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This Article Full Text (PDF) All Versions of this Article: chest.08-0520v1 134/4/746    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to My Personal Article Archive Download to citation manager Google Scholar Articles by Casanova, C. Articles by Celli, B. R PubMed PubMed Citation Articles by Casanova, C. Articles by Celli, B. R

DISTANCE AND OXYGEN DESATURATION DURING SIX-MINUTE WALK TEST AS PREDICTORS OF LONG-TERM MORTALITY IN PATIENTS WITH COPD

(1) Pulmonary Department and (2) Research Unit, Hospital La Candelaria, Tenerife and (4) Pulmonary Department, Hospital Miguel Servet, Zaragoza, Spain. (3) Pulmonary Division, Bay Pines VA Medical Center, St Petersburg FL and (5) Pulmonary Division. Caritas-St. Elizabeth's Medical Center, Boston, USA

ccasanova{at}canarias.org

Abstract

RationaleThe 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.

MethodsWe 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 FEV₁, BMI, PaO₂, the Charlson co-morbidity score and distance walked (6MWD) and O₂ saturation (SpO₂) during the 6MWT. Desaturation was defined as a fall in SpO₂ 4% or Sp0₂ <90%. Regression analyses helped determine the association between these variables and all cause and respiratory mortality.

ResultsThe 6MWD was a good predictor of all-cause and respiratory mortality primarily in patients with FEV₁ <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 PaO₂ at rest.

ConclusionsThe 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 PaO₂.

Key Words: COPD • 6-minute walk test • long-term mortality