Airway pressure release ventilation for lung protection in acute respiratory distress syndrome: an alternative way to recruit the lungs

Abstract

Purpose of review Airway pressure release ventilation (APRV) is a modality of ventilation in which high inspiratory continuous positive airway pressure (CPAP) alternates with brief releases. In this review, we will discuss the rationale for APRV as a lung protective strategy and then provide a practical introduction to initiating APRV using the time-controlled adaptive ventilation (TCAV) method. Recent findings APRV using the TCAV method uses an extended inspiratory time and brief expiratory release to first stabilize and then gradually recruit collapsed lung (over hours/days), by progressively ‘ratcheting’ open a small volume of collapsed tissue with each breath. The brief expiratory release acts as a ‘brake’ preventing newly recruited units from re-collapsing, reversing the main drivers of ventilator-induced lung injury (VILI). The precise timing of each release is based on analysis of expiratory flow and is set to achieve termination of expiratory flow at 75% of the peak expiratory flow. Optimization of the release time reflects the changes in elastance and, therefore, is personalized (i.e. conforms to individual patient pathophysiology), and adaptive (i.e. responds to changes in elastance over time). Summary APRV using the TCAV method is a paradigm shift in protective lung ventilation, which primarily aims to stabilize the lung and gradually reopen collapsed tissue to achieve lung homogeneity eliminating the main mechanistic drivers of VILI.

Pressure versus volume assist-control ventilation in Acute Respiratory Distress Syndrome: a randomised clinical trial.

“…at the two pressure levels) [9,10]. PC-SV uses the same working principles as APRV (two pressure levels, no synchronisation) but is adjusted with conventional insu ation time and respiratory rate (contrary to classical APRV set with very short expiratory time) [11] . The difference with classical pressure-assist control is that patients' efforts cannot trigger assisted breaths.…”

Inconsistent Methods Used to Set Airway Pressure Release Ventilation in Acute Respiratory Distress Syndrome: A Systematic Review and Meta-Regression Analysis

“…We chose to categorize ventilator settings into groups based on how each setting impacts lung physiology and their alignment with the preponderance of the basic science literature that has been shown to be lung-protective [10,15]. Specifically, we compared P high set by plateau pressure vs. P high not set by plateau pressure, P low set to 0 vs. P low not set to 0, T low set to 50-75% of peak expiratory flow rate vs. T low not set to 50-75% of peak expiratory flow rate, and T high set based on PaCO 2 vs. T high set arbitrarily.…”