Table 1.

Studies on the use of CPAP/non-invasive ventilation in Covid-19-related pneumonia. Legenda: n. of pts: number of patients; DNI: Do Not Intubate; hCPAP. Helmet CPAP; NPPV: non-invasive postitive pressure ventilation; HFNC: high flow nasal cannulae; NRB: non rebreathing mask; RR: respiratory rate; SpO2: Oxygen pulse saturation; PaO2: arterial Oxygen partial pressure; AHRF: acute hypoxemic respiratory failure; PaO2/FiO2: the ratio between arterial oxygen partial pressure and fractional concentration of inspired oxygen; CXR: Chest radiography; CRP: C-reactive Protein. NR: not reported.

Study	Design	n. of pts	Technique	Failure%	Starting crit.	Failure pred.
Duca et al.	Retrospective	85	hCPAP (71); NPPV (7); IMV (7)	88,5% Deaths: 76.5%	PaO2< 60, RR>30 in NRB mask	age > 60
Alviset et al.	Retrospective	49	Mask CPAP	53% Deaths: 36%	SpO < 90% in NRB mask	Low basal PaO2
Di Domenico et. Al.	Retrospective	90 (27 DNI)	CPAP/NPPV	57% Deaths: 47% 89% in DNI	SpO2 < 90% or < 94% on O2 12- 15 l/min	Low basal PaO2/FiO2 ratio
Franco et al.	Prospective	670	163 HFNC, 330 hCPAP, 177 NPPV	30% Deaths: 30%	SpO2 < 94% RR > 20 poor response to O2 15 L/min	Age, n. of comorbidities, Low PaO2/FiO2
Nightingale et al.	Retrospective	24	Mask CPAP	38%	Type 1 AHRF	Age, n. of comorbidities
Burns et al.	Retrospective	28 (DNI)	Mask CPAP (23) NPPV (5)	Deaths: 50%	SpO2 < 94% In O2 40%	«Typical» aspect on CXR
Bellani et al	Prospective	909	CPAP 85% (mainly via helmet), NPPV 10%; HFNC 5%	37,6%	n.r.	Lower PaO2/FiO2 ratio; higher CRP; platelet count