Dyspnea and the mechanics of breathing during progressive exercise

This study investigates dyspnea and the mechanics of breathing during progressive exercise. Three subject groups, athletes, normal sedentary subjects and chronic obstructive diseased patients were studied during progressive exercise testing to exhaustion on a cycle ergometer. Subjects rated dyspnea on a Borg Scale. Inspiratory flow, esophageal/gastric pressures and rib cage/abdominal displacements were measured.Subjects demonstrated two patterns of dyspnea response to changes in esophageal (pleural) pressure. All athletes, two normals and five patients were termed "low dyspnea responders", (LDR), whereas the remaining subjects were termed "high dyspnea responders", (HDR).LDR demonstrated large, rapid negative gastric pressure swings, coupled with outward abdominal displacement during early inspiration when compared to HDR, suggesting that LDR utilized abdominal muscle relaxation at the onset of inspiration. This mechanism appears to provide an extra inspiratory force, contributing to the increasing pleural pressures required. This breathing pattern appears to diminish the sensation of dyspnea at a given pleural pressure