Table 3.

Comparison of ventilator-free days between the methylprednisolone plus cyclophosphamide and methylprednisolone alone groups

	Difference	95% CI*	P value
Unadjusted	−3.7	−5.9 - −1.6	0.0008
Instrumental variable analysis	2.2	−2.6 - 7.0	0.37
Instrumental variable analysis, patients with CT†	3.8	−1.1 - 8.7	0.13
Instrumental variable analysis, patients with CT, without furosemide	5.8	−5.2 - 16.8	0.30

*CI, confidence interval

†CT, computed tomography