title: Expiratory loading improves cardiac output during exercise in heart failure.
abstract: OBJECTIVE
  The objective of this study was to investigate the effect of changes in expiratory intrathoracic pressure on stroke volume (SV) at rest and during moderate exercise in patients with heart failure versus healthy individuals.
  
  
  METHODS
  SV was obtained by echocardiography during spontaneous breathing and during expiratory loads of 5 and 10 cm H2O produced by a ventilator in 11 patients with heart failure (61 ± yr, ejection fraction: 32 ± 4%, New York Heart Association, 32% ± 4%; NYHA class I-II) and 11 age-matched healthy individuals at rest and during exercise at 60% of aerobic capacity on a semirecumbent cycle ergometer.
  
  
  RESULTS
  At rest, expiratory loading did not change HR, SV index (SVI), or cardiac index (CI) in either group. During moderate exercise, expiratory loading increased SVI and CI in patients with heart failure but decreased SVI and CI in healthy individuals. There was a negative correlation between changes in gastric pressure and SVI (r = -0.51, P < 0.05) in healthy individuals, whereas there was a positive correlation between changes in gastric pressure accompanying expiratory loading and CI (r = 0.83, P < 0.01) in patients with heart failure.
  
  
  CONCLUSIONS
  Expiratory loading during moderate exercise elicited increases in SVI and CI in patients with heart failure but decreased SVI and CI in healthy individuals. Improvements in cardiac function during submaximal exercise in patients with heart failure may be caused by a beneficial reduction in left ventricular preload.
authors: Division of Cardiovascular Diseases, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA. lalande.sophie@mayo.edu
authors: Sophie
authors: S
authors: Lalande
authors: Charles E
authors: CE
authors: Luoma
authors: Andrew D
authors: AD
authors: Miller
authors: Bruce D
authors: BD
authors: Johnson
mesh_terms: D000368:Aged; D000403:Airway Resistance / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology*; D016022:Case-Control Studies; D004452:Echocardiography; D015444:Exercise / Q000502:physiology*; D017079:Exercise Tolerance / Q000502:physiology; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006333:Heart Failure / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012146:Rest / Q000502:physiology; D013318:Stroke Volume / Q000502:physiology; D016277:Ventricular Function, Left / Q000502:physiology; D014939:Work of Breathing