Early Desaturation is a Predictor of Mortality in COPD

Abstract Background Oxygen desaturation during exercise is mainly observed in severe cases of chronic obstructive pulmonary disease (COPD) and is associated with a worse prognosis, but little is known about the type of desaturation that causes the greatest risk of mortality. Purpose of the research Does early desaturation produce higher mortality than other type of desaturation.? Basic procedures We studied all of the 6-minute walk tests performed periodically at a tertiary hospital over a period of 12 years in patients with moderate or severe COPD. We classified patients as non-desaturators if they did not suffer a drop in oxygen saturation (SpO2 <88%) during the test, early desaturators if the time until desaturation was <1 minute, and late desaturators if it was longer than 1 minute. The average length of follow-up per patient was 5.6 years. Main Findings Of the 319 patients analyzed, 126 non-desaturators, 91 non-early desaturators and 102 early desaturators were identified. The mortality analysis showed that early desaturators had a mortality of 73%, while it was 38% for non-early desaturators and 28% for non-desaturators, with a survival of 5.9 years compared to 7.5 years and 9.6 years, respectively (hazard ratio of 3.50; CI 95% 2.3-5.3; p <0.0001). Principal Conclusions The early desaturation seen in patients with chronic obstructive pulmonary disease is associated with greater mortality and is likely responsible for the poor prognosis shown globally in patients who desaturate. Patients with early desaturation have an almost 4-year shorter survival with respect to non-desaturators, and they thus require closer observation.