Changes in tracheal mucosal thickness and blood flow in sheep

Airway narrowing may be produced by increasing the blood volume of the airway mucosa. Here changes in tracheal mucosal thickness (MT(tr)) were measured in 10 anesthetized sheep. Arteries to the cervical trachea were isolated, and blood flow (Q̇(tr)) was measured with an electromagnetic flow probe. Simultaneous changes in MT(tr) were measured with a mechanical probe over a fixed cartilage. Arterial injections of phenylephrine produced dose-related falls in Q̇(tr) and MT(tr) with a maximum peak fall in MT(tr) of -104 ± 18 (SE) μm. Methacholine, bradykinin, albuterol, and histamine produced dose-related increases in Q̇(tr). The largest peak increase in MT(tr) of 308 ± 121 μm was seen with bradykinin. For methacholine, albuterol, and histamine the largest increases in MT(tr) were 154 ± 47, 45 ± 10, and 153 ± 31 μm, respectively. The increases in MT(tr) were not always closely dose related. The peak changes in MT(tr) occurred substantially later than those in Q̇(tr) for all the drugs and up to 120 s later for methacholine and bradykinin. Generally, changes in MT(tr) and Q̇(tr) persisted for