title: High-altitude pulmonary edema is initially caused by an increase in capillary pressure.
abstract: BACKGROUND
  High-altitude pulmonary edema (HAPE) is characterized by severe pulmonary hypertension and bronchoalveolar lavage fluid changes indicative of inflammation. It is not known, however, whether the primary event is an increase in pressure or an increase in permeability of the pulmonary capillaries.
  
  
  RESULTS
  We studied pulmonary hemodynamics, including capillary pressure determined by the occlusion method, and capillary permeability evaluated by the pulmonary transvascular escape of 67Ga-labeled transferrin, in 16 subjects with a previous HAPE and in 14 control subjects, first at low altitude (490 m) and then within the first 48 hours of ascent to a high-altitude laboratory (4559 m). The HAPE-susceptible subjects, compared with the control subjects, had an enhanced pulmonary vasoreactivity to inspiratory hypoxia at low altitude and higher mean pulmonary artery pressures (37 +/- 2 versus 26 +/- 1 mmHg, P<0.001) and pulmonary capillary pressures (19 +/- 1 versus 13 +/- 1 mmHg, P < 0.001) at high altitude. Nine of the susceptible subjects developed HAPE. All of them had a pulmonary capillary pressure >19 mm Hg (range 20 to 26 mmHg), whereas all 7 susceptible subjects without HAPE had a pulmonary capillary pressure < 19 mm Hg (range 14 to 18 mm Hg). The pulmonary transcapillary escape of radiolabeled transferrin increased slightly from low to high altitude in the HAPE-susceptible subjects but remained within the limits of normal and did not differ significantly from the control subjects.
  
  
  CONCLUSIONS
  HAPE is initially caused by an increase in pulmonary capillary pressure.
authors.affiliation: Department of Internal Medicine, UniversitätsSpital, Zürich, Switzerland. klinmax@usz.unizh.ch
authors.forename: M
authors.initials: M
authors.lastname: Maggiorini
authors.forename: C
authors.initials: C
authors.lastname: Mélot
authors.forename: S
authors.initials: S
authors.lastname: Pierre
authors.forename: F
authors.initials: F
authors.lastname: Pfeiffer
authors.forename: I
authors.initials: I
authors.lastname: Greve
authors.forename: C
authors.initials: C
authors.lastname: Sartori
authors.forename: M
authors.initials: M
authors.lastname: Lepori
authors.forename: M
authors.initials: M
authors.lastname: Hauser
authors.forename: U
authors.initials: U
authors.lastname: Scherrer
authors.forename: R
authors.initials: R
authors.lastname: Naeije
mesh_terms: D000328:Adult; D000531:Altitude; D001784:Blood Gas Analysis; D002196:Capillaries / Q000503:physiopathology*; D002199:Capillary Permeability; D006328:Cardiac Catheterization; D005260:Female; D005710:Gallium Radioisotopes; D006439:Hemodynamics; D006801:Humans; D006976:Hypertension, Pulmonary / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology; D000860:Hypoxia / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology; D008168:Lung / Q000098:blood supply* / Q000000981:diagnostic imaging / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D009942:Organometallic Compounds; D011652:Pulmonary Circulation; D011654:Pulmonary Edema / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology; D011669:Pulmonary Wedge Pressure; D013902:Radiography, Thoracic; D012016:Reference Values; D014168:Transferrin
chemical_list: D005710:Gallium Radioisotopes; D009942:Organometallic Compounds; D014168:Transferrin; C069724:gallium-transferrin complex