The effect of repetitive exercise on airway temperatures

To determine if a relationship exists between intra-airway thermal events and the reduction in pulmonary mechanics that occur in asthmatics when they perform repetitive exercise, we recorded intrathoracic airstream temperatures in seven subjects during and after two identical bouts of cycle ergometry performed 30 min apart. From these data, global and regional thermal energy exchanges were calculated. Inspired air conditions, work loads, and minute ventilations were held constant for both trials. Pulmonary mechanics were measured prior to and serially after each challenge. As expected, the second provocation produced a smaller response than did the first. In association with these mechanical changes, the second challenge also produced less airway cooling and slower rewarming in the central airways. Hence, repetitive exercise trials performed over short intervals attenuate the essential thermal gradients necessary to produce obstruction. To the extent that these differences in intra-airway temperature reflect changes in perfusion, our data raise the possibility that the responsivity of the bronchial microcirculation of asthmatics may be altered by repetitive exercise.