Tracheal mucociliary transport in experimental canine asthma

The effect of experimental asthma on tracheal mucous velocity (TMV) was investigated in anesthetized mongrel dogs. Ten dogs were exposed to an aerosol of Ascaris suum Antigen (AA) in a 1:1000 dilution, whereas 8 controls with skin reactivity to AA but not to ragweed extract inhaled a 1:100 dilution of the latter. Respiratory system conductance (Grs), static lung compliance (CL) and TMV employing a cinebronchofiberscopic technique were determined before and serially following aerosol exposure. Five of the 10 AA exposed dogs responded with a significant decrease in Grs (-78%) and CL (-23%) after 5 min (reactors), whereas the remaining 5 AA exposed dogs (non reactors) and the controls showed no changes in these parameters. Mean TMV decreased significantly with 30 min in both the reactors (-58%) and non reactors (-65%) and remained low until the end of the 2 hr observation period at which time respiratory mechanics had returned to baseline values. No changes in TMV were observed in the controls. Aerosols of acetylcholine and histamine in concentrations which simulated the mechanical response observed following AA inhalation, increased or did not change TMV. These results indicate that experimental asthma in the dog is associated with a rapid and sustained impairment of TMV which appears to be independent of the development of bronchospasm.