Table 1.

Subgroups of Data Available

Variables	Patients, Total No.	Sites Providing Data
Dates of ICU admission	12,213	16
Met age criteria	11,536	16
ICU admissions, No.	5,385	8
Non-ALI diagnosis	8,225	16
Lack of arterial blood gas measurements	1,457	16
Fio2	1,052	15
Spo2	904	15
PEEP	840	12

Centers were required to report primary but not all exclusion criteria for the prone-position study. As such, this table displays the total number of patients for which the variables of interest were available and how many centers provided this information.