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ABSTRACT: 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 (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.Conclusion
During methacholine-induced bronchoconstriction, perfusion to ventilation defects are systematically reduced by a relative increase in regional pulmonary vascular resistance.
SUBMITTER: Harris RS
PROVIDER: S-EPMC2648114 | biostudies-literature | 2006 Aug
REPOSITORIES: biostudies-literature
Harris R Scott RS Winkler Tilo T Tgavalekos Nora N Musch Guido G Melo Marcos F Vidal MF Schroeder Tobias T Chang Yuchiao Y Venegas José G JG
American journal of respiratory and critical care medicine 20060511 3
<h4>Rationale</h4>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.<h4>Methods</h4>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 patie ...[more]