Table 1.

Interpretation of OFDs

Severity	OFDs (d)	Interpretation
More severe	–1	Patient died before the end of day 28.
	0	Patient survived through day 28 and received oxygen on days 1 and 28.
	1	Patient survived through day 28 and was free of oxygen use for 1 d in the first 28 d after randomization.
	10	Patient survived through day 28 and was free of oxygen use for 10 d in the first 28 d after randomization.
	25	Patient survived through day 28 and was free of oxygen use for 25 d in the first 28 d after randomization.
Less severe	28	Patient survived through day 28 and was free of oxygen use on every calendar day from days 1 to 28.

OFD = oxygen-free day.