Blood flow distribution within the airway wall

Area of Science:

• Pulmonary Physiology
• Respiratory Medicine
• Vascular Biology

Background:

• Bronchial blood flow, specifically perfusion of the mucosal and adventitial plexuses, is implicated in airway wall and lumen geometry.
• Understanding the distribution of bronchial perfusion is crucial for elucidating mechanisms of airway hyperresponsiveness.

Purpose of the Study:

• To investigate the distribution of bronchial perfusion in sheep.
• To determine the effect of altered perfusion on airway resistance (Raw) during methacholine chloride (MCh) challenge.

Main Methods:

• Utilized fluorescent microspheres to track bronchial perfusion distribution in sheep at baseline and during MCh challenge.
• Measured Raw in sheep during MCh challenge under conditions of normal and increased bronchial artery perfusion.

Main Results:

• Methacholine chloride challenge significantly increased Raw more with high than control perfusion.
• Microspheres predominantly lodged in the bronchial mucosa (60%), unaffected by MCh.
• Increased perfusion during MCh challenge led to greater microsphere deposition in larger airways (>1 mm) and less in smaller airways (<=1 mm) compared to control perfusion.

Conclusions:

• Regional differences in bronchial perfusion significantly influence agonist delivery to airway smooth muscle.
• Altered perfusion distribution, with greater delivery to larger airways and less to smaller airways under increased flow, explains observed changes in Raw during MCh challenge.
• Axial perfusion distribution is a key determinant of airway resistance during bronchoconstriction.