Time to desaturation less than one minute predicts the need for long-term home oxygen therapy

Exercise desaturation in patients with COPD is a pathophysiological phenomenon that is not wholly understood and whose clinical consequences are still unclear.

Eighty-three patients with moderate to severe COPD and P(aO(2)) > 60 mm Hg who desaturated during the 6-min walk test were followed for 5 years. Forty-eight patients had early desaturation (S(pO(2)) fell below 90% less than one minute after starting the walk test). Spirometry, blood-gas measurements, and 6-min walk tests were performed every 6 months. We recorded 6-min walk distance, baseline S(pO(2)), lowest S(pO(2)), and the time to S(pO(2)) < 90%. In each control, stable patients with severe hypoxia at rest who required long-term oxygen therapy were identified.

Upon completion of the study, 65% of the early desaturators had developed severe hypoxemia and required long-term home oxygen, versus 11% in the non-early desaturators (P < .001).

In patients with moderate to severe COPD, desaturation within the first minute of the 6-min walk test predicts the need for long-term home oxygen at 5-year follow-up.