Table 2.

Prognostic factors associated with mortality

	uOR analysis			aOR analysis			aHR analysis			Mean difference analysis			GRADE certainty
	Studies, n	Patients, n	uOR (95% CI)	Studies, n	Patients, n	aOR (95% CI)	Studies, n	Patients, n	aHR (95% CI)	Studies, n	Patients, n	Mean difference (95% CI)
Patient factors
Older age	1145, 48, 49, 52, 56, 61, 62, 68, 69, 71, 72	6275	2·51 (2·07 to 3·03)	443, 44, 67, 68	1137	2·09 (1·22 to 3·59)	513, 38, 45, 70, 71	5607	2·27 (1·63 to 3·16)	..	..	..	High
Male sex	266, 37, 39, 40, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 58, 60, 62, 63, 64, 65, 66, 67, 68, 71, 74	7947	1·34 (1·20 to 1·49)	442, 43, 44, 67	887	1·42 (0·98 to 2·05)	413, 44, 71, 75	5669	1·06 (0·96 to 1·16)	..	..	..	Moderate
Chronic lung disease	1935, 37, 39, 40, 46, 49, 50, 52, 55, 60, 62, 64, 66, 67, 68, 71, 72, 73, 74	9387	1·08 (0·92 to 1·26)	335, 43, 44	431	2·50 (1·09 to 5·74)	313, 35, 71	5103	1·55 (1·20 to 2·00)	..	..	..	Moderate
Obesity	1435, 41, 49, 51, 54, 55, 61, 62, 66, 67, 68, 72, 73, 74	5408	0·84 (0·72 to 0·97)	243, 44	330	0·67 (0·36 to 1·27)	271, 74	275	0·94 (0·75 to 1·19)	..	..	..	Low
Immunocompromised	535, 46, 50, 68, 71	666	2·34 (1·19 to 4·61)	173	1985	4·35 (2·46 to 7·69)	113	4812	1·06 (0·83 to 1·35)	..	..	..	Low
Pre-cannulation disease factors
Higher driving pressure	..	..	..	..	..	..	238, 74	244	2·36 (1·40 to 3·97)	..	..	..	High
Longer symptom duration	..	..	..	..	..	..	..	..	..	837, 42, 56, 58, 63, 65, 69, 71	463	−1·51 days (−2·65 to −0·36)	Moderate
Higher PaCO2	..	..	..	..	..	..	238, 74	244	3·18 (1·41 to 7·15)	1635, 37, 40, 41, 43, 46, 49, 51, 53, 54, 58, 60, 64, 71, 72, 74	1929	−4·04 mm Hg (−6·44 to −1·64)	Moderate
Longer IMV duration	635, 36, 45, 57, 59, 72	1482	1·94 (1·40 to 2·67)	343, 67, 73	455	1·11 (0·65 to 1·92)	145	127	1·66 (1·00 to 2·75)	2037, 38, 40, 41, 42, 43, 46, 53, 54, 56, 58, 60, 63, 64, 65, 69, 71, 72, 73, 74	3897	−1·15 days (−1·85 to −0·46)	Moderate
Lower PaO2/FiO2 ratio	..	..	..	..	..	..	238, 71	349	1·28 (1·12 to 1·46)	2035, 37, 38, 41, 43, 49, 51, 53, 54, 55, 58, 60, 63, 64, 65, 69, 71, 72, 73, 74	4189	1·52 (−1·16 to 4·20)	Low
Higher plateau pressure	..	..	..	..	..	..	..	..	..	1235, 38, 40, 41, 43, 49, 54, 58, 65, 71, 72, 74	1738	−0·71 cm H2O (−1·15 to −0·06)	Low
Need for renal replacement therapy	749, 51, 54, 60, 65, 71, 72	1145	3·18 (1·41 to 7·17)	..	..	..	..	..	..	..	..	..	Low
Lower positive end expiratory pressure	..	..	..	..	..	..	..	..	..	1637, 40, 46, 49, 51, 54, 58, 60, 63, 64, 65, 68, 71, 72, 73, 74	3750	−0·05 cm H2O (−0·37 to 0·26)	No effect (low)
Higher tidal volume	..	..	..	..	..	..	..	..	..	935, 38, 40, 41, 53, 54, 71, 72, 74	1304	0·03 mL/kg (−0·09 to 0·15)	No effect (low)
Lower compliance	..	..	..	..	..	..	..	..	..	1038, 41, 43, 53, 54, 60, 63, 65, 71, 74	1149	1·55 (−0·12 to 3·21)	Very low
Higher peak pressure	..	..	..	..	..	..	..	..	..	537, 49, 51, 64, 73	2235	1·20 (−1·51 to 3·90) cm H2O	Very low
Bacterial co-infection	..	..	..	240, 73	2059	0·58 (0·13 to 2·57)	213, 70	5131	1·03 (0·88 to 1·20)	..	..	..	Moderate
Pre-ECMO proning	..	..	..	267, 73	2490	0·97 (0·58 to 1·63)	244, 75	667	1·18 (0·86 to 1·61)	..	..	..	Low
Centre factors
Lower volume	..	..	..	243, 68	609	2·27 (1·28 to 4·05)	313, 70, 75	5526	1·57 (1·11 to 2·20)	..	..	..	Moderate

uOR=unadjusted odds ratio. aOR=adjusted odds ratio. aHR=adjusted hazard ratio. GRADE=Grading of Recommendations Assessment, Development and Evaluation. PaCO₂=partial pressure of arterial carbon dioxide. IMV=invasive mechanical ventilation. PaO₂=partial pressure of arterial oxygen. FiO₂=fractional concentration of oxygen in inspired air. ECMO=extracorporeal membrane oxygenation.