Brief Report - Predictors of Nocturnal Oxygen Desaturation in Chronic Obstructive Pulmonary Disease in a South Indian Population

Context: Nocturnal Oxygen Desaturation (NOD) in patients with chronic obstructive pulmonary disease (COPD) is associated with a poor prognosis. Aims: To document the occurrence of NOD in COPD and to identify factors which might predict NOD in COPD patients with daytime arterial oxygen tension (PaO₂) ³60 mm Hg. Settings and Design: This prospective study was conducted in patients attending the special respiratory clinics or admitted in JIPMER, Pondicherry. Methods and Material: Thirty consecutive patients with COPD were divided into two groups, desaturators and non-desaturators on the basis of nocturnal oxygen saturation. Statistical analysis used: Unpaired 't' test, Karl Pearson's correlation equation and stepwise multiple regression analysis was done. Results: Fourteen patients (46.6%) experienced NOD. Desaturators had lower awake oxygen saturation, PaO₂, forced vital capacity, forced expiratory volume in one second and peak expiratory flow rate. There was positive correlation between nocturnal O₂ saturation and PaO₂ (r=0.638 and P value =0.014) and awake SPO₂ (r=0.901 and P value >0.001). Conclusions: The rate of occurrence of NOD in COPD was 46.6%. Awake SPO₂ is the only single predictor of nocturnal oxygen desaturation in these patients.

Keywords
Nocturnal oxygen desaturation, chronic bronchitis, emphysema, predictors