title: Tolerance and physiological correlates of neuromuscular electrical stimulation in COPD: a pilot study.
abstract: BACKGROUND
  Neuromuscular electrical stimulation (NMES) of the lower limbs is an emerging training strategy in patients with COPD. The efficacy of this technique is related to the intensity of the stimulation that is applied during the training sessions. However, little is known about tolerance to stimulation current intensity and physiological factors that could determine it. Our goal was to find potential physiological predictors of the tolerance to increasing NMES stimulation intensity in patients with mild to severe COPD.
  
  
  METHODS
  20 patients with COPD (FEV1 = 54±14% pred.) completed 2 supervised NMES sessions followed by 5 self-directed sessions at home and one final supervised session. NMES was applied simultaneously to both quadriceps for 45 minutes, at a stimulation frequency of 50 Hz. Spirometry, body composition, muscle function and aerobic capacity were assessed at baseline. Cardiorespiratory responses, leg discomfort, muscle fatigue and markers of systemic inflammation were assessed during or after the last NMES session. Tolerance to NMES was quantified as the increase in current intensity from the initial to the final NMES session (ΔInt).
  
  
  RESULTS
  Mean ΔInt was 12±10 mA. FEV1, fat-free-mass, quadriceps strength, aerobic capacity and leg discomfort during the last NMES session positively correlated with ΔInt (r = 0.42 to 0.64, all p≤0.06) while post/pre NMES IL-6 ratio negatively correlated with ΔInt (r = -0.57, p = 0.001). FEV1, leg discomfort during last NMES session and post/pre IL-6 ratio to NMES were independent factors of variance in ΔInt (r2 = 0.72, p = 0.001).
  
  
  CONCLUSIONS
  Lower tolerance to NMES was associated with increasing airflow obstruction, low tolerance to leg discomfort during NMES and the magnitude of the IL-6 response after NMES.
  
  
  BACKGROUND
  ClinicalTrials.gov NCT00809120.
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada; Univ. Grenoble Alpes, HP2 (Hypoxia: respiratory and cardiovascular physiopathology), Grenoble, France; Inserm HP2 (Hypoxia: respiratory and cardiovascular physiopathology), Grenoble, France; Centre Hospitalier de Grenoble, Grenoble, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Vivodtzev
authors.affiliation: Département de physiothérapie, CHA-Hôpital de l'Enfant-Jésus, Québec, Canada.
authors.forename: Benoit
authors.initials: B
authors.lastname: Rivard
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Philippe
authors.initials: P
authors.lastname: Gagnon
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Vincent
authors.initials: V
authors.lastname: Mainguy
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Annie
authors.initials: A
authors.lastname: Dubé
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Marthe
authors.initials: M
authors.lastname: Bélanger
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: Brigitte
authors.initials: B
authors.lastname: Jean
authors.affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.
authors.forename: François
authors.initials: F
authors.lastname: Maltais
mesh_terms: D000368:Aged; D001823:Body Composition / Q000502:physiology; D004599:Electric Stimulation Therapy / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D018836:Inflammation Mediators / Q000097:blood; D015850:Interleukin-6 / Q000097:blood; D008297:Male; D008875:Middle Aged; D018763:Muscle Fatigue / Q000502:physiology; D053580:Muscle Strength / Q000502:physiology; D018482:Muscle, Skeletal / Q000503:physiopathology; D009469:Neuromuscular Junction / Q000502:physiology*; D010865:Pilot Projects; D029424:Pulmonary Disease, Chronic Obstructive / Q000097:blood / Q000503:physiopathology* / Q000628:therapy*; D052097:Quadriceps Muscle / Q000503:physiopathology; D016896:Treatment Outcome
chemical_list: D018836:Inflammation Mediators; D015850:Interleukin-6