[Preserved spontaneous breathing during partial liquid ventilation. Results of experimental animal studies and their...

Controlled mechanical ventilation (CMV) may contribute to impaired hemodynamics in patients with respiratory failure. It is rational to assume that hybrid modalities of mechanical ventilation have fewer hemodynamic side-effects when spontaneous respiratory activity is allowed during the application of positive airway pressure. Partial liquid ventilation (PLV) has been shown to improve gas exchange in subjects with severe alveolar lung disease. We have shown that spontaneous respiratory efforts during proportional assist ventilation (PAV) is possible in experimental animals without lung disease whose lungs are partially filled with perfluorocarbons. In another series of experiments we demonstrated that PLV improves oxygenation and lung compliance in adult rabbits with severe surfactant deficiency, and in rabbits with meconium aspiration. In animals with meconium aspiration mortality, work of breathing and the degree of lung injury, as assessed by histological analysis, were reduced. In another two series of animals with and without surfactant deficiency spontaneous breathing supported by PAV was associated with increased cardiac output, stroke volume and oxygen transport, as compared to CMV after pharmacologically induced muscle paralysis. An increased arterial and venous pH in animals with surfactant deficiency during spontaneous breathing supported by PAV suggests improved tissue perfusion. Furthermore, gas exchange was improved during spontaneous breathing supported by PAV as compared to CMV and muscle paralysis.