Table 2.

Patient and ICU Characteristics.^*

Characteristic	Control Schedule	Intervention Schedule
Patients — no.	3,267	3,310
ICU admissions — no.	3,508	3,591
Patient-days — no.	18,749	20,072
Age — yr	7.3±6.7	7.1±6.6
Male sex — no./total no. (%)	1853/3508 (52.8)	1943/3591 (54.1)
Median length of stay (IQR) — days	2 (2–5)	2 (2–5)
Median chronic condition indicator (IQR)†	2 (1–4)	2 (1–4)
ICU patients per resident physician — no.‡	6.7±2.2	8.8±2.8

^*Plus–minus values are means ±SD. The control schedule included shifts of 24 hours or more. The intervention schedule eliminated extended shifts and cycled resident physicians through day and night shifts of 16 hours or less. ICU denotes intensive care unit, and IQR interquartile range.

^†The chronic condition indicator is a marker of a patient’s coexisting conditions, derived from administrative billing codes. Higher numbers indicate the presence of more coded chronic conditions.³⁵

^‡The number of ICU patients per resident physician is calculated as the average census of patients at each site during each schedule divided by the average number of resident physicians present at each site during each schedule.