Table 3.

Summary of the evidence for conscious prone positioning prior to the COVID-19 pandemic

Authors	n	Intervention (respiratory device)	Setting	Outcome	Key results	Strengths	Limitations
Scaravilli et al, 201533	15	Prone episodes, 1–3 per patient with duration 2–4 hours (longest 8 hours) Oxygen facemasks, CPAP and HFNC)	ICU (ARDS)	Change in PaO2/FiO2 from supine to prone position, then return to supine	PaO2/FiO2 (kPa) 11.9±3.7 to 16.5±7.1* (returning to 12.1±5.6)*	Measured response to re-supination after 6–8 hours	Respiratory device the same over prone episode in only 18/43
Ding et al, 202034	20	Protocolised trials of HFNC or CPAP/BiPAP +/− prone positioning	ICU (ARDS)	Intubation rate Change in PaO2/FiO2 from supine to prone position	55% intubated (expected 75%) PaO2/FiO2 (kPa) 12.7±2.9 to 17.3±4.7 kPa† (those who avoided intubation)	Meaningful primary outcome Suggests benefit in moderate ARDS or varying aetiology	Complex protocol with combination of interventions unachievable on wards Results for success and failure groups reported separately
Valter et al, 200335	4	Single episode of prone positioning, duration 50 minutes to 5 hours (CPAP/BiPAP used pre-prone positioning in n=3)	ICU (ARF)	Change in PaO2/FiO2 from supine to prone position	PaO2/FiO2 (kPa) 11.9 to 24.7 (mean values)		Small case series
Bellone and Basile, 201836	3	Repeated episodes of prone positioning for 6 hrs/day (HFNC during prone positioning)	Emergency ward (ARF)	Change in PaO2/FiO2 from supine to prone position	PaO2/FiO2 (kPa) 15.7 to 36.7 (1 day of intervention) to 40.4 (9 days of intervention	Suggests improvement with sustained use of prone positioning	Small case series

ARF = acute respiratory failure; BiPAP = bilevel positive airway pressure; CPAP = continuous positive airway pressure; ED = emergency department; HFNC = high flow nasal cannula; ICU = intensive care unit. ^*p<0.05 from preceding intervention. ^†p=0.016, HFNC to HFNC + prone.