Table 3 Adjusted associations between subgroups and hospital mortality

PaCO₂ groups

 Hypocapnia vs. normocapnia

1.39 (1.18–1.63)^a

<0.001

 Hypercapnia vs. normocapnia

1.10 (0.95–1.27)^a

0.20

 Hypercapnia vs. hypocapnia

0.79 (0.67–0.94)^a

<0.01

PaO₂ groups

 Hypoxia vs. normoxia

1.34 (1.08–1.66)^b

<0.01

 Hyperoxia vs. normoxia

1.13 (0.81–1.57)^b

0.46

 Hyperoxia vs. hypoxia

0.85 (0.58–1.24)^b

0.39

Alternative PaO₂ categories^c

 55-80 vs. >300 mmHg

1.06 (0.76–1.50)^b

0.72

 80-102 vs. >300 mmHg

0.90 (0.64–1.27)^b

0.55

 102-300 vs. >300 mmHg

0.79 (0.56–1.11)^b

0.17