Chest
Volume 108, Issue 2, August 1995, Pages 452-459
Journal home page for Chest

Clinical Investigations; Articles; Selected Reports
The Relationship of the 6-Min Walk Test to Maximal Oxygen Consumption in Transplant Candidates With End-Stage Lung Disease

https://doi.org/10.1378/chest.108.2.452Get rights and content

Study objective

To assess the relationship of distance amhulated during the 6-min walk test (6'WT) to maximal oxygen consumption ( V˙o2 max).

Setting

Pre-lung transplant evaluation.

Patients

60 patients (22 men, 38 women; mean age, 44 years) with end-stage lung disease (mean FEV1 and forced vital capacity of 0.97 and 1.93, respectively).

Measurements and results

The 6'WT was performed on a level hallway surface, and V˙o2 max was obtained during maximal cycle ergometry exercise testing with respiratory gas analysis. Multivariate analysis of patient characteristics (age, sex, weight, FEV1, FVC, diffusing capacity for carbon monoxide (DCO), 6'WT distance ambulated, number of rests per 6'WT, and the maximal heart rate, blood pressure, rate-pressure product, respiratory rate, oxygen saturation, rating of perceived exertion, and amount of supplemental oxygen used during the 6'WT) was performed on two groups of 30 patients each (group A or B) who were randomly assigned to either group by a process of random selection using a computer-generated random numbers program. Distance ambulated was the strongest independent predictor of V˙o2 max (r=0.73; p<0.0001) in both groups, and adding age, weight, and pulmonary function test results (FVC, FEV1, and DCO) to the regression equation increased the correlation coefficient to 0.83. Because of the significant correlation of distance ambulated during the 6'WT to V˙o2 max, the prediction equation obtained from the multivariate analysis of group A, V˙o2 max= 0.006×distance (feet) +3.38, was used to estimate the V˙o2 max of the group B patients. No significant difference was observed between the estimated (x±SD= 8.9±2.4 mL/kg/min) and observed (x±SD=9.4±3.8 mL/kg/min) V˙o2 max (mean difference, 0.5 mL/kg/min; SD of the difference=2.88).

Conclusions

The distance ambulated during a 6'WT can predict V˙o2 max in patients with end-stage lung disease. The addition of several patient characteristics can increase the ability to predict V˙o2 max and account for more of the variability. Such information is valuable when assessing patient response to therapeutic intervention if respiratory gas analysis is unavailable or impractical.

(CHEST 1995; 108:452-59)

Section snippets

Patient Population

Sixty patients with end-stage lung disease who were undergoing pre-lung transplant evaluation served as subjects. The criteria necessary for transplantation included any end-stage pulmonary condition or disease resulting in frequent hospitalizations, progressive deterioration of pulmonary function, the inability to perform normal daily activities, and a life expectancy of less than 18 months. The patient characteristics are listed in Table 1. Patients with psychological impairment (ie, severe

Exercise Testing and Respiratory Gas Analysis

Several of the variables obtained from the maximal symptom-limited bicycle ergometry exercise tests with respiratory gas analysis are shown in Table 1. There was no significant difference between groups in any of the exercise test variables.

The mean exercise duration of groups A and B was 4.45±1.9 and 4.15 ±2.15 mins, respectively, with a maximal workload of 34.5±22 and 35.7±27 W, respectively. The mean maximal VT of groups A and B was 867±276 and 905 ±308 mL, respectively, with a mean increase

Discussion

The results of this study suggest that the distance ambulated during a 6'WT may predict V˙o2 max in patients with end-stage lung disease. The respectable correlation of distance ambulated during the 6'WT to V˙o2 max and the development of several regression equations to easily predict V˙o2 max in patients with end-stage lung disease are the major contributions of this study. The ability to predict V˙o2 max may be helpful in evaluating patient status, prescribing an effective

Summary

No previous study has evaluated the relationship of the 6'WT to V˙o2 max. This study has shown that the 6'WT total distance ambulated is the strongest independent correlate to V˙o2 max and that it can predict V˙o2 max in patients with end-stage lung disease but accounts for only 54% of the variability. The addition of age and weight, as well as pulmonary function test results (DCO, FEV1, and FVC) did increase the ability to predict V˙o2 max and account for more of the

References (34)

  • CoatsAJS et al.

    Controlled trial of physical training in chronic heart failure: exercise performance, hemodynamics, ventilation, and autonomic function

    Circulation

    (1992)
  • RogersTK et al.

    Pulmonary hemodynamics and physical training in patients with chronic obstructive pulmonary disease

    Chest

    (1992)
  • ManciniDM et al.

    Value of peak exercise oxygen consumption for optimal timing of cardiac transplantation in ambulatory patients with heart failure

    Circulation

    (1992)
  • CooperKH

    A means of assessing maximal oxygen intake

    JAMA

    (1968)
  • American ThoracicSociety

    Standardization of spirometry—1987 update

    Am Rev Respir Dis

    (1987)
  • American ThoracicSociety

    Single breath carbon monoxide diffusion capacity (transfer factor): recommendations for standard technique

    Am Rev Respir Dis

    (1987)
  • CotesJE

    Lung function assessment and application in medicine

    (1979)
  • Cited by (194)

    • General Thoracic Surgery

      2021, Perioperative Medicine: Managing for Outcome, Second Edition
    View all citing articles on Scopus
    View full text