Further specification and evaluation of a new clinical index for dyspnea.

When breathlessness is described in conventional clinical indexes-such as the Pneumoconiosis Research Unit score or the Medical Research Council index-the ratings depend only on the magnitude of the most taxing task that the patient can perform. No attention is given to the patient's effort in performing tasks or to the functional impairment produced by dyspnea in everyday activities. To improve the effectiveness and scope of the assessment, the patient's magnitude of effort and task, as well as functional impairment, were combined in a recently developed new index of dyspnea. In the current research, this new index has been further improved and tested. The ratings have been cited with more precise criteria, and the results of the Modified Dyspnea Index created by the new criteria have been compared with results of the conventional Pneumoconiosis Research Unit score, and with physiologic measurements of pulmonary function. For 32 patients with stable chronic obstructive pulmonary disease (COPD), the Modified Dyspnea Index had a moderate correlation with the Pneumoconiosis Research Unit score (Spearman rho = -0.62) and with the FEV1 (Pearson r = 0.71) and FVC (Pearson r = 0.69). Among patients with the same Pneumoconiosis Research Unit score, however, the Modified Dyspnea Index scores showed a substantial gradient. Ratings with both the previous and the modified new dyspnea indexes correlated most strongly with respiratory muscle strength, supporting the idea that dyspnea is mediated by alteration of respiratory muscle function.(ABSTRACT TRUNCATED AT 250 WORDS)