Patients: Thirty-five patients with severe COPD were studied (Table 1). All subjects were former cigarette smokers with a clinical history consistent with COPD; patients were eligible for inclusion if they had a forced expiratory volume in 1 s (FEV1) less than 50% predicted and an FEV1 to forced vital capacity (FVC) ratio less than 65%. All patients were clinically stable and were studied while hospitalized at Mount Sinai Hospital, Cote St Luc, Quebec for a pulmonary rehabilitation program or for convalescence after a recent exacerbation of COPD. Patients admitted to the study were required to have a resting transcutaneous arterial oxygen saturation (SpO2) 85% or greater on room air. Those receiving supplemental oxygen needed to have that withheld for at least 2 h. Routine spirometry was performed, and FEV 1 and FVC recorded on the best of three expiratory efforts using an electronic spirometer (Vitalograph Model 42.000 Type C, Vitalograph Ltd, Buckingham, United Kingdom).
Table 1. Characteristics of patients with chronic obstructive pulmonary disease included in meal-induced oxygen desaturation and dyspnea study