Hospitals that had less than fifty (50) central line-days per year in a given intensive care unit (ICU) are not required to report for that ICU. Similarly, hospitals and ambulatory surgery centers that performed less than twenty (20) procedures per year are not required to report for that surgical procedure. This is because infection rates based on too few central line-days or procedures would not be reliable or meaningful.  In addition, facilities that have at least 100 ventilator- days for all ICUs combined, are asked to voluntarily report the number of patients with their head-of-bed elevated to at least 30 degrees.