title: Magnetic resonance imaging of uneven pulmonary perfusion in hypoxia in humans.
abstract: BACKGROUND
  Inhomogeneous hypoxic pulmonary vasoconstriction causing regional overperfusion and high capillary pressure is postulated for explaining how high pulmonary artery pressure leads to high-altitude pulmonary edema in susceptible (HAPE-S) individuals.
  
  
  OBJECTIVE
  Because different species of animals also show inhomogeneous hypoxic pulmonary vasoconstriction, we hypothesized that inhomogeneity of lung perfusion in general increases in hypoxia, but is more pronounced in HAPE-S. For best temporal and spatial resolution, regional pulmonary perfusion was assessed by dynamic contrast-enhanced magnetic resonance imaging.
  
  
  METHODS
  Dynamic contrast-enhanced magnetic resonance imaging and echocardiography were performed during normoxia and after 2 h of hypoxia (Fi(O2) = 0.12) in 11 HAPE-S individuals and 10 control subjects. As a measure for perfusion inhomogeneity, the coefficient of variation for two perfusion parameters (peak signal intensity, time-to-peak) was determined for the whole lung and isogravitational slices.
  
  
  RESULTS
  There were no differences in perfusion inhomogeneity between the groups in normoxia. In hypoxia, analysis of coefficients of variation indicated a greater inhomogeneity in all subjects, which was more pronounced in HAPE-S compared with control subjects. Discrimination between HAPE-S and control subjects was best in gravity-dependent lung areas. Pulmonary artery pressure during hypoxia increased from 22 +/- 3 to 53 +/- 9 mm Hg in HAPE-S and 24 +/- 4 to 33 +/- 6 mm Hg in control subjects (mean +/- SD; p < 0.001), respectively.
  
  
  CONCLUSIONS
  This study shows that hypoxic pulmonary vasoconstriction is inhomogeneous in hypoxia in humans, particularly in HAPE-S individuals where it is accompanied by a greater increase in pulmonary artery pressure compared with control subjects. These findings support the hypothesis of exaggerated and uneven hypoxic pulmonary vasoconstriction in HAPE-S individuals.
authors.affiliation: University Hospital Heidelberg, Internal Medicine VII, Sports Medicine, Im Neuenheimer Feld 410, D-69120 Heidelberg, Germany. christoph.dehnert@med.uni-heidelberg.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Dehnert
authors.forename: Frank
authors.initials: F
authors.lastname: Risse
authors.forename: Sebastian
authors.initials: S
authors.lastname: Ley
authors.forename: Tristan A
authors.initials: TA
authors.lastname: Kuder
authors.forename: Ralf
authors.initials: R
authors.lastname: Buhmann
authors.forename: Michael
authors.initials: M
authors.lastname: Puderbach
authors.forename: Elmar
authors.initials: E
authors.lastname: Menold
authors.forename: Derliz
authors.initials: D
authors.lastname: Mereles
authors.forename: Hans-Ulrich
authors.initials: HU
authors.lastname: Kauczor
authors.forename: Peter
authors.initials: P
authors.lastname: Bärtsch
authors.forename: Christian
authors.initials: C
authors.lastname: Fink
mesh_terms: D000328:Adult; D000531:Altitude; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008168:Lung / Q000098:blood supply; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D011651:Pulmonary Artery / Q000502:physiology; D011654:Pulmonary Edema / Q000503:physiopathology*; D014661:Vasoconstriction / Q000502:physiology*