Trial of BiPAP during Sleep in Chronic Respiratory Failure with hypercapnic

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Purpose : Some patients with chronic respiratory failure, especially patients with hypercapnia, show severe nocturnal oxygen desaturation. The oxygen desaturation during sleep aggravate the general condition of the patients. The main reason of the oxygen desaturation is believed to be the hypoventilation during sleep. Meanwhile, pressure support ventilator has been ameliorated and bilevel positive airway pressure (BiPAP) system, by which we can expect better tolerance, has become available. We, therefore, tried to elucidate the pathophysiology of nocturnal oxygen desaturation, way of setting of BiPAP and optimal setting of pressures for BiPAP,in order to apply BiPAP properly for patients of chronic respiratory failure with nocturnal oxygen desaturation.Methods : We measured oxygen desaturation during sleep using pulse oxymeter and recorded continuously using a notebook computer in 40 patients with chronic respiatory failure. In 20 patients, measurements were repeated for more than a mo … More nth and the results were compared with the various parameters showing general conditions. Some of the patients showing nocturnal hypoxia were examined using polysomnograph and capnograph in addition to pulse oxymeter. Relations of the sleep stage to the nocturnal oxygen desaturation, ventilation, or end-tidal CO2 were analyzed. BiPAP was applied during sleep to some of the patients with nocturnal oxygen desaturation.Results : Many patients of chronic respiratory failure with daytime PaO2 over 60 torr showed nocturnal oxygen desaturation and some of them were very severe desaturation. Most of the patients showing severe nocturnal desaturation had history of repeated admission for acute exacerbation. Nocturnal oxygen desaturation was worse in REM stage than in non-Rem stage. BiPAP satisfactory prevented nocturnal oxygen desaturation even in REM stage. Repeated trials were necessary to obtain optimal pressures for BiPAP.Conclusion : Prevention of nocturnal oxygen desaturation is important for the patients of chronic respiratory failure and BiPAP satisfactory prevents the nocturnal oxygen desaturation. Less