The Clinical Effect of an Early, Protocolized Approach to Mechanical Ventilation for Severe and Refractory Hypoxemia

ARDS remains a source of significant morbidity and mortality in the critically ill patient. The mainstay of therapy entails invasive mechanical ventilation utilizing a lung-protective strategy designed to limit lung injury associated with excessive stress and strain while the underlying etiology of respiratory failure is identified and treated. Less is understood about what to do once conventional ventilation parameters have been optimized but the patient's respiratory status remains unchanged or worsens. In 2015, a protocolized, stepwise approach to mechanical ventilation with partially automated and clearly defined thresholds for management changes was implemented at our institution. We hypothesized that, by identifying appropriate patients earlier, time-to-escalation and rescue therapy implementation would be shortened.

Subjects with severe ARDS, treated with prone positioning based on our institution's protocolized approach from December 2013 to August 2016 were included. Their baseline characteristics, severity of illness scores, and mechanical ventilation parameters were collected and analyzed.

Baseline characteristics, tidal volumes, P_aO /F_IO , duration of ventilation after proning, and mortality were similar in both groups. Median (interquartile range [IQR]) PEEP at the time of proning was higher after the protocol implementation (12.5 cm H₂O [IQR 6.5-19.4] vs 18 cm H₂O [IQR 10-22], P = .386), and mean (IQR) respiratory system driving pressure was lower (16 cm H₂O [IQR 13-36.2] vs 12 cm H₂O [IQR 9-19.6], P = .029). Median (IQR) time from refractory hypoxemia identification to proning was shorter after protocol implementation (42.2 h [IQR 6.83-347.2] vs 16.3 h [IQR 1-99.7], I = .02), and P_aO /F_IO at 1 h after proning was higher. ICU and hospital LOS were shorter after the protocol implementation.

Following the implementation of an early, evidence-based, protocolized approach to optimizing mechanical ventilation, subjects with true refractory hypoxemia were identified earlier and time to proning was significantly shorter. Despite improvement in the evaluation and management of refractory hypoxemia as well as time to initiation of prone positioning, mortality was unchanged and there was variation in the duration of the position.