Regional pulmonary perfusion, inflation, and ventilation defects in bronchoconstricted patients with asthma

R. Scott Harris, Tilo Winkler, Nora Tgavalekos, Guido Musch, Marcos F. Vidal Melo, Tobias Schroeder, Yuchiao Chang, José G. Venegas

Research output: Contribution to journalArticlepeer-review

92 Scopus citations


Rationale: 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 (Q̇ ) 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 ( 13NN), and measured the regional distributions of ventilation and perfusion in 11 patients with mild asthma. For each subject, the regional washout kinetics of 13NN 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 Q̇ to the TR ROI during bronchoconstriction and a variable and nonsignificant change in relative Q̇ for NR regions. The reduction in regional Q̇ 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. Conclusion: During methacholine-induced bronchoconstriction, perfusion to ventilation defects are systematically reduced by a relative increase in regional pulmonary vascular resistance.

Original languageEnglish
Pages (from-to)245-253
Number of pages9
JournalAmerican journal of respiratory and critical care medicine
Issue number3
StatePublished - Aug 1 2006
Externally publishedYes


  • Emission computed tomography
  • Pulmonary gas exchange
  • Vascular resistance
  • Vasoconstriction
  • Ventilation-perfusion ratio


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