Interaction between low tidal volume ventilation strategy and severity of acute respiratory distress syndrome: a retrospective cohort study

Table 2 Crude outcomes and test of homogeneity in the traditional and low tidal volume subgroups

Variables	Subgroup with PaO₂/FiO₂ > 150			Subgroup with PaO_2/FiO₂ ≤ 150
Variables	Traditional tidal volume (n = 162)	Low tidal volume (n = 183)	p	Traditional tidal volume (n = 235)	Low tidal volume (n = 256)	p
Patients achieving unassisted breathing for 48 h [n (%)]	96 (59.2)	141 (77.0)	< 0.001	119 (50.6)	151 (58.9)	0.063
Death before discharge home and breathing without assistance [n (%)]	64 (39.5)	41 (22.4)	0.001	96 (40.8)	95 (37.1)	0.414
Risk ratio of death^#	0.56 (0.40–0.79)			0.91 (0.73–1.13)

^#The risk ratio was calculated using hierarchical chi-square analysis, and the p value for homogeneity (Mantel-Haenszel) was 0.0185

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