Table 1.

Characteristics of the studies included in the analysis

Study	Guervilly et al. [6]	Garcia et al. [5]	Rilinger et al. [7]	Giani et al. [3]	Petit et al. [4]
Design	Monocentric retrospective cohort study	Monocentric retrospective cohort study	Monocentric retrospective cohort study	Multicentric retrospective cohort study	Monocentric retrospective cohort study
Country	France	France	Germany	Italy	France
Case volume# of the ECMO centers, runs/year (V-V runs)	55 (50)	45 (25)	125 (35)	35–55 (25–33)&	450 (60)
Total number of patients (Prone group)	168 (91)	25 (14)	158 (38)	240 (107)	298 (64)
Population	ARDS patients on	COVID-19 ARDS patients on V-V ECMO	ARDS patients on V-V ECMO	ARDS patients on V-V ECMO	ARDS patients on V-V ECMO
Prone positioning duration	16 (12–16) hours	16 (15–17) hours	20 (17–21) hours	15 (12–18) hours	16 (16–16) hours
Statistics	Univariable analysis, individual matching	Univariable analysis	Multivariable analysis, propensity score matching	Multivariable analysis, propensity score matching	Propensity score matching
Outcome
Last follow-up	90 days	28 days	Hospital discharge	Hospital discharge	90 days
Mortality, Prone vs Supine group	36% vs 58%*	79% vs 27%°	63% vs 63%*	30% vs 53%*	25% vs 46%*

^&Annual case volume before the COVID-19 pandemic

^%Case volume range of the centers participating to the multicentric study

^*Mortality rates of matched patient cohorts

°Unadjusted mortality