title: Deep breathing heart rate variability is associated with respiratory muscle weakness in patients with chronic obstructive pulmonary disease.
abstract: BACKGROUND
  A synchronism exists between the respiratory and cardiac cycles. However, the influence of the inspiratory muscle weakness in chronic obstructive pulmonary disease (COPD) on cardiac autonomic control is unknown. The purpose of the present investigation was to evaluate the influence of respiratory muscle strength on autonomic control in these patients.
  
  
  METHODS
  Ten chronic obstructive pulmonary disease patients (69+/-9 years; FEV(1)/FVC 59+/-12% and FEV(1) 41+/-11% predicted) and nine age-matched healthy volunteers (64+/-5 years) participated in this study. Heart-rate variability (HRV) was obtained at rest and during respiratory sinusal arrhythmia maneuver (RSA-M) by electrocardiograph.
  
  
  RESULTS
  Chronic obstructive pulmonary disease patients demonstrated impaired cardiac autonomic modulation at rest and during RSA-M when compared with healthy subjects (p<0.05). Moreover, significant and positive correlations between maximal inspiratory pressure (MIP) and the inspiratory-expiratory difference (DeltaIE) (r = 0.60, p<0.01) were found.
  
  
  CONCLUSIONS
  Patients with chronic obstructive pulmonary disease presented impaired sympathetic-vagal balance at rest. In addition, cardiac autonomic control of heart rate was associated with inspiratory muscle weakness in chronic obstructive pulmonary disease. Based on this evidence, future research applications of respiratory muscle training may bring to light a potentially valuable target for rehabilitation.
authors.affiliation: Cardiopulmonary Physiotherapy Laboratory, Nucleus of Research in Physical Exercise, Federal University of São Carlos, São Carlos, SP, Brazil. michelsilre@hotmail.com
authors.forename: Michel Silva
authors.initials: MS
authors.lastname: Reis
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.forename: Ana Paula
authors.initials: AP
authors.lastname: Deus
authors.forename: Rodrigo Polaquini
authors.initials: RP
authors.lastname: Simões
authors.forename: Aparecida Maria
authors.initials: AM
authors.lastname: Catai
authors.forename: Audrey
authors.initials: A
authors.lastname: Borghi-Silva
mesh_terms: D000368:Aged; D001146:Arrhythmia, Sinus / Q000209:etiology; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007320:Inspiratory Capacity; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000150:complications / Q000503:physiopathology*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications / Q000503:physiopathology*; D012119:Respiration; D012129:Respiratory Function Tests; D012132:Respiratory Muscles / Q000503:physiopathology*; D056152:Respiratory Rate / Q000502:physiology; D014797:Vital Capacity
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