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Bronchial Vascular Engorgement and Airflow Obstruction

1995; Elsevier BV; Volume: 107; Issue: 3 Linguagem: Inglês

10.1378/chest.107.3_supplement.103s

1931-3543

Elizabeth M. Wagner, Wayne Mitzner,

Respiratory Support and Mechanisms

Recent studies suggest a prominent role for the airway vasculature in causing airflow obstruction and enhanced reactivity in asthmatic subjects. Specifically, bronchial vascular engorgement has been proposed as a primary cause of airway narrowing in asthmatic subjects after exercise, in patients with left heart failure, and in experimental volume loading. To determine the extent of bronchial vascular engorgement and its effect on airway dimensions, we studied anesthetized, ventilated sheep in which the bronchial artery was cannulated and perfused with autologous blood (0.6 mL/min/kg). Morphometric measurements were made of small airways (<2 mm diameter) under control conditions and with vascular engorgement induced by the following: (1) high bronchial blood flow; (2) increased left atrial pressure (Pla; 15 to 20 mm Hg) produced by inflating a balloon-tip catheter in the left atrium; and (3) increased Pla with infusion of papaverine (pap) directly into the bronchial artery. The third protocol was performed to determine whether engorgement could cause airway narrowing when airway smooth muscle was completely relaxed. Lung tissue samples were acquired in vivo by double-clamping a lung lobe, rapidly cutting it free, and immersing it in liquid nitrogen. Samples were then processed for histologic sectioning. Airway and vascular dimensions of ten airways per animal were measured using a digitizing tablet. The results in Table 1 are presented with lumenal area as a percent of the maximally relaxed airway area and bronchial vascular area as a percent of the wall area. These results show that although bronchial vascular engorgement can lead to a slight decrease in lumenal area, this is not caused by passive mechanical forces. Rather, the engorgement leads to increased bronchial smooth muscle tone.Table 1Effects of Vascular EngorgementControlHigh FlowIncreased PlaIncreased Pla w/pap & ↑ Flow(n=4)(n=4)(n=4)(n=3)% Lumenal area84 ± 280 ± 276 ± 3*p<0.05, different from control.84 ± 1% Vascular area7 ± 113± 1*p<0.05, different from control.13 ± 1*p<0.05, different from control.13 ± 1*p<0.05, different from control.* p<0.05, different from control. Open table in a new tab