title: Bronchoarterial ratio on thin section CT: comparison between high altitude and sea level.
abstract: OBJECTIVE
  Our goal was to measure normal bronchial to accompanying pulmonary arterial diameter ratios and normal bronchial wall thickness on thin section CT at high altitude and at sea level.
  
  
  METHODS
  Seventeen normal, healthy, nonsmoking subjects living at 1,600 m altitude and 16 living at sea level underwent thin section CT (1.5 to 2.0 mm collimation). All images were photographed at window levels of -450 and -700 HU and window width of 1,500-1,600 HU. Internal diameters of the segmental and subsegmental bronchi were measured and compared with the diameter of the adjacent pulmonary artery. Bronchial wall thickness of each bronchus was measured. Only bronchi and arteries seen in cross section and within 1 mm from each other were included in the analysis.
  
  
  RESULTS
  Four hundred sixty-seven bronchi (215 at high altitude, 252 at sea level) were assessed. At window level of -450 HU, the bronchoarterial ratio was 0.76 +/- 0.14 (mean +/- SD) at altitude and 0.62 +/- 0.13 at sea level (p < 0.001). Bronchial wall thickness measured 0.92 +/- 0.09 mm (mean +/- SD) at altitude and 1.12 +/- 0.19 mm at sea level (p < 0.001). At window level of -700 HU, there was an artifactual decrease in the bronchoarterial diameter ratios and an increase in bronchial wall thickness.
  
  
  CONCLUSIONS
  Bronchoarterial ratio increases and bronchial wall thickness decreases with altitude. These findings are presumably related to hypoxic bronchodilatation and vasoconstriction.
authors.affiliation: Department of Radiology, University of British Columbia, Vancouver, Canada.
authors.forename: J S
authors.initials: JS
authors.lastname: Kim
authors.forename: N L
authors.initials: NL
authors.lastname: Müller
authors.forename: C S
authors.initials: CS
authors.lastname: Park
authors.forename: D A
authors.initials: DA
authors.lastname: Lynch
authors.forename: L S
authors.initials: LS
authors.lastname: Newman
authors.forename: P
authors.initials: P
authors.lastname: Grenier
authors.forename: C J
authors.initials: CJ
authors.lastname: Herold
mesh_terms: D000328:Adult; D000368:Aged; D000531:Altitude; D001995:Bronchography; D005260:Female; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008297:Male; D008875:Middle Aged; D011651:Pulmonary Artery / Q000000981:diagnostic imaging*; D012016:Reference Values; D014057:Tomography, X-Ray Computed