title: The Relation of Respiratory Muscle Strength to Disease Severity and Abnormal Ventilation During Exercise in Chronic Heart Failure Patients.
abstract: BACKGROUND
  Breathlessness is a common problem in chronic heart failure (CHF) patients, and respiratory muscle strength has been proposed to play an important role in causing breathlessness in these patients.
  
  
  OBJECTIVE
  The aim of this study was to investigate the relation between respiratory muscle strength and the severity of CHF, and the influence of respiratory muscle strength on abnormal ventilation during exercise in CHF patients.
  
  
  METHODS
  In this case series study, we assessed clinically stable CHF outpatients (N = 66, age: 57.7 ± 14.6 years). The peak oxygen consumption (peak VO2), the slope relating minute ventilation to carbon dioxide production (VE/VCO2 slope), and the slope relating tidal volume to respiratory rate (TV/RR slope) were measured during cardiopulmonary exercise testing. Respiratory muscle strength was assessed by measuring the maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP).
  
  
  RESULTS
  The MIP and MEP decreased significantly as the New York Heart Association functional class increased (MIP, P = 0.021; MEP, P < 0.01). The MIP correlated with the TV/RR slope (r = 0.57, P < 0.001) and the VE/VCO2 slope (r = -0.44, P < 0.001), and the MEP also correlated with the TV/RR slope (r = 0.53, P < 0.001) and the VE/VCO2 slope (r = -0.25, P < 0.040). Stepwise multiple regression analysis revealed that age and MIP were statistically significant predictors of the TV/RR and VE/VCO2 slopes (both P < 0.05).
  
  
  CONCLUSIONS
  Respiratory muscle strength is related to the severity of CHF, and associated with rapid and shallow ventilation or excessive ventilation during exercise.
authors.affiliation: Department of Rehabilitation Medicine, St. Marianna University School of Medicine, Yokohama City Seibu Hospital, Yokohama, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kasahara
authors.affiliation: Graduate School of Health Sciences, Kobe University, Kobe, Japan.
authors.forename: Kazuhiro P
authors.initials: KP
authors.lastname: Izawa
authors.affiliation: Department of Rehabilitation Medicine St. Marianna University School of Medicine Hospital, Kawasaki, Japan.
authors.forename: Satoshi
authors.initials: S
authors.lastname: Watanabe
authors.affiliation: Division of Cardiology, St. Marianna University School of Medicine Toyoko Hospital, Kawasaki, Japan.
authors.forename: Naohiko
authors.initials: N
authors.lastname: Osada
authors.affiliation: Division of Cardiology, Department of Internal Medicine (NO, KO), St. Marianna University School of Medicine, Yokohama City Seibu Hospital, Yokohama, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Omiya
keywords: Exercise Test; Heart Failure; Respiratory Muscle