title: Partitioning of pulmonary vascular resistance in primary pulmonary hypertension.
abstract: OBJECTIVE
  This study sought to determine the site of increased pulmonary vascular resistance (PVR) in primary pulmonary hypertension by standard bedside hemodynamic evaluation.
  
  
  BACKGROUND
  The measurement of pulmonary vascular pressures at several levels of flow (Q) allows the discrimination between active and passive, flow-dependent changes in mean pulmonary artery pressure (Ppa), and may detect the presence of an increased pulmonary vascular closing pressure. The determination of a capillary pressure (Pc') from the analysis of a Ppa decay curve after balloon occlusion allows the partitioning of PVR in an arterial and a (capillary + venous) segment. These approaches have not been reported in primary pulmonary hypertension.
  
  
  METHODS
  Ppa and Pc' were measured at baseline and after an increase in Q induced either by exercise or by an infusion of dobutamine, at a dosage up to 8 microg/kg body weight per min, in 11 patients with primary pulmonary hypertension. Reversibility of pulmonary hypertension was assessed by the inhalation of 20 ppm nitric oxide (NO), and, in 6 patients, by an infusion of prostacyclin.
  
  
  RESULTS
  At baseline, Ppa was 52+/-3 mm Hg (mean value+/-SE), Q 2.2+/-0.2 liters/min per m2, and Pc' 29+/-3 mm Hg. Dobutamine did not affect Pc' and allowed the calculation of an averaged extrapolated pressure intercept of Ppa/Q plots of 34 mm Hg. Inhaled NO had no effect. Prostacyclin decreased Pc' and PVR. Exercise increased Pc' to 40+/-3 mm Hg but did not affect PVR.
  
  
  CONCLUSIONS
  ns. These findings are compatible with a major increase of resistance and reactivity at the periphery of the pulmonary arterial tree.
authors.affiliation: Department of Intensive Care, Erasmus University Hospital, Brussels, Belgium.
authors.forename: S A
authors.initials: SA
authors.lastname: Kafi
authors.forename: C
authors.initials: C
authors.lastname: Mélot
authors.forename: J L
authors.initials: JL
authors.lastname: Vachiéry
authors.forename: S
authors.initials: S
authors.lastname: Brimioulle
authors.forename: R
authors.initials: R
authors.lastname: Naeije
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000328:Adult; D000368:Aged; D004280:Dobutamine / Q000494:pharmacology; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D006976:Hypertension, Pulmonary / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000502:physiology*; D011652:Pulmonary Circulation / Q000502:physiology*; D012039:Regional Blood Flow; D014655:Vascular Resistance
chemical_list: D000319:Adrenergic beta-Antagonists; D004280:Dobutamine