title: Deep breathing heart rate variability is associated with inspiratory muscle weakness in chronic heart failure.
abstract: OBJECTIVE
  There is a synchronism between the respiratory and cardiac cycles. However, the relationship of inspiratory muscle weakness in chronic heart failure (CHF) on cardiac autonomic modulation is unknown. The purpose of the present investigation was to evaluate the impact of inspiratory muscle strength on the magnitude of respiratory sinus arrhythmia.
  
  
  METHODS
  Ten CHF (62 ± 7 years--left ventricle eject fraction of 40 ± 5% and New York Heart Association class I-III) and nine matched-age healthy volunteers (64 ± 5 years) participated in this study. Heart rate variability (HRV) was obtained at rest and during deep breathing manoeuvre (DB-M) by electrocardiograph.
  
  
  RESULTS
  CHF patients demonstrated impaired cardiac autonomic modulation at rest and during DB-M when compared with healthy subjects (p < 0.05). Moreover, significant and positive correlations between maximal inspiratory pressure and inspiratory-expiratory differences (r = 0.79), expiratory/inspiratory ratio (r = 0.83), root mean square of the successive differences (r = 0.77), standard deviation of NN intervals (r = 0.77), low frequency (r = 0.77), and high frequency (r = 0.70) were found during DB-M. At rest, significant correlations were found also.
  
  
  CONCLUSIONS
  Patients with CHF presented impaired cardiac autonomic modulation at rest. In addition, cardiac autonomic control of heart rate was associated with inspiratory muscle weakness in CHF. Based on this evidence, recommendations for future research applications of respiratory muscle training can bring to light a potentially valuable target for rehabilitation.
authors.affiliation: Department of Physiotherapy, School of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Cardiopulmonary Physiotherapy Laboratory, Nucleus of Research in Physical Exercise, Federal University of São Carlos, São Carlos, São Paulo, Brazil.
authors.forename: Michel Silva
authors.initials: MS
authors.lastname: Reis
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.forename: Bruno
authors.initials: B
authors.lastname: Archiza
authors.forename: Carlos Fischer
authors.initials: CF
authors.lastname: de Toledo
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 / Q000503:physiopathology; D001341:Autonomic Nervous System / Q000503:physiopathology; D016022:Case-Control Studies; D002908:Chronic Disease; D003430:Cross-Sectional Studies; D004562:Electrocardiography; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D018908:Muscle Weakness / Q000503:physiopathology* / Q000628:therapy; D026741:Physical Therapy Modalities; D012132:Respiratory Muscles / Q000503:physiopathology*; D012146:Rest / Q000502:physiology
keywords: chronic heart failure; heart rate variability; inspiratory muscle strength; respiratory sinus arrhythmia