title: Effect of limb muscle fatigue on perception of respiratory effort in healthy subjects.
abstract: The role of nonrespiratory peripheral afferents in dyspnea perception has not been fully elucidated yet. Our hypothesis is that fatigue-induced activation of limb muscle metaboreceptors served by group IV fine afferent fibers may impact on respiratory effort perception. We studied 12 healthy subjects breathing against progressive inspiratory resistive loads (10, 18, 30, 40, and 90 cmH(2)O x l(-1) x s) before and after inducing low-frequency fatigue of quadriceps muscle by repeating sustained contractions at > or = 80% of maximal voluntary contraction. Subjects also underwent a sham protocol while performing two loaded breathing runs without muscle fatigue in between. During the loaded breathing, while subjects mimicked the quiet breathing pattern using a visual feedback, ventilation, tidal volume, respiratory frequency, pleural pressure swings, arterial oxygen saturation, end-tidal partial pressure of CO(2), and dyspnea by a Borg scale were recorded. Compared with prefatigue, limb muscle fatigue resulted in a higher increase in respiratory effort perception for any given ventilation, tidal volume, respiratory frequency, pleural pressure swings, end-tidal partial pressure of CO(2), and arterial oxygen saturation. No difference between the two runs was observed with the sham protocol. The present data support the hypothesis that fatigue of limb muscles increases respiratory effort perception associated with loaded breathing, likely by the activation of limb muscle metaboreceptors.
authors.affiliation: Dept. of Internal Medicine, Section of Clinical Immunology and Respiratory Diseases, Univ. of Florence, Viale G.B. Morgagni, 85, 50134 Florence, Italy.
authors.forename: Antonello
authors.initials: A
authors.lastname: Grippo
authors.forename: Riccardo
authors.initials: R
authors.lastname: Carrai
authors.forename: Linda
authors.initials: L
authors.lastname: Chiti
authors.forename: Giulia Innocenti
authors.initials: GI
authors.lastname: Bruni
authors.forename: Giorgio
authors.initials: G
authors.lastname: Scano
authors.forename: Roberto
authors.initials: R
authors.lastname: Duranti
mesh_terms: D000328:Adult; D004417:Dyspnea / Q000503:physiopathology* / Q000523:psychology; D004558:Electric Stimulation; D015444:Exercise; D056228:Feedback, Sensory; D005260:Female; D005267:Femoral Nerve / Q000503:physiopathology; D006801:Humans; D008168:Lung / Q000294:innervation / Q000503:physiopathology*; D008297:Male; D009119:Muscle Contraction; D018763:Muscle Fatigue; D009475:Neurons, Afferent / Q000502:physiology; D010100:Oxygen / Q000097:blood; D010465:Perception; D010791:Phrenic Nerve / Q000503:physiopathology; D012123:Pulmonary Ventilation; D052097:Quadriceps Muscle / Q000294:innervation / Q000503:physiopathology*; D012119:Respiration; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics; D013990:Tidal Volume
chemical_list: D010100:Oxygen