Airway Pressure Release Ventilation: What Do We Know?

Abstract

Airway pressure release ventilation (APRV) is inverse ratio, pressure controlled, intermittent mandatory ventilation with unrestricted spontaneous breathing. It is based on the principle of open lung approach. It has many purported advantages over conventional ventilation, including alveolar recruitment, improved oxygenation, preservation of spontaneous breathing, improved hemodynamics, and potential lung-protective effects. It has many claimed disadvantages related to risks of volutrauma, increased work of breathing, and increased energy expenditure related to spontaneous breathing. APRV is used mainly as a rescue therapy for the difficult to oxygenate patients with acute respiratory distress syndrome (ARDS). There is confusion regarding this mode of ventilation, due to the different terminology used in the literature. APRV settings include the "P high," "T high," "P low," and "T low". Physicians and respiratory therapists should be aware of the different ways and the rationales for setting these variables on the ventilators. Also, they should be familiar with the differences between APRV, biphasic positive airway pressure (BIPAP), and other conventional and nonconventional modes of ventilation. There is no solid proof that APRV improves mortality; however, there are ongoing studies that may reveal further information about this mode of ventilation. This paper reviews the different methods proposed for APRV settings, and summarizes the different studies comparing APRV and BIPAP, and the potential benefits and pitfalls for APRV.

Airway Pressure Release Ventilation and High-Frequency Oscillatory Ventilation: Potential Strategies to Treat Severe Hypoxemia and Prevent Ventilator-Induced Lung Injury

“…Therefore, whenever a lung-protective strategy has to be chosen, it is advisable to consider the specific effects of each different method on V T and its variability. Relative contraindications to APRV include patients with obstructive lung disease (asthma exacerbations or COPD), 31 and it has never been rigorously investigated in patients with neuromuscular disease.…”

Effect of setting high APRV guided by expiratory inflection point of pressure-volume curve on oxygen delivery in canine models of severe acute respiratory distress syndrome

“…Spontaneous breath was not only able to reduce sedative dose, but also the pressure to intrathoracic heart and great vessels by increased airway pressure. This may promote venous return, increase CO 2 and DO 2 , and improve organ perfusion (19). …”

The Use of Paralytics in Patients with Acute Respiratory Distress Syndrome

“…Finally, APRV has potential disadvantages, such as the increase of work of breathing associated with important respiratory efforts that may increase the transcapillary pressure gradient, thus enhancing pulmonary edema formation or the increase in tidal volumes with potential increase in VILI. 51 The results of the BiRDS study (NCT01862016), which compares a strategy using a short period of controlled ventilation with rapid transition to APRV with a strategy using prolonged controlled ventilation, will certainly introduce new results to the debate concerning SB in ARDS.…”