Abstract:We examined the effects of respiratory muscle work [inspiratory (W r-insp); expiratory (W r-exp)] and arterial oxygenation (SpO 2 ) on exerciseinduced locomotor muscle fatigue in patients with chronic obstructive pulmonary disease (COPD). Eight patients (FEV, 48 Ϯ 4%) performed constant-load cycling to exhaustion (Ctrl; 9.8 Ϯ 1.2 min). In subsequent trials, the identical exercise was repeated with 1) proportional assist ventilation ϩ heliox (PAV); 2) heliox (He:21% O 2); 3) 60% O 2 inspirate (hyperoxia); or 4)… Show more
“…This seems to be in line with previous findings of Amann et al 39 , who reported that the high susceptibility to lower-limb muscle fatigue in patients with COPD is in part attributable to insufficient oxygen transport as a consequence of exaggerated arterial hypoxemia and/or excessive respiratory muscle work. Moreover, quadriceps muscle strength was positively related to D L CO in patients with COPD 18 .…”
“…This seems to be in line with previous findings of Amann et al 39 , who reported that the high susceptibility to lower-limb muscle fatigue in patients with COPD is in part attributable to insufficient oxygen transport as a consequence of exaggerated arterial hypoxemia and/or excessive respiratory muscle work. Moreover, quadriceps muscle strength was positively related to D L CO in patients with COPD 18 .…”
“…The perception of fatigue has to be differentiated with objective measurements of fatigue. Most of the studies examining muscle fatigue after exercise in COPD have used a nonvolitional technique: twitch measurement after magnetic stimulation (240,250,(264)(265)(266)(267)(268). Additionally, the EMG median frequency represents a valuable indirect marker to predict contractile fatigue (269).…”
Section: Limb Muscle Function In Copdmentioning
confidence: 99%
“…During strenuous exercise, peripheral vasoconstriction associated with the high demand for respiratory muscle blood flow appears to compromise limb muscle perfusion (261,425,426) and consequently enhance muscle fatigue (427). A blood redistribution phenomenon in favor of the respiratory muscles may also occur in COPD (428), and it has been hypothesized that strategies that reduce respiratory muscle work may alleviate limb muscle fatigue by restoring blood flow to the limb muscles (267,429). This hypothesis was supported by a study from Amann and coworkers, who gave a range of interventions designed to improve oxygenation (by supplemental oxygen) and/or reduce work of breathing (proportional-assist ventilation or helium or both) (267).…”
Section: American Thoracic Society Documentsmentioning
“…Clinically, respiratory muscle fatigue could play an important role in limiting oxygen delivery in patients with obstructive sleep apnea (OSA) (1,24), chronic heart failure (18), and chronic obstructive pulmonary disease (COPD) (2). It is still unclear whether diaphragm fatigue, thereby metaboreflex, leads to alternations in sympathetic nerve activity and cardiovascular variables during dynamic leg exercise at submaximal intensity.…”
Katayama K, Iwamoto E, Ishida K, Koike T, Saito M. Inspiratory muscle fatigue increases sympathetic vasomotor outflow and blood pressure during submaximal exercise. Am J Physiol Regul Integr Comp Physiol 302: R1167-R1175, 2012. First published March 28, 2012 doi:10.1152/ajpregu.00006.2012.-The purpose of this study was to elucidate the influence of inspiratory muscle fatigue on muscle sympathetic nerve activity (MSNA) and blood pressure (BP) response during submaximal exercise. We hypothesized that inspiratory muscle fatigue would elicit increases in sympathetic vasoconstrictor outflow and BP during dynamic leg exercise. The subjects carried out four submaximal exercise tests: two were maximal inspiratory pressure (PImax) tests and two were MSNA tests. In the PI max tests, the subjects performed two 10-min exercises at 40% peak oxygen uptake using a cycle ergometer in a semirecumbent position [spontaneous breathing for 5 min and with or without inspiratory resistive breathing for 5 min (breathing frequency: 60 breaths/min, inspiratory and expiratory times were each set at 0.5 s)]. Before and immediately after exercise, PImax was estimated. In MSNA tests, the subjects performed two 15-min exercises (spontaneous breathing for 5 min, with or without inspiratory resistive breathing for 5 min, and spontaneous breathing for 5 min). MSNA was recorded via microneurography of the right median nerve at the elbow. PImax decreased following exercise with resistive breathing, whereas no change was found without resistance. The time-dependent increase in MSNA burst frequency (BF) appeared during exercise with inspiratory resistive breathing, accompanied by an augmentation of diastolic BP (DBP) (with resistance: MSNA, BF ϩ83.4%; DBP, ϩ23.8%; without resistance: MSNA BF, ϩ19.2%; DBP, Ϫ0.4%, from spontaneous breathing during exercise). These results suggest that inspiratory muscle fatigue induces increases in muscle sympathetic vasomotor outflow and BP during dynamic leg exercise at mild intensity. respiratory muscle; sympathetic outflow; metaboreflex; dynamic leg exercise
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.