Physiologic Effects of the Awake Prone Position Combined With High-Flow Nasal Oxygen on Gas Exchange and Work of Breathing in Patients With Severe COVID-19 Pneumonia: A Randomized Crossover Trial

To determine the effect of the awake prone position (APP) on gas exchange and the work of breathing in spontaneously breathing patients with COVID-19-associated acute hypoxemic respiratory failure (AHRF) supported by high-flow nasal oxygen. Prospective randomized physiologic crossover multicenter trial. Four ICUs in Marseille, France. Seventeen patients with laboratory-confirmed COVID-19 pneumonia and Pao /Fio less than or equal to 300 mm Hg while treated with high-flow nasal cannula oxygen therapy. Periods of APP and semirecumbent position (SRP) were randomly applied for 2 hours and separated by a 2-hour washout period. Arterial blood gases, end-tidal CO . and esophageal pressure were recorded prior to and at the end of each period. Inspiratory muscle effort was assessed by measuring the esophageal pressure swing (∆P ) and the simplified esophageal pressure-time product (sPTP ). The other endpoints included physiologic dead space to tidal volume ratio (V /V ) and the transpulmonary pressure swing. The APP increased the Pao /Fio from 84 Torr (61-137 Torr) to 208 Torr (114-226 Torr) ( = 0.0007) and decreased both the V /V and the respiratory rate from 0.54 (0.47-0.57) to 0.49 (0.45-0.53) ( = 0.012) and from 26 breaths/min (21-30 breaths/min) to 21 breaths/min (19-22 breaths/min), respectively ( = 0.002). These variables remained unchanged during the SRP. The ∆P and sPTP per breath were unaffected by the position. However, the APP reduced the sPTP per minute from 225 cm H O.s.m (176-332 cm H O.s.m ) to 174 cm H O.s.m (161-254 cm H O.s.m ) ( = 0.049). In spontaneously breathing patients with COVID-19-associated AHRF supported by high-flow nasal oxygen, the APP improves oxygenation and reduces the physiologic dead space, respiratory rate, and work of breathing per minute.