Chemical control of ventilation and sleep arterial oxygen desaturation in patients with COPD

In 41 patients with hypoxemic COPD, nocturnal changes in arterial O2 saturation were compared with measurements of hypoxic and hypercapnic ventilatory control, which were carried out during wakefulness. In 24 patients, sleep was judged visually, whereas in 17, sleep was staged by electroencephalogram (EEG). There were no differences between the 2 groups in terms of lung function, blood gases, or sleep desaturation. All patients desaturated during sleep, with maximal desaturation occurring during rapid eye movement (REM) sleep. The maximal nocturnal change in O2 saturation observed in each patient was negatively correlated with the patient's ventilatory sensitivity to hypercapnia; this relationship was independent of sleep stage. Both maximal and mean nocturnal changes in O2 saturation were negatively correlated with O2 saturation during wakefulness. Hypoxic ventilatory response was not related to nocturnal desaturation. Patients who are sensitive to hypercapnia are unlikely to show major sleep desaturation, whereas those who are insensitive to CO2 may do so, particularly if they have low O2 saturations while awake.