[Immediate effects and conditions of effectiveness of a session of mechanical assisted ventilation (M.A.V.) in severe respiratory insufficiency (PaCO2 greater than 50 mmHg) out of intensive care conditions (author's transl)].

Effectiveness and haemodynamic tolerance of M.A.V. in conscious patients with a severe respiratory insufficiency is mainly due to the proper adaptation to ventilator with low frequency and adequate V.T. Thus M.A.V. is an eventual complement to directed ventilation exercises which in addition reduce the "rebound" of hypoxia and hypercapnia after a M.A.V. session. A proper adaptation ensures haemodynamic tolerance. Expiratory time should be sufficient in such obstructive patients. A post inspiratory pause can improve V.C.O2. Nevertheless, it should not shorten inspiratory time to less than one second and for each patient the best ventilatory profile should be properly established taking into account blood gases, circulatory, expired CO2 and clinical monitoring.