Evolution of nocturnal pulse-oximetry results in patients with chronic obstructive pulmonary disease

The aim of this study was to evaluate if results of overnight pulse-oximetry (PO) change with time and progression of the disease. We studied 39 COPD patients. Majority of them (33 pts) were treated with long-term oxygen therapy (LTOT). Fifty pairs of PO were performed in the whole group separated from 1 to more than 3 years. Pulmonary function tests were performed at the same time as PO. Results of these tests showed progressive deterioration in the lung function-decrease of FEV1 and PaO2. Despite of that there were no statistically significant changes in any variable of PO in any studied group. This phenomenon is difficult to explain. It may resulted from the improvement in the cardiac output observed in COPD patient undergoing LTOT. May be that studied groups were not large enough or time of observation was too short to reveal differences. Stabilization of PO results in spite of deterioration in the lung function in COPD patients needs more studies.