Proportional assistierte Spontanatmung mit automatischer Tubuskompensation versus druckunterstützte Spontanatmung bei experimentell induziertem akuten Lungenversagen

It has been suggested, that the preservation of some degree of spontaneous breathing might be advantageous in acute respiratory distress. Therefore, proportional assisted ventilation with automatic tube compensation (PAV/ATC) and pressure support ventilation (PSV) were compared in an animal model of acute lung injury (ALI) regarding gas exchange, haemodynamics and ventilation-perfusion distribution. Using repetitive bronchoalveolar lavage manoeuvre, ALI was induced in 20 pigs until PaO2/FiO2 1h after the last lavage. After randomization, the pigs received for 8 hours either PAV/ATC (n=10) with 80% compensation for elastance and resistance and 100% tube compensation or PSV with a pressure support of 14-15cmH2O. Main results in terms of haemodynamics were a significant decrease of heart rate and cardiac output in the PSV group, Oxygenation improved in both groups significantly, associated with a reduction of intrapulmonary shunt in both groups. Thereby the ventilation-perfusion distribution was more inhomogeneous in the PAV group, instead of increased areas with physiologic VA/Q distribution, low-VA/Q areas were developed in this group. The fraction of dead space ventilation and the breathing rate increased in both groups significantly, while tidal volume decreased in both groups significantly. In this study, both forms of augmented spontaneous breathing showed positive effects on pulmonary gas exchange, whereas the improvement was more pronounced in the PSV group