Fig. 3. Average daily workload by hours of the day. During each hour of the workday between 6:00 AM and 11:00 PM, the average numbers of staff required (providers, anesthesiologists, and break personnel) were determined. Operating rooms (green line ) equals the number of providers, and critical portions (red line ) are as defined in tables 1and 2, indicating the number of supervising anesthesiologists required. Breaks (purple line ) represent staff relieving providers for lunch and bathroom breaks. The total number of providers needed (blue line ) is the sum of the other three quantities. The peak activity occurred at 7:30 AM, as did the number of critical portions of cases. Some operating rooms have scheduled start times of 6:30 AM and others at 7:30 AM, based on surgical specialty; this has no bearing on the results.