title: Effects of acute changes in pulmonary wedge pressure on periodic breathing at rest in heart failure patients.
abstract: BACKGROUND
  Patients with heart failure (HF) display a number of breathing abnormalities including periodic breathing (PB) at rest. Although the mechanism(s) contributing to PB remain unclear, we examined whether changes in pulmonary wedge pressure (PWP) and pulmonary vascular resistance (PVR) alter PB in patients with established HF.
  
  
  METHODS
  We studied 12 male patients with HF (age, 50 +/- 11 years; ejection fraction, 18.3 +/- 3.8 %; New York Heart Association class, 3.2 +/- 0.4), with PB at rest, who are undergoing right heart catheterization with infusion of nitroprusside.
  
  
  RESULTS
  At baseline, patients with HF displayed minute ventilation (V(E)) oscillations with amplitude of 5.5 +/- 2.7 L/min (57 +/- 34% of the average V(E)) and cycle length of 61 +/- 18 seconds. Cardiac index (CI), PVR, and mean PWP averaged 2.0 +/- 0.4 L min(-1) m(-2), 281.9 +/- 214.9 dyne/s per cm(-5), and 28.3 +/- 5.4 mm Hg, respectively. During nitroprusside infusion, CI increased to 3.1 +/- 0.6 L min(-1) m(-2), PVR decreased to 163.9 +/- 85.2 dyne/s per cm(-5), and PWP fell to 10.0 +/- 4.2 mm Hg. Nitroprusside reduced the amplitude (2.6 +/- 2.4 L/min, 23 +/- 21% of average V(E); P < .01) and cycle length (41.4 +/- 28.8 seconds; P < .01) of V(E) oscillations while abolishing oscillations in 3 patients. Although average V(E) and PaCO2 remained unchanged, there was a significant increase in the ratio of tidal volume to inspiratory time (V(T)/T(I); P < .01), suggesting an increase in ventilatory drive. The change in the amplitude of V(E) oscillations was positively correlated with the change in PWP (r = 0.75; P < .01), negatively correlated with the change in PVR (r = 0.63; P < .05), and not correlated with the change in CI.
  
  
  CONCLUSIONS
  These data suggest that PWP (left atrial pressure) may play a direct role in the PB observed in HF at rest.
authors.affiliation: Mayo Clinic, College of Medicine, Rochester, MN 55905, USA.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Olson
authors.forename: Robert P
authors.initials: RP
authors.lastname: Frantz
authors.forename: Eric M
authors.initials: EM
authors.lastname: Snyder
authors.forename: Kathy A
authors.initials: KA
authors.lastname: O'Malley
authors.forename: Kenneth C
authors.initials: KC
authors.lastname: Beck
authors.forename: Bruce D
authors.initials: BD
authors.lastname: Johnson
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D006328:Cardiac Catheterization; D002302:Cardiac Output; D006333:Heart Failure / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009599:Nitroprusside / Q000494:pharmacology*; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D011659:Pulmonary Gas Exchange; D011669:Pulmonary Wedge Pressure / Q000187:drug effects*; D012119:Respiration / Q000187:drug effects*; D014655:Vascular Resistance / Q000187:drug effects; D014665:Vasodilator Agents / Q000494:pharmacology*
chemical_list: D014665:Vasodilator Agents; D009599:Nitroprusside; D010100:Oxygen