RT Journal Article
SR Electronic
T1 Locomotor muscle afferents contribute to ventilatory control during exercise in heart failure patients
JF European Respiratory Journal
JO Eur Respir J
FD European Respiratory Society
SP 381
VO 38
IS Suppl 55
A1 Thomas Olson
A1 Michael Joyner
A1 John Eisenach
A1 Timothy Curry
A1 Bruce Johnson
YR 2011
UL http://erj.ersjournals.com/content/38/Suppl_55/381.abstract
AB Background: Reduced ventilatory efficiency is a hallmark of heart failure (HF) and is linked to disease severity and worse prognosis. Mechanisms responsible for altered ventilatory efficiency remain poorly understood but may include neurologic feedback from locomotor muscles. This study was designed to determine the impact of blocking locomotor muscle afferent feedback on ventilation (VE) during exercise in HF patients.Methods: 5 HF patients with reduced systolic function (age=60±11 yrs, ht=1.81±0.03 m, wt=94±7 kg, ejection fraction 27±5%, NYHA class 2±0) underwent two 5 minute submaximal steady-state exercise sessions at 60% peak work (placebo-PLA vs regional neural blockade via intrathecal injection of fentanyl-RNB). Breath-by-breath measures included VE, breathing frequency (fb), tidal volume (VT), end-tidal carbon dioxide (PETCO2), oxygen consumption (VO2), and carbon dioxide production (VCO2). Central chemoreceptor sensitivity was also measured via CO2 rebreathe.Results: At end exercise, there was no difference in VO2 (1.4±0.2 vs 1.4±0.2 L/min, p=0.43). whereas VE was reduced with RNB (48.0±6.5 vs 41.8±6.0 L/min, p<0.05) through a reduction in fb (27.2±5.2 vs 23.9±4.2 breaths/min, p<0.01) with no change in VT (1.8±0.2 vs 1.8±0.2 L/min, p=0.81). Additionally, the VE/VCO2 ratio was reduced (improved) with RNB (33.2±3.5 vs 28.2±2.8, p<0.05). After exercise, there was no difference between the conditions for chemoreceptor sensitivity (VE/PETCO2 slope=2.4±0.9 vs 2.4±0.6, p=0.80).Conclusion: In HF patients, blocking afferent neural feedback from the locomotor muscles during exercise reduces VE and improves ventilatory efficiency. Funded by NIH/NCRR grant KL2-RR024151.