Based on available data, it can be suggested that spontaneous breathing during ventilator support has not to be suppressed even in patients with severe pulmonary dysfunction if no contraindications are present. Experimental data do not support the contention that spontaneous breathing aggravates ventilator-induced lung injury. During spontaneous breathing increase in PTP is maximal in the depended lung areas in adjunct to the diaphragm and causes recruitment of initially atelectatic lung areas thereby avoiding cyclic alveolar collapse and reopening. This should result in a lung protective effect of adequate supported spontaneous breathing. Clinical data supported this belief demonstrating improvement in pulmonary gas exchange, systemic blood flow, and oxygen supply to the tissue and a decrease in days on ventilator support and duration of stay in the intensive care unit.