The following is the summary of “Continuous Monitoring of Pulse Oximetry During the 6-Minute Walk Test Improves Clinical Outcomes Prediction in COPD” published in the January 2023 issue of Respiratory Care  by Batista, et al.

It was discovered by continuously measuring SpO2 during the 6 minute walk test (6MWT) that some patients with respiratory disorders may display values throughout the test lower than SpO2  reported at the end of the test. It is not yet known if this method enhances the accuracy of walk-induced desaturation detection in making prognoses of death and hospitalizations in COPD patients.421 patients (51% male) with mild-to-severe COPD did a 6MWT while their SpO2 was continuously monitored. Having a decrease in SpO2 ≥4% during exercise was considered desaturation. The rate of hospitalizations in the year following the 6MWT and the risk of death from any cause were measured.

In the middle of a mean (IQR) follow-up of 55.5 (30.264.1) months, 149 individuals (35.4% of the total) passed away. About 299 out of 421 samples (71%) showed signs of desaturation. End SpO2 was lower than average SpO2 during the test (88 [8,292]% vs. 90 [8,493]%) (P< .001). 81  out of 421 (19.2%) participants showed signs of desaturation during (but not after) the test. The presence of desaturation at the end of the test (1.85 [95% CI 1.02–3.36]) or only along the test (2.08 [95% CI 1.09–4.01]) remained significant predictors of mortality after adjusting for sex, body composition, FEV1, residual volume/total lung capacity ratio, walk distance, O2 supplementation during the test, and comorbidities in a multivariate Cox regression model. 

There was a correlation between presenting with any desaturation and a greater hospitalization rate than those who presented without exercise desaturation. Using logistic regression, researchers identified 2 independent predictors of desaturation during the test: walking interruption and diffusing capacity of the lung for carbon monoxide.  In adults with COPD, O2 desaturation was independently related to all-cause mortality and hospitalizations, despite being overlooked by end-exercise SpO2.


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