Frequency of nocturnal hypoxia in clinically stable patients during stroke rehabilitation

Objective: Sleep disordered breathing is common in patients with cerebrovascular disease. Nocturnal hypoxia may lead to daytime tiredness and cognitive impairment, thus affecting progress. This study assessed the prevalence of nocturnal hypoxia during rehabilitation from stroke.

Design: Prospective observational trial.

Setting: The stroke rehabilitation wards of the North Staffordshire Hospital, UK and of Kreiskrankenhaus Grevenbroich, Germany.

Subjects: Adult patients on a stroke rehabilitation ward, 10 days to 3 months (mean 32 days, SD18) after stroke onset (n = 160). Age and local environment-matched controls (n = 156) without a history of stroke were recruited from the community at both centres.

Main measures: Pulse oximetry was performed overnight on the day of enrolment from 21:00 to 09:00. The baseline awake oxygen saturation, the mean nocturnal oxygen saturation, the lowest nocturnal oxygen saturation and the 4% Oxygen Desaturation Index were calculated for each participant.

Results: The mean baseline awake oxygen saturation of stroke patients was at 95.3% (SD 1.7), 0.5% lower than that of controls (P = 0.005, independent t-test). The group means of the mean nocturnal oxygen saturation for stroke patients were 0.5% lower (at 93.8% SD 2.2) than controls (P = 0.03, independent t-test). The mean lowest nocturnal oxygen saturation was at 79.4% (SD 9.9), 5.9% lower than that of the controls (P < 0.001, independent t-test). Considerably more stroke patients (n = 67, 42%) than controls (n = 24, 15%) had a parts per thousand yen10 desaturations below the baseline per hour (P < 0.001 chi-square test).

Conclusion: Clinically stable stroke patients enrolled in rehabilitation programmes have lower oxygen saturation and more nocturnal desaturations than non-stroke controls.