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