[Problems in prolonged artificial respiration. A review].

For about twenty years, the method for prolonged artificial respiration was an imitation of spontaneous breathing pattern. New pathophysiological informations about acute respiratory failure showed that a technique which is widely different in frequency, cycle, and tidal volume is more suitable for the fast and safe restauration of spontaneous breathing. Especially the determination of pulmonary shunt flow (QS/Qt), and of the ratio of dead space to tidal volume (VD/VT) have completed our knowledge. In the management of patients with prolonged artificial ventilation, the calculation of shunt flow allows an evaluation of therapeutic procedures. This was the reason to present a nomogram, which simplifies the determination of pulmonary shunt and to discuss an easy, non-invasive method to at least estimate its amount.