Ventilatory drive modulates the temporal evolution of multidimensional dyspnoea during constant-load exercise in healthy adults

Abstract

How increased ventilatory drive shapes the temporal evolution and multidimensional experience of exertional dyspnoea remains incompletely understood. This study examined whether experimentally increasing ventilatory drive via dead-space loading (DSL) alters dyspnoea during constant-load exercise. Nine healthy adults (7 male; 𝑉̇O₂𝑝𝑒𝑎𝑘 100 ± 16% predicted) performed constant-load cycle ergometry to task failure at 50%Δ between the gas-exchange threshold and 𝑉̇O₂𝑝𝑒𝑎𝑘 under control (CTRL) and DSL (15% vital capacity) conditions in a randomised crossover design. Dyspnoea intensity, dyspnoea unpleasantness, and leg discomfort were assessed using the Borg CR10 scale, and sensory-perceptual and affective-emotional dimensions using the Multidimensional Dyspnoea Profile. Compared with CTRL, DSL increased end-tidal CO₂, minute ventilation, tidal volume, and inspiratory pressures without altering cardiometabolic responses, and reduced time to task failure (10.0 ± 2.3 vs. 13.8 ± 4.6 min; 𝑝 = .012). Dyspnoea intensity rose more rapidly during DSL, but was similar at task failure, whereas dyspnoea unpleasantness was consistently higher without a distinct temporal divergence. Leg discomfort and dyspnoea descriptor frequencies did not differ between conditions. Post-exercise multidimensional profiling revealed greater breathing unpleasantness (𝑝 = .008), immediate perception scores (𝑝 = .036), respiratory work/effort (𝑝 = .040), and air hunger (𝑝 = .027), with no differences in emotional response scores. Greater iso-time increases in dyspnoea intensity and unpleasantness were associated with shorter time to task failure (𝑟 = − .82 to − 0.88; 𝑝 ≤ .007). These findings suggest that increased ventilatory drive accelerates dyspnoea development and preferentially augments sensory-perceptual characteristics of dyspnoea, contributing to earlier task failure despite similar end-exercise symptom intensity.