[Influence of ventilatory pattern on the functional situation of the lung during inhalation anaesthesia. Part I: Spontaneous breathing versus IPPB (author's transl)].

After five hours breathing spontaneously enflurane, halothane and methoxyflurane only the rabbits under enflurane showed, apart from a mild respiratory acidosis, no deterioration of pulmonary functional situation. Halothane and methoxyflurane exhibited under the same conditions a significant worsening of elastic behaviour of the lung. The structural bases of the mechanical impairment were atelectasis, dystelectasis and interstitial edema. Postnarcotic examination of lung extracts in the wilhelmy balance showed no abnormalities in the spontaneously breathing animals. If one compares these findings, indicating an irritation of surfactant by halothane and methoxyflurane with the results after IPPB the conclusion can be made that under these circumstances IPPB represents an additional stress for the alveolar lining layer. From the theoretical point of view therefore it would be advisable in patients with surfactant deficiencies to avoid the combination of halothane or methoxyflurane with IPPB. The use of PEEP will be discussed in part II. The value of periodical sighs could not be established under our conditions. Longer periods of spontaneous breathing seem only advisable under halothane but not under enflurane or methoxyflurane because their respiratory depressant properties.