The 6-Min Walk Distance, Peak Oxygen Uptake, and Mortality in COPD

doi:10.1378/chest.07-2050

Chest

Volume 132, Issue 6, December 2007, Pages 1778-1785

https://doi.org/10.1378/chest.07-2050 Get rights and content

In patients with COPD, the maximal oxygen uptake ( $\dot{V}$ o₂) measured at peak exercise and the 6-min walk distance (6MWD) have been associated with survival; however, no study has compared the strength of the association in the same patients. In this study, we compared the association between the 6MWD and peak $\dot{V}$ o₂ and mortality in 365 patients with COPD. Patients' cardiopulmonary cycle ergometry test results and 6MWD were determined at entry, and patients were followed up for a mean period of 67 months. There were 171 deaths. Compared with survivors, nonsurvivors were older (mean [± SD] age, 67.9 ± 8 vs 65.9 ± 8 years, respectively; p = 0.008), had worse mean FEV₁ (36.5 ± 12 vs 42.6 ± 14 L, respectively; p = 0.02), had lower mean peak $\dot{V}$ o₂ (9.8 ± 3 vs 11.8 ± 3.6 mL/Kg/min, respectively; p < 0.0001), lower mean 6MWD (312 ± 104 vs 377 ± 95 m, respectively; p < 0.0001), and lower mean exercise minute ventilation (37.4 ± 12 vs 42.3 ± 13 L/min, respectively; p = 0.004). Univariate analysis showed that peak $\dot{V}$ o₂ and 6MWD as well as comorbidity, FEV₁, and body mass index were associated with death. Logistic regression analysis with mortality as the dependent variable revealed that 6MWD (hazard ratio [HR], 0.996; 95% confidence interval [CI], 0.993 to 0.999; p < 0.01) had a stronger association than the peak $\dot{V}$ o₂ (HR, 0.971; 95% CI, 0.959 to 1.000; p = 0.050) with mortality. This study shows the 6MWD is as good predictor of mortality as the peak $\dot{V}$ o₂ in patients with COPD.

Section snippets

Patients

The 365 consecutive patients with symptomatic COPD had been recruited to the body-mass index, airflow obstruction, dyspnea, and exercise capacity (BODE) protocol at the Bay Pines Veterans Administration Health Care System (n = 278) and St. Elizabeth's Medical Center (n = 87) between 1994 and 2005. The human research committees approved the study, and all of the patients gave informed consent. The study enrollment criteria were as follows: smoking history of > 10 pack-years; diagnosis of COPD;

Results

The clinical characteristics of the 365 patients studied are shown in Table 1. As expected, the patients had important airflow limitation, were mostly men, and the group included patients with a wide range of COPD severity.

There were 171 deaths (47%) over the study period (mean period, 66.7 ± 29 months; range, 3 to 121 months). The mean time to death for nonsurvivors was 43 ± 24 months. The majority of patients (50%) died from respiratory failure. However, 9% of deaths were due to

Discussion

This prospective study shows that in patients with a wide range of COPD severity, the 6MWD is as good a predictor, if not a better one, of all-cause mortality as the peak $\dot{V}$ o₂ obtained during a formal CPET. COPD is the fastest-rising major cause of death in the United States, and its prevalence is increasing rapidly.²¹ The severity of the disease has classically been assessed using a single physiologic value, the FEV₁. Although the FEV₁ is a good indicator of disease severity, as the

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: The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

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Chest

Original ResearchCOPDThe 6-Min Walk Distance, Peak Oxygen Uptake, and Mortality in COPD

Section snippets

Patients

Results

Discussion

Semin Thorac Cardiovasc Surg

Chest

Lancet

Arch Bronconeumol

J Clin Epidemiol

Chest

Chest

Chest

Cardiol Clin

Chest

Respiratory muscle function and cardiopulmonary response to exercise in severe COPD

Am J Respir Crit Care Med

Spirometric correlates of improvement in exercise performance after anticholinergic therapy in chronic obstructive pulmonary disease

Am J Respir Crit Care Med

Inhaled bronchodilators reduce dynamic hyperinflation during exercise in patients with chronic obstructive pulmonary disease

Am J Respir Crit Care Med

Functional evaluation of the lung resection candidate

Eur Respir J

Analysis of the factors related to mortality in chronic obstructive pulmonary disease: role of exercise capacity and health status

Am J Respir Crit Care Med

American Thoracic Society statement: guidelines for the six-minute walk test

Am J Respir Crit Care Med

Variables related to increased mortality following out-patient pulmonary rehabilitation

Eur Respir J

Original Research
COPD
The 6-Min Walk Distance, Peak Oxygen Uptake, and Mortality in COPD