The validity of cardiopulmonary exercise testing for assessing aerobic capacity in neuromuscular diseases.

Abstract

ObjectivesTo determine the content validity of cardiopulmonary exercise testing (CPET) for assessing peak oxygen uptake (VO2peak) in neuromuscular diseases (NMD). DesignBaseline assessment of a randomized controlled trial. SettingAcademic hospital. ParticipantsEighty-six adults (age: 58.0 ± 13.9 years) with Charcot-Marie-Tooth disease (n=35), post-polio syndrome (n=26), or other NMD (n=25). InterventionNot applicable. Main Outcome MeasuresWorkload, gas exchange variables, heart rate, and ratings of perceived exertion were measured during CPET on a cycle ergometer, supervised by an experienced trained assessor. Muscle strength of the knee extensors was assessed isometrically with a fixed dynamometer. Criteria for confirming maximal cardiorespiratory effort during CPET were established during 3 consensus meetings with an expert group. The percentage of participants meeting these criteria was assessed to quantify content validity. ResultsThe following criteria were established for maximal cardiorespiratory effort; a plateau in oxygen uptake (VO2plateau) as primary criterion, or 2 out of 3 secondary criteria; 1) peak respiratory exchange ratio (RERpeak) ≥1.10, 2), peak heart rate (HRpeak) ≥85% of predicted maximal heart rate, and 3) peak rating of perceived exertion (RPEpeak) ≥17 on the 6-20 Borg scale. These criteria were attained by 71 participants (83%). VO2plateau, RERpeak ≥1.10, HRpeak ≥85%, and RPEpeak ≥17 were attained by respectively 31%, 73%, 69%, and 72% of the participants. Peak workload, VO2peak, and knee extension muscle strength were significantly higher, and body mass index was lower (all p<0.05), in participants with maximal cardiorespiratory effort compared to other participants. ConclusionsMost people with NMD achieved maximal cardiorespiratory effort during CPET. Therewith, this study provides high quality evidence of sufficient content validity of VO2peak as a maximal aerobic capacity measure. Content validity may be lower in more severely affected people with lower physical fitness.