Exertional dyspnea associated with chest wall strapping is reduced when external dead space substitutes for part of the exercise stimulus to ventilation.
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 exercise. Eleven healthy men undertook a randomized controlled crossover trial that compared four constant work exercise conditions:1) control (CTRL): unrestricted breathing at 90% gas exchange threshold (GET);2) CTRL+dead space (DS): unrestricted breathing with 0.6-l dead space, at isoventilation to CTRL due to reduced exercise intensity;3) CWS: chest wall strapping at 90% GET; and4) CWS+DS: chest strapping with 0.6-l dead space, at isoventilation to CWS with reduced exercise intensity. Chest strapping reduced forced vital capacity by 30.4 ± 2.2% (mean ± SE). Dyspnea at isoventilation was unchanged with CTRL+DS compared with 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 with CWS (3.40 ± 0.52 and 4.51 ± 0.53, respectively;P= 0.003). Perceived leg fatigue was reduced with CTRL+DS compared with CTRL (2.36 ± 0.48 and 2.86 ± 0.59, respectively;P= 0.049) and lower with CWS+DS compared with CWS (1.86 ± 0.30 and 4.00 ± 0.79, respectively;P= 0.006). With unrestricted breathing, dead space did not change dyspnea at isoventilation, suggesting 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, raising the possibility that leg muscle work contributes to dyspnea perception independent of the ventilatory stimulus.NEW & NOTEWORTHYChest wall strapping was applied to healthy humans to simulate restrictive lung disease. With chest wall strapping, dyspnea was reduced when dead space substituted for part of a constant exercise stimulus to ventilation. Dyspnea associated with chest wall strapping depended on the contribution of leg muscle work to ventilatory stimulation. Chest wall strapping might not be a clinically relevant model to determine whether an alternative reflex ventilatory stimulus mimics the intensity of exertional dyspnea.
Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia; luke.garske@connect.qut.edu.au.|Respiratory and Sleep Medicine, Princess Alexandra Hospital, Brisbane, Queensland, Australia.
Luke A
LA
Garske
Allied Health Sciences and Menzies Health Institute of Queensland, Griffith University, Gold Coast, Queensland, Australia.
Ravin
R
Lal
Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
Ian B
IB
Stewart
Allied Health Sciences and Menzies Health Institute of Queensland, Griffith University, Gold Coast, Queensland, Australia.
Norman R
NR
Morris
Allied Health Sciences and Menzies Health Institute of Queensland, Griffith University, Gold Coast, Queensland, Australia.|Division of Cardiovascular Diseases, Mayo Clinic, Rochester, Minnesota; and.
Troy J
TJ
Cross
Allied Health Sciences and Menzies Health Institute of Queensland, Griffith University, Gold Coast, Queensland, Australia.
Lewis
L
Adams
D000293:Adolescent; D000328:Adult; D018592:Cross-Over Studies; D004417:Dyspnea / Q000503:physiopathology; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test / Q000379:methods; D006801:Humans; D008168:Lung / Q000502:physiology*; D008176:Lung Volume Measurements / Q000379:methods; D008297:Male; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012119:Respiration; D012126:Respiratory Dead Space / Q000502:physiology*; D012129:Respiratory Function Tests / Q000379:methods; D035441:Thoracic Wall / Q000502:physiology*; D014691:Ventilation / Q000379:methods; D055815:Young Adult
chest wall strapping; dead space; dyspnea; restrictive lung disease; ventilatory stimulation