The data from this investigation increase our understanding of respiratory sensations in ILD. In two previous reports different clinical systems have been described for grading dyspnea during the course of idiopathic pulmonary fibrosis. In addition, psychophysical experiments using both threshold detection and magnitude scaling techniques have been conducted in small numbers of patients with ILD. More recently, we have demonstrated modest correlations between respiratory function and the ratings of dyspnea obtained from the BDI in 23 patients with diverse causes of ILD.22 However, the interrelationships among psychophysical measurements, clinical ratings of dyspnea and physiologic function have not been described.In this study, we evaluated two different approaches for measuring respiratory sensation in symptomatic patients with ILD and compared both with lung function and gas exchange variables. The major findings were: (1) perception of both nonrespiratory (heaviness of weights) and respiratory (elastic loads) tasks was comparable in ILD patients and age-matched control subjects; (2) grades for the MRC, OCD and BDI were significantly interrelated in ILD patients; (3) Dsb and exercise gas exchange correlated with clinical dyspnea ratings but not with the perceived magnitude of added elastic loads; and (4) there were no significant relationships between clinical ratings of dyspnea and psychophysical testing. Reading here
Our findings are consistent with the previous conclusion that exponents for the perception of elastic loads are similar in normal subjects and in patients with ILD when the two groups are matched for age. Furthermore, we found that a subgroup of ILD patients with a higher exponent for magnitude scaling were younger than another subgroup who expressed a lower exponent for magnitude estimations. This result is compatible with the age-related differences in perception of respiratory sensation in normal individuals.- In addition, the results of our study are consistent with the observation that magnitude perception of resistive loads are similar in age-matched healthy individuals and patients with obstructive airway disease. Thus, it appears that patients with chronic respiratory disease have a normal ability to estimate the magnitude of inspiratory loads in the lab.