Mechanical Breath Profile of Airway Pressure Release Ventilation

Abstract

In patients with acute lung injury, mechanical ventilation is a lifesaving treatment. However, mechanical ventilation may cause a secondary ventilator-induced lung injury (VILI) exacerbating the original acute lung injury. Several mechanisms of VILI have been described, including pressure gradient–induced tissue trauma from repetitive alveolar collapse and expansion, also known as atelectrauma^1,2 and alveolar overdistention (volutrauma).³ Alveolar heterogeneity and instability exacerbate these mechanisms. Despite implementation of ventilation strategies to protect against both atelectrauma and volutrauma, mortality from acute respiratory distress syndrome (ARDS) remains unacceptably high.^4,5 Protti et al⁶ developed a technique of measuring whole-lung stress or strain and demonstrated that dynamic lung strain was more injurious than static strain. Their data suggest a novel method of determining the effects of the different components that compose the mechanical breath profile (MBP), including volumes, flows, pressures, rates, and the time that these forces are applied, on lung pathology. This knowledge may be used to optimize protective ventilation and reduce VILI.⁷ However, acute lung injury causes a heterogeneous injury such that whole-lung strain may not accurately reflect regional lung strain given the interdependence of alveolar architecture.⁸