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Distance and Oxygen Desaturation During the 6-min Walk Test as Predictors of Long-term Mortality in Patients With COPD

2008; Elsevier BV; Volume: 134; Issue: 4 Linguagem: Inglês

10.1378/chest.08-0520

1931-3543

Ciro Casanova, Claudia Côté, José M. Marı́n, Víctor Pinto-Plata, Juan P. de‐Torres, Armando Aguirre-Jaíme, Carlos Vassaux, Bartolomé R. Celli,

Heart Rate Variability and Autonomic Control

Rationale The distance walked in the 6-min 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 and observed them for at least 3 years (median, 60 months). We measured FEV 1 , body mass index, Pao 2 , Charlson comorbidity score, 6-min walk distance (6MWD), and oxygen saturation by pulse oximetry (Spo 2 ) during the 6MWT. Desaturation was defined as a fall in Spo 2 ≥ 4% or Spo 2 < 90%. Regression analysis 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% of predicted (p < 0.001) after adjusting for all covariates. Patients with desaturation during the 6MWT had a higher mortality rate than patients without desaturation (67% vs 38%, p < 0.001). Oxygen desaturation predicted mortality (relative risk, 2.63; 95% confidence interval, 1.53 to 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 .