[Sleep hypoxemia during CPAP treatment in patients with obstructive sleep apnoea syndrome with chronic hypercapnia].

UNLABELLED: The aim of the study was to find the clinical features of the hypercapnic OSA patients, indicating possible failure of CPAP treatment in preventing sleep hypoxemia. The material of the study consisted of 37 hypercapnic OSA patients (age 49 +/- 9 years, apnea index 50 +/- 15, daytime PaCO2 52 +/- 6 mm Hg). In 1 patient arterial oxygen desaturation persisted because of the replacement of all mixed apnoeas by central apnoeas. In 26 patients SaO2 during CPAP treatment (85 +/- 27% in NREM and 72 +/- 12% in REM sleep) was lower during sleep than baseline SaO2 (91 +/- 2%, p < 0.05), in spite of disappearance of sleep apnoeas. In this group of patients there was more profound desaturation during sleep apnoeas (mean low SaO2 in NREM sleep 69 +/- 11% vs 84 +/- 4% and in REM sleep 50 +/- 8% vs 71 +/- 3% p < 0.001) and longer maximal apnea duration in NREM sleep (85 +/- 36s vs 56 +/- 23s, p < 0.01); in 24 of these patients there were the episodes of desaturation (mean SaO2 72 +/- 13%) during sleep lasting 2-6 min (mean 4 +/- 2 min) and in 16 patients (67%) there was secondary erythrocytosis.

CONCLUSION

Hypoxemia during sleep in spite of disappearance of sleep apneas may occur in some hypercapnic, extremely obese OSA patients with ventilatory insufficiency, secondary erythrocytosis, profound arterial oxygen desaturation during sleep apnoeas and extremely long apnoeas during NREM sleep and with the signs of coexisting sleep hypoventilation syndrome.