Anti-hypoxic potency of cerebroprotective drugs studied in a model of acute reversible respiratory failure.

The protective efficacy of pentoxiphylline, piracetam, and dihydroergotoxine against abrupt hypoxia was tested in a model of acute reversible respiratory failure, where repeated apnoeic attacks were induced by inhalation in repeated hypoxic exposures was reduced in control as well as in dihydroergotoxine-treated animals, it was increased after pentoxiphylline, and was not changed after piracetam. Repeated N2 inhalations reduced the duration of apnoea required for the development of mydriasis in all control cats. There were, however, no such reductions of the apnoeic interval in animals of the three groups treated with cerebroprotective drugs. The ratio between the total duration of hypoxia (hypoxic hyperventilation plus apnoea) and the time of recovery of breathing was significantly higher in the pentoxiphylline-treated animals already during the first hypoxic attack after drug application when compared both to the control and the dihydroergotoxine-treated animals. After piracetam the difference was apparent in the last hypoxic attack only. The model of acute reversible respiratory failure with apnoeic episodes induced repeatedly seems to be useful for testing some properties of cerebroprotective drugs during abrupt hypoxia.