title: High-Intensity Inspiratory Protocol Increases Heart Rate Variability in Myocardial Revascularization Patients.
abstract: OBJECTIVE
  To evaluate heart rate variability during an inspiratory muscle endurance protocol at three different load levels [30%, 60% and 80% of maximal inspiratory pressure], in patients who had previously undergone coronary artery bypass grafting.
  
  
  METHODS
  Nineteen late postoperative myocardial revascularization patients participating in a cardiovascular rehabilitation program were studied. Maximal inspiratory pressure maneuvers were performed. An inspiratory muscle endurance protocol at 30%, 60% and 80% of maximal inspiratory pressure was applied for four minutes each, in random order. Heart rate and RR intervals were recorded and heart rate variability was analyzed by time (RMSSD-the mean of the standard deviations for all R-R intervals, and RMSM-root-mean square differences of successive R-R intervals) and frequency domains indices (high and low frequency) in normalized units. ANOVA for repeated measurements was used to compare heart rate variability indices and Student t-test was used to compare the maximal inspiratory pressure and maximal expiratory pressure values.
  
  
  RESULTS
  Heart rate increased during performance of maximal respiratory pressures maneuvers, and the maximal inspiratory pressure and maximal expiratory pressure mean values were significantly lower than predicted values (P <0.05). RMSSD increased significantly at 80% in relation to rest and 30% of maximal inspiratory pressure and RMSM decreased at 30% and 60% of maximal inspiratory pressure in relation to rest (P <0.05). Additionally, there was significant and progressive decrease in low frequency and increase in high frequency at 30%, 60% and 80% of maximal inspiratory pressure in relation to the resting condition.
  
  
  CONCLUSIONS
  These results suggest that respiratory muscle training at high intensities can promote greater parasympathetic activity and it may confer important benefits during a rehabilitation program in post-coronary artery bypass grafting.
authors.affiliation: Laboratory of Cardiopulmonary Physiotherapy, Federal University of São Carlos, São Carlos, SP, Brazil.
authors.forename: Flavia Cristina Rossi
authors.initials: FC
authors.lastname: Caruso
authors.affiliation: Laboratory of Cardiopulmonary Physiotherapy, Federal University of São Carlos, São Carlos, SP, Brazil.
authors.forename: Rodrigo Polaquini
authors.initials: RP
authors.lastname: Simões
authors.affiliation: Department of Physiotherapy, Faculty of Medicine, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
authors.forename: Michel Silva
authors.initials: MS
authors.lastname: Reis
authors.affiliation: Department of Sciences of Human Movement, Federal University of São Paulo, Santos, SP, Brazil.
authors.forename: Solange
authors.initials: S
authors.lastname: Guizilini
authors.affiliation: Faculty of Medical Sciences at Santa Casa de São Paulo, São Paulo, SP, Brazil.
authors.forename: Vera Lucia dos Santos
authors.initials: VL
authors.lastname: Alves
authors.affiliation: Hospital São Francisco of Ribeirão Preto, Ribeirão Preto, SP, Brazil.
authors.forename: Valeria
authors.initials: V
authors.lastname: Papa
authors.affiliation: Department of Physical Therapy and Integrative Physiology Laboratory, College of Applied Health Sciences, University of Illinois Chicago, Chicago, IL, USA.
authors.forename: Ross
authors.initials: R
authors.lastname: Arena
authors.affiliation: Laboratory of Cardiopulmonary Physiotherapy, Federal University of São Carlos, São Carlos, SP, Brazil.
authors.forename: Audrey
authors.initials: A
authors.lastname: Borghi-Silva
mesh_terms: D000368:Aged; D000704:Analysis of Variance; D001945:Breathing Exercises / Q000379:methods*; D001026:Coronary Artery Bypass / Q000534:rehabilitation*; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D001239:Inhalation / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength / Q000502:physiology; D052580:Muscle Stretching Exercises / Q000379:methods*; D012016:Reference Values; D012129:Respiratory Function Tests; D012132:Respiratory Muscles / Q000503:physiopathology*; D012307:Risk Factors; D018709:Statistics, Nonparametric; D013997:Time Factors; D016896:Treatment Outcome