Effects of respiratory muscle unloading on leg muscle oxygenation and blood volume during high-intensity exercise in chronic heart failure

Effects of respiratory muscle unloading on leg muscle oxygenation and blood volume during high-intensity exercise in chronic heart failure

Author Borghi-Silva, Audrey Autor UNIFESP Google Scholar
Carrascosa, Claudia Autor UNIFESP Google Scholar
Oliveira, Cristino Carneiro Autor UNIFESP Google Scholar
Barroco, Adriano C. Autor UNIFESP Google Scholar
Berton, Danilo C. Autor UNIFESP Google Scholar
Vilaca, Debora Autor UNIFESP Google Scholar
Lira-Filho, Edgar B. Autor UNIFESP Google Scholar
Ribeiro, Dirceu Autor UNIFESP Google Scholar
Nery, Luiz Eduardo Autor UNIFESP Google Scholar
Neder, J. Alberto Autor UNIFESP Google Scholar
Institution Universidade Federal de São Paulo (UNIFESP)
Abstract Blood flow requirements of the respiratory muscles (RM) increase markedly during exercise in chronic heart failure (CHF). We reasoned that if the RM could subtract a fraction of the limited cardiac output (QT) from the peripheral muscles, RM unloading would improve locomotor muscle perfusion. Nine patients with CHF ( left ventricle ejection fraction = 26 +/- 7%) undertook constant-work rate tests (70-80% peak) receiving proportional assisted ventilation (PAV) or sham ventilation. Relative changes (Delta%) in deoxy-hemoglobyn, oxi-Hb ([O(2)Hb]), tissue oxygenation index, and total Hb ([Hb(TOT)], an index of local blood volume) in the vastus lateralis were measured by near infrared spectroscopy. in addition, QT was monitored by impedance cardiography and arterial O-2 saturation by pulse oximetry (SpO(2)). There were significant improvements in exercise tolerance (Tlim) with PAV. Blood lactate, leg effort/Tlim and dyspnea/Tlim were lower with PAV compared with sham ventilation (P < 0.05). There were no significant effects of RM unloading on systemic O-2 delivery as QT and SpO2 at submaximal exercise and at Tlim did not differ between PAV and sham ventilation (P > 0.05). Unloaded breathing, however, was related to enhanced leg muscle oxygenation and local blood volume compared with sham, i.e., higher Delta[O(2)Hb]% and Delta[Hb(TOT)]%, respectively (P < 0.05). We conclude that RM unloading had beneficial effects on the oxygenation status and blood volume of the exercising muscles at similar systemic O-2 delivery in patients with advanced CHF. These data suggest that blood flow was redistributed from respiratory to locomotor muscles during unloaded breathing.
Keywords blood flow
cardiac failure
cardiovascular physiology
oxygen consumption
Language English
Date 2008-06-01
Published in American Journal of Physiology-heart and Circulatory Physiology. Bethesda: Amer Physiological Soc, v. 294, n. 6, p. H2465-H2472, 2008.
ISSN 0363-6135 (Sherpa/Romeo, impact factor)
Publisher Amer Physiological Soc
Extent H2465-H2472
Origin http://dx.doi.org/10.1152/ajpheart.91520.2007
Access rights Open access Open Access
Type Article
Web of Science ID WOS:000256497300007
URI http://repositorio.unifesp.br/handle/11600/30678

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