Airway cooling: stimulus specific modulation of airway responsiveness in the canine lung periphery.

We used a wedged bronchoscope technique in conjunction with an in situ isolated perfused left lower lobe preparation in anesthetized dogs to examine cold-associated airway modulation of peripheral lung responses to dry airflow, hypocapnia, and aerosols of histamine and hypertonic NaCl. In this preparation, airway wall temperature was rapidly lowered by decreasing the temperature of blood perfusing the wedged sublobar segment. Cooling significantly attenuated responses to dry air, hypertonic NaCl aerosol, and hypocapnic challenge. In contrast, cooling did not affect peripheral lung responses to aerosolized histamine. Thus, cooling per se does not inhibit the responsiveness of smooth muscle. We conclude that, depending on the stimulus, cooling can modulate airway reactivity. We speculate that cooling attenuates hypocapnia, hypertonic aerosol, and dry air-induced bronchospasm via a cold induced reduction in neuronal activity or mediator production and release.