Effect of pretest temperature on aerosol penetration and clearance in donkeys.

Pretest temperature and humidity were correlated with tracheobronchial particle penetration and clearance data from donkeys housed in unheated outdoor facilities and tested after spending 1-2 h in a temperature- and humidity-controlled laboratory. The animals inhaled an inert insoluble radioisotope-labeled monodisperse aerosol for several minutes. Its retention was monitored continuously for 3 h by external gamma detection. Aerosol deposition pattern and bronchial clearance were linearly correlated with pretest outdoor temperature which ranged from -10 to 30 degrees C. The fraction depositing in the unciliated regions of the lung decreased 0.6% per degrees C drop in outdoor temperature. Overall bronchial transport decreased at least 1.5% per degrees C decrease. Multiple linear regression analysis and correction for the positive correlation between temperature and humidity left no significant residual humidity dependence. Acclimatization of the animals in the laboratory for 6 h before testing significantly reduced these effects.