Summary

Abstract

Impairment of lung function is a constant feature of general anesthesia and the postanesthetic period. As the most conspicuous alterations a decrease of PaO₂, functional residual capacity, and pulmonary compliance as well as an increase of A-a DO₂, and closing volume deserve attention. These typical changes prompted us to investigate to what extent this is caused by the specific influence of fatsoluble inhalation anesthetics on the surfactant system of the lung. In addition, we were interested in ascertaining the significance of different ventilatory patterns — spontaneous breathing, intermittent positive pressure breathing (IPPB), and positive end-expiratory pressure ventilation (PEEP) — and whether the use of “parapulmonary” narcotics safeguards against possible changes. To clarifiy these questions, the different anesthetics and types of respiration currently in use were each tested in rabbits during 5-h anesthesias. The pulmonary compliance as determinded by a modified volume-pressure-diagram served as a suitable mean for evaluating surfactant activity “in situ”. Arterial blood gases provided additional information about resulting impairment of pulmonary gas exchange. After anesthesia the “in vitro” activity of the lining layer was measured with the Wilhelmy balance. Last but not least the histological picture of the lungs provided further information about resulting structural changes.