title: Regional pulmonary perfusion, inflation, and ventilation defects in bronchoconstricted patients with asthma.
abstract: BACKGROUND
  Bronchoconstriction in asthma leads to heterogeneous ventilation and the formation of large and contiguous ventilation defects in the lungs. However, the regional adaptations of pulmonary perfusion (Q) to such ventilation defects have not been well studied.
  
  
  METHODS
  We used positron emission tomography to assess the intrapulmonary kinetics of intravenously infused tracer nitrogen-13 ((13)NN), and measured the regional distributions of ventilation and perfusion in 11 patients with mild asthma. For each subject, the regional washout kinetics of (13)NN before and during methacholine-induced bronchoconstriction were analyzed. Two regions of interest (ROIs) were defined: one over a spatially contiguous area of high tracer retention (TR) during bronchoconstriction and a second one covering an area of similar size, showing minimal tracer retention (NR).
  
  
  RESULTS
  Both ROIs demonstrated heterogeneous washout kinetics, which could be described by a two-compartment model with fast and slow washout rates. We found a systematic reduction in regional Q to the TR ROI during bronchoconstriction and a variable and nonsignificant change in relative Q for NR regions. The reduction in regional Q was associated with an increase in regional gas content of the TR ROI, but its magnitude was greater than that anticipated solely by the change in regional lung inflation.
  
  
  CONCLUSIONS
  During methacholine-induced bronchoconstriction, perfusion to ventilation defects are systematically reduced by a relative increase in regional pulmonary vascular resistance.
authors.affiliation: Department of Medicine (Pulmonary and Critical Care Unit and General Medicine Unit), Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA. rharris@partners.org
authors.forename: R Scott
authors.initials: RS
authors.lastname: Harris
authors.forename: Tilo
authors.initials: T
authors.lastname: Winkler
authors.forename: Nora
authors.initials: N
authors.lastname: Tgavalekos
authors.forename: Guido
authors.initials: G
authors.lastname: Musch
authors.forename: Marcos F Vidal
authors.initials: MF
authors.lastname: Melo
authors.forename: Tobias
authors.initials: T
authors.lastname: Schroeder
authors.forename: Yuchiao
authors.initials: Y
authors.lastname: Chang
authors.forename: José G
authors.initials: JG
authors.lastname: Venegas
mesh_terms: D000328:Adult; D001249:Asthma / Q000378:metabolism / Q000503:physiopathology*; D016084:Bronchoconstriction / Q000502:physiology*; D016085:Bronchoconstrictor Agents / Q000008:administration & dosage; D005260:Female; D006801:Humans; D008297:Male; D016210:Methacholine Chloride / Q000008:administration & dosage; D009590:Nitrogen Radioisotopes / Q000493:pharmacokinetics*; D049268:Positron-Emission Tomography; D011652:Pulmonary Circulation / Q000502:physiology; D012123:Pulmonary Ventilation / Q000502:physiology*; D014692:Ventilation-Perfusion Ratio / Q000502:physiology
chemical_list: D016085:Bronchoconstrictor Agents; D009590:Nitrogen Radioisotopes; D016210:Methacholine Chloride