Harris R Scott, Winkler Tilo, Tgavalekos Nora, Musch Guido, Melo Marcos F Vidal, Schroeder Tobias, Chang Yuchiao, Venegas José G
Department of Medicine (Pulmonary and Critical Care Unit and General Medicine Unit), Massachusetts General Hospital and Harvard Medical School, Boston, MA 02114, USA.
Am J Respir Crit Care Med. 2006 Aug 1;174(3):245-53. doi: 10.1164/rccm.200510-1634OC. Epub 2006 May 11.
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.
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).
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.
During methacholine-induced bronchoconstriction, perfusion to ventilation defects are systematically reduced by a relative increase in regional pulmonary vascular resistance.
哮喘中的支气管收缩会导致通气不均一，并在肺部形成大的、连续的通气缺陷。然而，肺灌注（Q）对这种通气缺陷的区域适应性尚未得到充分研究。
我们使用正电子发射断层扫描来评估静脉注射示踪剂氮-13（13NN）的肺内动力学，并测量了11例轻度哮喘患者的通气和灌注区域分布。对于每个受试者，分析了在乙酰甲胆碱诱导的支气管收缩之前和期间13NN的区域洗脱动力学。定义了两个感兴趣区域（ROI）：一个位于支气管收缩期间示踪剂保留（TR）较高的空间连续区域上，另一个覆盖大小相似、示踪剂保留（NR）最小的区域。
两个ROI均显示出不均一的洗脱动力学，可用具有快速和慢速洗脱速率的两室模型来描述。我们发现支气管收缩期间TR ROI的区域Q系统性降低，而NR区域的相对Q变化不定且无显著意义。区域Q的降低与TR ROI的区域气体含量增加有关，但其幅度大于仅由区域肺膨胀变化所预期的幅度。
在乙酰甲胆碱诱导的支气管收缩期间，区域肺血管阻力相对增加会系统性地减少对通气缺陷区域的灌注。
