title: Relationship between linear and nonlinear dynamics of heart rate and impairment of lung function in COPD patients.
abstract: BACKGROUND
  In chronic obstructive pulmonary disease (COPD), functional and structural impairment of lung function can negatively impact heart rate variability (HRV); however, it is unknown if static lung volumes and lung diffusion capacity negatively impacts HRV responses. We investigated whether impairment of static lung volumes and lung diffusion capacity could be related to HRV indices in patients with moderate to severe COPD.
  
  
  METHODS
  Sixteen sedentary males with COPD were enrolled in this study. Resting blood gases, static lung volumes, and lung diffusion capacity for carbon monoxide (DLCO) were measured. The RR interval (RRi) was registered in the supine, standing, and seated positions (10 minutes each) and during 4 minutes of a respiratory sinus arrhythmia maneuver (M-RSA). Delta changes (Δsupine-standing and Δsupine-M-RSA) of the standard deviation of normal RRi, low frequency (LF, normalized units [nu]) and high frequency (HF [nu]), SD1, SD2, alpha1, alpha2, and approximate entropy (ApEn) indices were calculated.
  
  
  RESULTS
  HF, LF, SD1, SD2, and alpha1 deltas significantly correlated with forced expiratory volume in 1 second, DLCO, airway resistance, residual volume, inspiratory capacity/total lung capacity ratio, and residual volume/total lung capacity ratio. Significant and moderate associations were also observed between LF/HF ratio versus total gas volume (%), r=0.53; LF/HF ratio versus residual volume, %, r=0.52; and HF versus total gas volume (%), r=-0.53 (P<0.05). Linear regression analysis revealed that ΔRRi supine-M-RSA was independently related to DLCO (r=-0.77, r (2)=0.43, P<0.05).
  
  
  CONCLUSIONS
  Responses of HRV indices were more prominent during M-RSA in moderate to severe COPD. Moreover, greater lung function impairment was related to poorer heart rate dynamics. Finally, impaired lung diffusion capacity was related to an altered parasympathetic response in these patients.
authors: Cardiopulmonary Physiotherapy Laboratory, Federal University of São Carlos, São Carlos, Brazil.
authors: Adriana
authors: A
authors: Mazzuco
authors: Pulmonary Function and Clinical Exercise Physiology Unit, Respiratory Division, Department of Medicine, Federal University of São Paulo, São Paulo, Brazil.
authors: Wladimir Musetti
authors: WM
authors: Medeiros
authors: Cardiopulmonary Physiotherapy Laboratory, Federal University of São Carlos, São Carlos, Brazil.
authors: Milena Pelosi Rizk
authors: MP
authors: Sperling
authors: Pulmonary Function and Clinical Exercise Physiology Unit, Respiratory Division, Department of Medicine, Federal University of São Paulo, São Paulo, Brazil.
authors: Aline Soares
authors: AS
authors: de Souza
authors: Pulmonary Function and Clinical Exercise Physiology Unit, Respiratory Division, Department of Medicine, Federal University of São Paulo, São Paulo, Brazil.
authors: Maria Clara Noman
authors: MC
authors: Alencar
authors: Pulmonary Function and Clinical Exercise Physiology Unit, Respiratory Division, Department of Medicine, Federal University of São Paulo, São Paulo, Brazil.
authors: Flávio Ferlin
authors: FF
authors: Arbex
authors: Pulmonary Function and Clinical Exercise Physiology Unit, Respiratory Division, Department of Medicine, Federal University of São Paulo, São Paulo, Brazil ; Laboratory of Clinical Exercise Physiology, Division of Respiratory and Critical Care Medicine, Department of Medicine, Queen's University, Kingston, ON, Canada.
authors: José Alberto
authors: JA
authors: Neder
authors: Department of Physical Therapy and Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois Chicago, Chicago, IL, USA.
authors: Ross
authors: R
authors: Arena
authors: Cardiopulmonary Physiotherapy Laboratory, Federal University of São Carlos, São Carlos, Brazil.
authors: Audrey
authors: A
authors: Borghi-Silva
mesh_terms: D000368:Aged; D001938:Brazil; D003430:Cross-Sectional Studies; D006321:Heart / Q000294:innervation*; D006339:Heart Rate; D006801:Humans; D016014:Linear Models; D008168:Lung / Q000503:physiopathology*; D008176:Lung Volume Measurements; D008297:Male; D008875:Middle Aged; D008955:Models, Cardiovascular; D017711:Nonlinear Dynamics; D010275:Parasympathetic Nervous System / Q000503:physiopathology; D056888:Patient Positioning; D011237:Predictive Value of Tests; D011653:Pulmonary Diffusing Capacity; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D057185:Sedentary Behavior; D012720:Severity of Illness Index; D013147:Spirometry; D016683:Supine Position
keywords: COPD; cardiac autonomic nervous system; heart rate variability; lung diffusion capacity; rest hyperinflation; static lung volumes