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