[Paradoxical respiratory response, changes in heart rate and skin circulation in progressive isocapnic hypoxia in sleep apnea patients].

In 73 patients with sleep apnea syndrome, lung function tests, night-time polysomnography for determining the apnea index (AI), hyperoxic progressive hypercapnia tests under rebreathing conditions, and, after a short pause, isocapnic progressive hypoxia tests were carried out. The objective of these examinations was to study peripheral and central chemosensitivity, changes in heart rate and capillary cutaneous circulation under isocapnic hypoxia in patients with sleep apnea syndrome (SAS). The following linear relationships were presupposed for the evaluation: for peripheral chemosensitivity between SaO2 decrease and the increase in respiratory minute volume (VE) and for central chemosensitivity between PETCO2 rise and VE increase. Of the SAS patients with an AI > or = 10, 22.5% did not react to the hypoxia test with and increase in VE but rather with a decrease in the respiratory minute volume. This patient group exhibited a positive correlation between an increase in capillary cutaneous circulation and an increase in heart rate during the hypoxia test. The hypoxic respiratory response behavior is independent of the hypercapnic respiratory response, age, Broca index, initial heart rate, blood pressure, pulmonary function values, and the size of the apnea index. The results are discussed in the context of a reduced peripheral chemosensitivity and an associated reduced sympathetic activation.