Treatment results of 336 patients in critical state who had required prolonged (3-115 days) artificial pulmonary ventilation were analyzed. 3 groups were defined: 98 patients with complications after operations on thoracic and abdominal organs and organ failure development; 55 patients with surgical infection and sepsis; 183 patients with extensive burning injury III AB-IV degrees. Particular features of prolonged artificial pulmonary ventilation were studied. Optimum modes of respiratory therapy were determined. Frequency of complications was controlled.