Oxygen desaturation during sleep as a function of the underlying respiratory disease.

Patients with hypoxemia due to respiratory diseases may desaturate further during sleep. A quantitative analysis of this sleep-induced desaturation, simultaneously comparing patients with different respiratory diseases, could identify patient groups especially prone to develop nocturnal hypoxemia. I have therefore compared the changes in oxygenation during sleep in three groups of patients with the same baseline oxygen saturation but with entirely different types of respiratory dysfunction, namely interstitial lung disease (n = 14), chronic obstructive pulmonary disease (n = 29), and scoliosis (n = 10). The patients with scoliosis had considerably larger sleep-induced desaturation than the patients with lung diseases. Their oxygen saturation was also more unstable than that of the others during REM sleep; possibly a consequence of their lower position on the oxyhemoglobin dissociation curve during this sleep stage. The results suggest that sleep studies may be more informative in patients with scoliosis, for example, where a need for nocturnal-assisted ventilation can be revealed, than in patients with lung diseases.