Sleep hypoventilation due to increased nocturnal oxygen flow in hypercapnic COPD patients.

Background and objective: Several COPD treatment guidelines recommend increasing oxygen flow during sleep to avoid nocturnal desaturation. However, such an increase could have deleterious clinical and gas exchange effects. The objective of this study was to evaluate short-term gas exchange alterations produced by increasing the nocturnal oxygen flow rate. Methods: Thirty-eight COPD patients with chronic hypercapnic respiratory failure were evaluated. In a cross-over study, patients were randomly assigned to receive the daytime oxygen flow rate on one night and an additional litre on the alternate night. Nocturnal pulse oximetry and arterial blood gases at awakening were measured, in each patient, on two consecutive days. Results: The administration of 1 L more oxygen during the night resulted in improved parameters of nocturnal oxygenation (oxygen pulse oximetry saturation-SpO(2); percentage of sleep time spent at SpO(2) < 90%-CT90; PaO2 at awakening). Nevertheless, such an increase in oxygen flow during the night was also associated with greater hypercapnia and acidosis (p < 0.05) the next morning. Conclusions: The increase of oxygen flow in severe COPD patients with established daytime hypercapnia improved nocturnal oxygenation but it also led to greater hypercapnia and respiratory acidosis at awakening in a considerable proportion of these patients.