Predicting oxygen uptake for men with moderate to severe chronic obstructive pulmonary disease

Abstract

Background: Measurement of the maximum oxygen uptake in patients with chronic obstructive pulmonary disease (COPD) has been used to determine the intensity of exercise and to estimate the patient's response to treatment during pulmonary rehabilitation. However, cardiopulmonary exercise testing is not widely available in Korea. The 6-minute walk test (6MWT) is a simple method of measuring the exercise capacity of a patient. It also provides high reliability data and it reflects the fluctuation in one' s exercise capacity relatively well with using the standardized protocol. The prime objective of the present study is to develop a regression equation for estimating the peak oxygen uptake (VO2) for men with moderate to very severe COPD from the results of a 6MWT. Methods: A total of 33 male patients with moderate to very severe COPD agreed to participate in this study. Pulmonary function testing, cardiopulmonary exercise testing and a 6MWT were performed on their first visits. The index of work (6Mwork, 6-minute walk distance [6MWD]xbody weight) was calculated for each patient. Those variables that were closely related to the peak VO2 were identified through correlation analysis. With including such variables, the equation to predict the peak VO2 was generated by the multiple linear regression method. Results: The peak VO2 averaged 1,015±392 ml/min, and the mean 6MWD was 516±195 meters. The 6Mwork (r=.597) was better correlated to the peak VO2 than the 6MWD (r=.415). The other variables highly correlated with the peak VO2 were the FEV1 (r=.742), DLco (r=.734) and FVC (r=.679). The derived prediction equation was VO2 (ml/min)=(274.306xFEV1)+(36.242xDLco)+(0.007x6Mwork)-84. 867. Conclusion: Under the circumstances when measurement of the peak VO 2 is not possible, we consider the 6MWT to be a simple alternative to measuring the peak VO2. Of course, it is necessary to perform a trial on much larger scale to validate our prediction equation.