Individual differences in breathlessness during exercise, as related to ventilatory chemosensitivities in humans

1. The present study attempted to test the hypothesis that breathlessness associated with exercise hyperpnoea is greater in subjects with greater activities of the central and peripheral chemoreceptors during exercise. The chemoreceptor activities were assessed by resting estimates of hypercapnic ventilatory response (delta VE/delta PCO2, HCVR) and hypoxic ventilatory response (delta VE/-delta SO2, HVR), respectively, where VE is minute ventilation and SO2 is oxygen saturation. 2. Nine female and nine male subjects performed a 1 min incremental exercise test until exhaustion, during which breathlessness intensity (BS), assessed by a Borg category scale, and VE were measured every minute. The maximum O2 uptake (VO2,max) was also determined. 3. Using a stepwise multiple linear regression analysis, the relative contributions of not only VE, HCVR and HVR, but also VO2,max and a predicted maximum voluntary ventilation (MVVp) of the individuals to BS, were examined. 4. The analysis showed that BS = 0.1VE + 4.9HVR - 0.03MVVp + 0.55 (r2 = 0.71), indicating that VE accounted for 44% of the variance of BS, HVR for 12% and MVVp for 15%. No significant relation of HCVR and VO2,max to BS was found. 5. These results suggest a contribution of peripheral chemoreceptors to the generation of exertional breathlessness.