Objective: To determine the nocturnal oximetry pattern in chronic obstructive pulmonary disease patients having no sleep apnea and presenting mild daytime hypoxemia, to identify probable daytime parameters capable of predicting nocturnal desaturation, and to evaluate the influence of nocturnal desaturation on the sleep pattern of these patients.
Methods: Twenty-five patients were divided into two groups: those with nocturnal desaturation and those without.
Results: Comparing the first group (52%) with the second, we found the following: age, 63 +/- 5 years versus 63 +/- 6 years; forced expiratory volume in the first second = 53 +/- 31% versus 56 +/- 19% predicted; ratio of forced expiratory volume in the first second to forced vital capacity, 49 +/- 14% versus 52 +/- 10%; arterial oxygen tension, 68 +/- 8 mmHg versus 72 + 68 mmHg; and arterial oxygen saturation, 93 +/- 2% versus 94 +/- 1%. Patients in the nocturnal desaturation group presented lower daytime arterial oxygen saturation and nocturnal arterial oxygen saturation by pulse oximetry. There was no difference between the two groups in terms of the sleep patterns observed. The ratio of forced expiratory volume in the first second to forced vital capacity was found to correlate with forced vital capacity, daytime arterial oxygen tension and daytime arterial oxygen saturation. In addition, arterial oxygen saturation by pulse oximetry during exercise was found to correlate with nocturnal arterial oxygen saturation by pulse oximetry. However, only daytime arterial oxygen saturation was predictive of nocturnal desaturation.
Conclusion: The only variable capable of predicting nocturnal desaturation was daytime arterial oxygen saturation. Nocturnal desaturation did not influence the sleep patterns of patients with chronic obstructive pulmonary disease accompanied by mild daytime hypoxemia.