Proposing a standardized method for evaluating patient report of the intensity of dyspnea during exercise testing in COPD

BACKGROUND Measuring dyspnea intensity associated with exercise provides insights into dyspnea-limited exercise capacity, and has been used to evaluate treatment outcomes for chronic obstructive pulmonary disease (COPD). Three patient-reported outcome scales commonly cited for rating dyspnea during exercise are the modified Borg scale (MBS), numerical rating scale for dyspnea (NRS-D), and visual analogue scale for dyspnea (VAS-D). Various versions of each scale were found. Our objective was to evaluate the content validity of scales commonly used in COPD studies, to explore their ability to capture patients' experiences of dyspnea during exercise, and to evaluate a standardized version of the MBS. METHODS A two-stage procedure was used, with each stage involving one-on-one interviews with COPD patients who had recently completed a clinic-based exercise event on a treadmill or cycle ergometer. An open-ended elicitation interview technique was used to understand patients' experiences of exercise-induced dyspnea, followed by patients completing the three scales. The cognitive interviewing component of the study involved specific questions to evaluate the patients' perspectives of the content and format of the scales. Results from Stage 1 were used to develop a standardized version of the MBS, which was then subjected to further content validity assessment during Stage 2. RESULTS Thirteen patients participated in the two-stage process (n = 6; n = 7). Mean forced expiratory volume in 1 second (FEV(1)) percent predicted was 40%, mean age 57 years, and 54% were male. Participants used a variety of terms to describe the intensity and variability of exercise-induced dyspnea. Subjects understood the instructions and format of the standardized MBS, and were able to easily select a response to report the level of dyspnea associated with their recent standardized exercise. CONCLUSION This study provides initial evidence in support of using a standardized version of the MBS version for quantifying dyspnea intensity associated with exercise in patients with COPD.