Awake prone positioning (APP) has been proven to reduce the intubation rate for patients with COVID-19-induced hypoxemic respiratory failure. Our recent meta-analysis found APP was only effective for patients who were treated by high-flow nasal cannula (HFNC), not for patients using conventional oxygen therapy (COT).In a recent multicenter RCT, Perkins and colleagues reported that continuous positive airway pressure (CPAP) was superior to HFNC and conventional oxygen therapy in reducing intubation rate. Thus, it is essential to evaluate the physiological mechanism of APP under different respiratory supports, such as COT, HFNC, or CPAP.
Awake prone positioning (APP) has been proven to reduce the intubation rate for patients with COVID-19-induced hypoxemic respiratory failure. Our recent meta-analysis found APP was only effective for patients who were treated by high-flow nasal cannula (HFNC), not for patients using conventional oxygen therapy (COT).In a recent multicenter RCT, Perkins and colleagues reported that continuous positive airway pressure (CPAP) was superior to HFNC and conventional oxygen therapy in reducing intubation rate. Thus, it is essential to evaluate the physiological mechanism of APP under different respiratory supports, such as COT, HFNC, or CPAP.~We hypothesize that HFNC or CPAP is more effective when combined with APP than COT combined with APP. Electrical impedance tomography (EIT imaging) has been broadly utilized to assess patient ventilation homogeneity and respiratory volume monitor (RVM) has been used to evaluate patient's tidal volumes breath-by-breath. In this study, 20 healthy volunteers will use different respiratory support devices (HFNC, CPAP, and COT) in different settings and their combinations withAPP in a random sequence, assessed by EIT and RVM.