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A respiratory response to the activation of the muscle metaboreflex during concurrent hypercapnia in man
Author(s) -
Lykidis Christos K.,
Kumar Prem,
Vianna Lauro C.,
White Michael J.,
Balanos George M.
Publication year - 2010
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/expphysiol.2009.049999
Subject(s) - hypercapnia , respiratory minute volume , ventilation (architecture) , isometric exercise , medicine , anesthesia , cardiology , respiratory system , mechanical engineering , engineering
In this study, we aimed to assess the ventilatory and cardiovascular responses to the combined activation of the muscle metaboreflex and the ventilatory chemoreflex, achieved by postexercise circulatory occlusion (PECO) and euoxic hypercapnia (end‐tidal partial pressure of CO 2 7 mmHg above normal), respectively. Eleven healthy subjects (4 women and 7 men; 29 ± 4.4 years old; mean ± s.d. ) undertook the following four trials, in random order: 2 min of isometric handgrip exercise followed by 2 min of PECO with hypercapnia; 2 min of isometric handgrip exercise followed by 2 min of PECO while breathing room air; 4 min of rest with hypercapnia; and 4 min of rest while breathing room air. Ventilation was significantly increased during exercise in both the hypercapnic (+3.17 ± 0.82 l min −1 ) and the room air breathing trials (+2.90 ± 0.26 l min −1 ; all P < 0.05). During PECO, ventilation returned to pre‐exercise levels when breathing room air (+0.52 ± 0.37 l min −1 ; P > 0.05), but it remained elevated during hypercapnia (+3.77 ± 0.23 l min −1 ; P < 0.05). The results indicate that the muscle metaboreflex stimulates ventilation with concurrent chemoreflex activation. These findings have implications for disease states where effort intolerance and breathlessness are linked.