The clinical impact of nocturnal desaturation on health-related quality of life (HRQL) and sleep in COPD has been little studied. We aimed to evaluate the prevalence and clinical impact of nocturnal desaturation in a typical outpatient population with COPD.
Between 2002 and 2005, consecutive patients with COPD attending outpatient services at the study centre underwent resting oximetry, if they were not on domiciliary oxygen therapy. If their resting saturations were less than 95%, overnight pulse oximetry was performed. Significant nocturnal desaturation was defined as spending more than 30% of at least one of two nights with a saturation of less than 90%. The Chronic Respiratory Questionnaire (CRQ) and SF-36 were used to assess HRQL, and the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Score (ESS) and Functional Outcomes of Sleep (FOSQ) questionnaires were used to assess sleep quality and daytime function.
Of 1104 patients, 803 underwent resting oximetry and 79 had resting oxygen saturations of less than 95%. Of these, 59 agreed to undergo overnight oximetry (mean age 70.5 years, FEV1 37.2% predicted, resting pO2 on air 8.9 kPa). Significant nocturnal desaturation was seen in 29 (49.2%) of the 59 subjects. The prevalence of nocturnal desaturation in the whole clinic population could therefore be estimated at 4.8%. There were no significant differences in CRQ, SF-36, PSQI, ESS or FOSQ scores for desaturators when compared with non-desaturators.
Significant nocturnal desaturation was common in COPD patients with resting saturations of less than 95%, but was estimated to have a prevalence of less than 5% in the whole outpatient population. Nocturnal desaturation was not associated with impairment of HRQL, sleep quality or daytime function.