EFFECTS OF INCREASED BRONCHIAL BLOOD-FLOW ON AIRWAY MORPHOMETRY, RESISTANCE, AND REACTIVITY

It has been suggested that airway obstruction may be mediated in part by airway vascular engorgement or airway wall edema. However, there ar e few data that support this conjecture. In this study we examined the effects of increased bronchial blood flow (Qba) on airway wall dimens ions, conducting airway resistance, peripheral airway resistance, and airway reactivity assessed by methacholine aerosol challenge. The bron chial artery was perfused with autologous blood (control Qba = 0.6 ml. min(-1) kg(-1)) in anesthetized ventilated sheep. The artery was perfu sed at either control (C) Qba or at high (H) Qba (300% of C Qba) for 3 h. Morphometry showed a doubling of the vascular area in airways expo sed to H Qba (n = 4) compared with C Qba (n = 4). However, the signifi cant increase in wall area could be accounted for only partially by th e vascular changes, with edema fluid accumulation accounting for the m ajor increase. Despite these changes, baseline airway resistance (n = 16) and peripheral airway resistance were both unaltered. Airway react ivity to methacholine before and after H Qba was also examined (n = 12 ). The 3 h of H Qba had no effect on airway reactivity regardless of w hether challenge occurred with C or H Qba. The lack of effect-of vascu lar engorgement on airway resistance or reactivity does not support a primary role for these factors in mediating airway obstruction.