[Respiratory and cardiac activity during sleep at high altitude (4650 m. above sea level)]

In this study, the relationship between the cardiac rhythm and ventilatory rhythm, during the sleep, at high altitude (4560 s.l.- Peruvian Andes) has been evaluated in native acclimated, and long-term resident people. The experimental observation has been performed from 11.00 p.m. to 7.00 a m. (when the barometric pressure was 430 mmHg, pO2 was 90 mmHg and paO2 was 71 mmHg) by using an eight channel polygraph for EEG, usefully modified for ECG and pneumographic recordings. In agreement with the observations of other Authors, a periodic breathing was recorded when the theta rhythm (low amplitude waves, characteristic of the second stage of the sleep) appeared in the EEG. During the REM stage of the sleep, the respiration becomes irregular, without periodicity in the ventilatory rhythm. Any statistical difference was not observed between European and Andinian subjects. During the N-REM phases of the sleep, the cardiac activity was often clearly dissociated from respiratory cycles. This finding suggests that, during the 2 and 4 phases of the sleep, in our experimental conditions, the cardio-inhibitory and cardio-acceleratory centers seem to lose the correlation with the regulatory centers of the breathing.