago.

The application of CPAP (P high) for a prolonged time (T high) maintains adequate lung volume and alveolar recruitment.

There is a time-cycled release phase to a lower set of pressure (P low) for a short period of time (T low or release time) where most of ventilation and CO2 removal occurs.

If patient has spontaneous respiratory effort, spontaneous breathing can happen at any time regardless of the ventilator cycle. If the patient has no spontaneous respiratory effort, APRV becomes typical of inverse ratio (inspiration >> expiration) pressure limited ventilation.

Applying constant high pressure (P high) for an approximately 80-90% of cycle time (T high) results in persistent application of elevated mean airway pressure (MAP). This elevated MAP allows almost allows almost constant lung recruitment (open-lung approach), in contrast to repetitive inflation and deflation of the lung using conventional ventilatory methods.

Spontaneous breathing plays an important role as it is believed to improve patient comfort and patient-ventilatory synchrony with reduction in sedation necessary.

APRV pressure and time graph

Indications:

Safe, effective mode in cases of acute lung injury, acute respiratory distress, and profound atelectasis

Initial settings:

  • P high: 20-30 cm H2O
  • P low: 0-5 cm H2O initially
  • T high: 4-6 s
  • T low: 0.2-0.8 s

Maneuvers to correct poor oxygenation:

  1. Minimize air leak
  2. Increase either P high T high, or both to increase MAP

Maneuvers to correct poor ventilation:

  1. Increase P high and decrease T high  simultaneously to increase minute ventilation while keeping stable MAP (preferred), 
  2. Increase T low by 0.05-0.1 s increments,
  3. Decrease sedation to increase pt’s effort

References:

  1. Downs JB, Stock MC. Airway pressure release ventilation: a new concept in ventilatory support. Crit Care Med. 1987;15(5):459-461.
  2. Daoud EG. Airway pressure release ventilation. Ann Thorac Med. 2007;2(4):176-179.
  3. Habashi NM. Other approaches to open-lung ventilation: airway pressure release ventilation. Crit Care Med. 2005;33(3 Suppl):S228-240.
  4. Hotchkiss JR, Jr., Blanch L, Murias G, et al. Effects of decreased respiratory frequency on ventilator-induced lung injury. Am J Respir Crit Care Med. 2000;161(2 Pt 1):463-468.
  5. Sydow M, Burchardi H, Ephraim E, Zielmann S, Crozier TA. Long-term effects of two different ventilatory modes on oxygenation in acute lung injury. Comparison of airway pressure release ventilation and volume-controlled inverse ration ventilation. Am J Respir Crit Care Med. 1994;149(6): 1550-1556.