Hyperpnea with dry air causes time-dependent alterations in mucosal morphology and bronchovascular permeability

This study examines the morphological and physiological changes that occur in canine peripheral airways after hyperpnea with dry air. Peripheral airways were exposed to a 5-min 2,000 ml/min dry air challenge (DAC) at 24, 6, 2, or 1 h before or 60 s after (0 h) the injection of colloidal carbon. After recording the dry air-induced increase in peripheral airway resistance, the lungs were removed and prepared for morphometric analysis (n = 5). Light microscopy revealed that 50% of the airway perimeter appeared damaged at 0, 1, and 2 h after DAC, and repair was evident 6-24 h after the challenge. The average goblet-to-ciliated cell ratio decreased from 0.34 before DAC to 0.15 after DAC and recovered within 24 h. Dry air-induced bronchovascular leakage occurred immediately after DAC and persisted for ≥24 h. DAC decreased mast cell number only in regions where the mucosa was damaged, and this decrease was inversely correlated with bronchovascular leakage. Finally, leukocyte infiltration was evident 1-2 h after DAC and continued throughout the 24-h period. We conclude that hyperpnea with dry air causes mucosal injury, inflammation, and microvascular leakage and that these dry air-induced effects persist for ≥24 h after DAC.