DISTANCE AND OXYGEN DESATURATION DURING SIX-MINUTE WALK TEST AS PREDICTORS OF LONG-TERM MORTALITY IN PATIENTS WITH COPD.
Chest. 2008 Jul 14;
Authors: Casanova C, Cote C, Marin JM, Pinto-Plata V, de Torres JP, Aguirre-Jaíme A, Vassaux C, Celli BR
Rationale The distance walked in the 6-minute walk test (6MWT) predicts mortality in patients with severe COPD. Little is known about its prognostic value in patients with a wider range of COPD severity, living in different countries and the potential additional impact of oxygen desaturation measured during the test. Methods We enrolled 576 stable COPD outpatients in Spain and the United States of America, and followed them for at least three years (median 60 months). We measured FEV(1), BMI, PaO(2), the Charlson co-morbidity score and distance walked (6MWD) and O(2) saturation (SpO(2)) during the 6MWT. Desaturation was defined as a fall in SpO(2) >/=4% or Sp0(2) <90%. Regression analyses helped determine the association between these variables and all cause and respiratory mortality. Results The 6MWD was a good predictor of all-cause and respiratory mortality primarily in patients with FEV(1) <50% (p <0.001) after adjusting for all the co-variates. Patients who desaturated during the 6MWT had a higher mortality than patients who did not desaturate (67% vs 38%, p <0.001). Oxygen desaturation predicted mortality (RR 2.63; 95%CI: 1.53-4.51, p <0.001), but with less power than PaO(2) at rest. Conclusions The 6MWD helps predict mortality primarily in patients with severe COPD. Although the oxygen desaturation profile during the 6MWT improves the predictive ability of the 6MWD, it appears to be of less relevance than in other lung diseases and than the resting PaO(2).
PMID: 18625667 [PubMed - as supplied by publisher]