Prediction of oxygen uptake during walking in ambulatory persons with multiple sclerosis.

Abstract

People with multiple sclerosis (MS) have an increased rate of gross oxygen uptake (gross-VO2) during treadmill walking, and their gross-VO2 may further vary with walking impairment. This study attempted to develop an equation for predicting gross-VO2 from walking speed and an index of walking impairment in persons with MS and examine its accuracy. Gross-VO2 was measured with open-circuit spirometry in 43 persons with MS (47 +/- 9 yr; 38 women) during five treadmill walking trials, each lasting 6 min, at 2.0, 2.5, 3.0, 3.5, and 4.0 mph (0.89, 1.12, 1.34, 1.56, and 1.79 m/s). The 12-Item Multiple Sclerosis Walking Scale (MSWS-12) and the single-item Patient Determined Disease Steps scale (PDDS) provided indices of walking impairment. Multilevel modeling with random intercepts and slopes showed significant effects of speed and MSWS-12 on gross-VO2 (p </= 0.014; R(2) = 0.70). PDDS was not a significant predictor. Gross-VO2 estimated by the regression equation did not differ from actual gross-VO2 across speeds. Mean absolute prediction error across speeds was 9.1%. The Bland-Altman plot indicated zero mean difference between actual and predicted gross-VO2 with modest 95% confidence intervals. Therefore, speed and MSWS-12 score are jointly highly predictive of gross-VO2 during treadmill walking in persons with MS.