Survival among all patients by duration of ventilation and tracheostomy status. Kaplan-Meier plot demonstrating one-year survival by PMV status. The group with the best survival is those who were ventilated for < 21 days and who received a tracheostomy. Persons ventilated for at least 21 days but who did not receive a tracheostomy experienced the worst survival. Other groups had intermediate one-year survival. MV, mechanical ventilation; PMV, prolonged mechanical ventilation.