Continuous positive pressure through the nose can reverse chronic hypercapnia

: Sleep apnea syndrome is a clinical entity characterized by respiratory pauses during spontaneous sleep during which desaturation exists. A reduced group of patients suffering this pathology present chronic alveolar hypoventilation. The application of continuous positive pressure through the nose (CPAPn) is an effective therapeutic measure in the treatment of sleep apnea syndrome in its obstructive form. Its long term application normalizes, in some patients with chronic alveolar hypoventilation, daytime hypercapnia. We describe two patients presenting sleep apnea syndrome in whom the application of CPAPn reverted chronic hypercapnia after three and five months of treatment respectively. We agree with other authors that such normalization can be conditioned by a better performance of inspiratory musculature after the continuous application of CPAPn, which decreases the pressure which has to be generated by respiratory muscles in order to maintain inspiratory flux.