Nocturnal Oxygen Saturation and Sleep Quality in Long-Term Survivors of Thoracoplasty

Abstract

The extent and the predictors of nocturnal hypoxemia were studied in 9 men and 11 women treated for pulmonary tuberculosis by thoracoplasty 30-54 years previously. The patients had a scoliotic (Cobb) angle of 4-53 degrees. Median values for pulmonary function were: forced expiratory volume in 1 s 1.2 liters (49% of the predicted value), vital capacity 1.9 liters (54%), total lung capacity 3.6 liters (62%), and supine waking partial pressure for arterial oxygen 9.7 kPa. Four patients were hypercapnic. The patients' mean nocturnal SaO2 ranged from 83 to 94% (median 91.8%), and the SaO2 level below which the patients spent 10% of the total nocturnal recording time ranged from 78 to 92% (median 89.4%). A multiple stepwise linear regression analysis identified supine waking SaO2 as a significant predictor of nocturnal O2 desaturation, accounting for about 80% of the variability in nocturnal SaO2 levels; lung function values and Cobb angle were not significant independent predictors. The sleep quality, assessed by EEG, was good. It is concluded that in thoracoplasty patients with mild hypoxemia during wakefulness, the degree of sleep-related oxygen desaturation was modest and closely related to the waking level of SaO2.