Exposures and outcomes

Awake, spontaneously breathing patients managed with noninvasive oxygen devices who were able to remain in the prone position for at least 2 h continuously were considered as patients in the awake prone group (main exposure); those not meeting this criterion, or in whom prone positioning was not attempted at all, were considered as the comparison group (awake supine). The primary outcome was successful orotracheal intubation for invasive mechanical ventilation and the secondary outcome was death during in-hospital follow-up. Factors associated with intubation among patients in the awake prone group were also evaluated.

The decisions to place patients in the prone position and perform orotracheal intubation were based on individualised medical criteria and were not priorly defined or standardised. Patients were managed with LFNC, HFNC or a nonrebreather mask; other noninvasive ventilation devices were either not used or unavailable across all centres.