[Acute respiratory failure: comparison of spontaneous ventilation with continuous positive airway pressure (CPAP) and mechanical ventilation with positive and expiratory pressure (CPPV) in 6 cases (author's transl)].

The hemodynamic and respiratory effects of spontaneous ventilation with continuous positive airway pressure (CPAP) and mechanical ventilation with positive and expiratory pressure (CPPV) were compared in six patients with acute respiratory failure. Arterial and mixed venous gases, cardiac output, oxygen delivery and consumption, airway and oesophageal pressures were measured, with each patient on intermittent positive pressure ventilation (IPPV), CPAP and CPPV with the same level of positive and expiratory pressure (PEEP = 20 cmH2O). CPAP was as efficient as CPPV for improving arterial oxygenation. Cardiac output was higher on CPAP than on CPPV due to a lower intra-thoracic pressure with spontaneous ventilation, thus oxygene transport was higher with this methode. However total oxygene consumption and PaCO2 were slightly increased with CPAP due to a higher breathing's work. So, CPAP is as efficient as CPPV at the same level of PEEP in improving intra-pulmonary shunt and PaO2, without adversely affecting cardiac output.