Intra-airway thermodynamics during exercise and hyperventilation in asthmatics.

To determine whether exercise and hyperventilation produce the same intrathoracic thermal events in asthmatics, we used a thermal probe to record airstream temperatures during both stimuli at multiple points within the tracheobronchial tree. From these data, the global and regionally distributed exchanges of water and heat that occurred throughout the respiratory tract were calculated. During each provocation, intra-airway temperatures fell equivalently, thereby producing similar intrathoracic water fluxes and heat transfers. Neither stimulus was associated with airway drying, and both resulted in similar distributed losses of thermal energy from the tracheobronchial tree despite small regional heat and water exchanges. The degree of airway obstruction was identical after both challenges; however, the onset of airway narrowing was earlier with hyperventilation and developed in association with more rapid rewarming. These data demonstrate that the hyperpnea of exercise and hyperventilation produce identical thermal consequences within the respiratory tract of asthmatics.