title: Proximal pulmonary artery blood flow characteristics in healthy subjects measured in an upright posture using MRI: the effects of exercise and age.
abstract: OBJECTIVE
  To use MRI to quantify blood flow conditions in the proximal pulmonary arteries of healthy children and adults at rest and during exercise in an upright posture.
  
  
  METHODS
  Cine phase-contrast MRI was used to calculate mean flow and reverse flow index (RFI) in the main (MPA), right (RPA), and left (LPA) pulmonary arteries in healthy children and adults in an open-MRI magnet equipped with an upright MRI-compatible ergometer.
  
  
  RESULTS
  From rest to exercise (150% resting heart rate), blood flow (liters/minute/m2) increased in the RPA (1.4+/-0.3 vs. 2.5+/-0.4; P<0.001), LPA (1.1+/-0.3 vs. 2.2+/-0.6; P<0.001), and MPA (2.7+/-0.5 vs. 4.9+/-0.5; P<0.001). RFI decreased in the LPA (0.040+/-0.030 vs. 0.017+/-0.018; P<0.02) and MPA (0.025+/-0.024 vs. 0.008+/-0.007; P<0.03). Adults experienced greater retrograde flow in the MPA than the children (0.042+/-0.029 vs. 0.014+/-0.012; P<0.02).
  
  
  CONCLUSIONS
  It appears that at both rest and during exercise, in children and adults alike, RPA/LPA mean blood flow distribution is predominantly determined by distal vascular resistance, while retrograde flow is affected by proximal pulmonary bifurcation geometry.
authors.affiliation: Department of Mechanical Engineering, Stanford University, Stanford, California 94305-4038, USA. cpc@stanford.edu
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Cheng
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Herfkens
authors.forename: Charles A
authors.initials: CA
authors.lastname: Taylor
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Feinstein
mesh_terms: D000293:Adolescent; D000328:Adult; D001642:Bicycling / Q000502:physiology; D001783:Blood Flow Velocity / Q000502:physiology; D002648:Child; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D019028:Magnetic Resonance Imaging, Cine / Q000379:methods*; D008297:Male; D011187:Posture / Q000502:physiology*; D011651:Pulmonary Artery / Q000502:physiology*