Lung Recruitment and Titrated PEEP in Moderate to Severe ARDS

Abstract

Mechanical ventilation is critical for the survival of many patients with the acute respiratory distress syndrome (ARDS) but can also cause ventilator-induced lung injury (VILI). One form of VILI occurs when the lungs exhale to relatively low volumes and airway pressures. This may cause injurious tidal closing and reopening of small bronchioles and alveoli or excessive stress at the margins between aerated and atelectatic airspaces. 1,2 In animal studies, positive end-expiratory pressure (PEEP) reduced or prevented VILI from exhalation to low volumes and pressures. 1,[3][4][5] PEEP can also recruit some previously atelectatic or fluid-filled lung regions, allowing more of the lung to be available for inflation during inspiration. This could reduce VILI from overdistention of an otherwise reduced amount of aerated lung.In some early studies, the levels of PEEP that were applied for lung protection exceeded the levels that most clinicians use when managing patients with ARDS. This led to recommendations to use higher PEEP in patients with ARDS to minimize low volume and low pressure VILI and hopefully to improve clinical outcomes. The "open lung approach" (OLA) aims to achieve high levels of lung aeration in patients with ARDS by first conducting recruitment maneuvers (RMs) to reverse atelectasis and then applying high levels of PEEP to keep recruited alveoli open. 6 Recruitment maneuvers typically involve a ventilatory approach that transiently increases pulmonary airway pressure to reopen recruitable lung areas. For example, an RM can be conducted by raising inspiratory airway pressures to 50 cm of H 2 O for 1 or 2 minutes. However, 3 large randomized clinical trials of higher PEEP and RMs in patients with ARDS and a Pao 2 /Fio 2 ratio of 300 or less did not demonstrate significant reductions in mortality. [7][8][9] An individual patient data meta-analysis of these 3 clinical trials suggested that higher PEEP reduced mortality in patients with more severe hypoxemia (Pao 2 /Fio 2 ≤200), but this

Treatment for severe acute respiratory distress syndrome from COVID-19

“…If the patient is not responding to adjustment of the level of positive end-expiratory pressure, additional strategies might stabilise them. Recruitment manoeuvres probably have little value, 6 but moderate pressures of approximately 30 cm H 2 O for 20-30 s can be applied in the presence of a physician to monitor haemodynamics. If there is no improvement in oxygenation or driving pressure, or if the patient develops hypotension or barotrauma, the recruitment manoeuvres should be discontinued.…”

Acute Respiratory Distress Syndrome

“…RMs remind clinician, not only severity of ARDS, but lung recruitability, phase of ARDS, recruitment pressure limitation, and hemodynamic stability should also be considered. [ 29 ]…”

Longitudinal PEEP Responses Differ Between Children With ARDS and at Risk for ARDS

“…4 Strain and stress should be readily estimated and ventilator settings appropriately individualized to properly set the mechanical breath and further eliminate the possibility of ventilator-induced lung injury. 5 There is little evidence indicating optimal ventilation practices for pediatric ARDS, and ventilation practices are mainly based on institutional preferences, personal beliefs, and clinical data extrapolated from adult patients with ARDS. Low V T has been shown to minimize tidal over-distention (volutrauma), and higher PEEP levels are used to reduce cyclic closing and reopening of alveoli (atelectrauma).…”