<qa>  What is the goal of the retrospective cohort study?This will be a retrospective cohort study that is performed between two medical intensive care units ICU. The goal is to compare outcomes of patients that have received care in medical intensive care units in a tertiary care facility with two different models; the traditional model including a resident, pulmonary fellow and attending and a nontraditional model which has Nurse Practitioners as the direct care deliverer, a pulmonary fellow, and an attending. Outcomes that will be measured include ICU length of stay, hospital length of stay after ICU discharge, ventilator days, daily spontaneous breathing trials, and daily awakening trials, as well as mortality in hospital and after discharge. 