Chest wall strapping has been used to assess mechanisms of dyspnea with restrictive lung disease. This study examined the hypothesis that dyspnea with restriction depends principally on the degree of reflex ventilatory stimulation. We compared dyspnea at the same (iso-)ventilation when added dead space provided a component of the ventilatory stimulus during constant work exercise. Eleven healthy males undertook a randomized controlled cross-over trial which compared four constant work exercise conditions (i) CTRL: unrestricted breathing at 90% Gas Exchange Threshold (GET), (ii) CTRL+DS: unrestricted breathing with 0.6 L dead space, at iso-ventilation to CTRL, (iii) CWS: chest strapping at 90% GET, (iv) CWS+DS: chest strapping with 0.6 L dead space, at iso-ventilation to CWS. Dead space was associated with reduced exercise intensity, and chest strapping reduced FVC by 30.4±2.2% (mean ± SE). Dyspnea at iso-ventilation was unchanged with CTRL+DS compared to CTRL (1.93±0.49 and 2.17±0.43, 0-10 numeric rating scale, respectively, P=0.244). Dyspnea was lower with CWS+DS compared to CWS (3.40±0.52 and 4.51±0.53 respectively, P=0.003). Perceived leg fatigue was reduced with CTRL+DS compared to CTRL (2.36±0.48 and 2.86±0.59 respectively, P=0.049) and lower with CWS+DS compared to CWS (1.86±0.30 and 4.00±0.79 respectively, P=0.006). With unrestricted breathing, dead space did not change dyspnea at iso-ventilation, inferring that dyspnea does not depend on the mode of reflex ventilatory stimulation in healthy individuals. With chest strapping, dead space presented a less potent stimulus to dyspnea. This suggests that dyspnea associated with chest strapping depends on the contribution of leg muscle work to ventilatory stimulation.
- dead space
- chest wall strapping
- ventilatory stimulation
- restrictive lung disease
- Copyright © 2016, Journal of Applied Physiology