QUALITATIVE ASPECTS OF EXERTIONAL DYSPNEA IN PATIENTS WITH INTERSTITIAL LUNG-DISEASE

We compared qualitative and quantitative aspects of perceived exertion al dyspnea in patients with interstitial lung disease (ILD) and normal subjects and sought a physiological rationale for their differences. Twelve patients with ILD [forced vital capacity = 64 +/- 4 (SE) %predi cted] and 12 age-matched normal subjects performed symptom-limited inc remental cycle exercise tests with measurements of dyspnea intensity ( Borg scale), ventilation, breathing pattern, operational lung volumes, and esophageal pressures (Pes). Qualitative descriptors of dyspnea we re selected at exercise cessation. Both groups described increased ''w ork and/or effort'' and ''heaviness'' of breathing; only patients with ILD described ''unsatisfied inspiratory effort'' (75%), ''increased i nspiratory difficulty'' (67%), and ''rapid breathing'' (58%) (P < 0.05 patients with ILD vs. normal subjects). Borg-O-2 uptake ((V) over dot O-2) and Borg-ventilation slopes were significantly greater during ex ercise in patients with ILD (P < 0.01). At peak exercise, when dyspnea intensity and inspiratory effort (Pes-to-maximal inspiratory pressure ratio) were similar, the distinct qualitative perceptions of dyspnea in patients with ILD were attributed to differences in dynamic ventila tory mechancis, i.e., reduced inspiratory capacity, heightened Pes-to- tidal volume ratio, and tachypnea. Factors contributing to dyspnea int ensity in both groups were also different: the best correlate of the B org-(V) over dot O-2 slope in patients with ILD was the resting tidal volume-to-inspiratory capacity ratio (r = 0.58, P < 0.05) and in norma l subjects was the slope of Pes-to-maximal inspiratory pressure ratio over (V) over dot O-2 (r = 0.60, P < 0.05).