A therapist-driven protocol, which was modeled after the available comparative studies of wean modalities, was implemented to optimize the time required to achieve wean weaning.4–6,8 The respiratory therapists who were in charge of the weaning protocol were blinded to the Cst and RSBI, which were separately obtained by the investigators. In each case, an attempt was made to identify and address the impediments to weaning in weekly multidisciplinary meetings that included a nutritionist, respiratory therapist, speech pathologist, physical therapist, social worker, pharmacist, physician (LSA), unit manager, and members of the nursing staff. Impediments to weaning were included only in as much as they were deemed to contribute to the respiratory failure, and were classified as neurologic (including central, spinal, or neuromuscular causes), cardiac (including coronary artery disease and congestive heart failure), infectious (any cause including pneumonia), or pulmonary (including COPD, asthma/bronchitis, obesity hypoventilation, ARDS, and interstitial lung disease). Patients were placed on assist-control ventilation on arrival in the PCU and were considered ready for a weaning trial if systolic BP was between 90 and 180 mm Hg, heart rate was between 50 and 130 beats/min, temperature was < 101°F (< 38.3°C), and minute ventilation was < 15 L/min. On each of the first 2 days following admission to the PCU, patients who considered to be ready for weaning underwent spontaneous breathing trials, and a successful trial was followed by use of a tracheostomy mask with oxygen supplementation to maintain a pulse oximetry saturation of ≥ 94%. Those failing the spontaneous breathing trials on the first 2 days were rested using assist-control ventilation for the remainder of the day and spent subsequent days receiving pressure support ventilation at a level sufficient to maintain a respiratory rate of < 30 breaths/min. For patients who tolerated the trials, pressure support was decreased by 2 cm H2O at least twice daily. The tolerance of pressure support at 5 cm H2O for at least 2 h was followed by use of a tracheostomy mask. Patients undergoing a spontaneous breathing trial or a pressure support trial were returned to therapy with assist-control ventilation if they had a respiratory rate of > 30 breaths/min, and an increase in heart rate by 20 beats/min, a decrease in systolic BP by ≥ 20 mm Hg, or a decrease in oxygen saturation by ≥ 5%. The TTW was calculated as the number of days from admission to the PCU to the first day of the last successful 48-h weaning trial regardless of ultimate outcome.