Intraairway thermal profiles during exercise and hyperventilation in normal man.

Area of Science:

• Physiology
• Respiratory System
• Thermoregulation

Background:

• Inhaling large volumes of air rapidly involves the tracheobronchial tree in conditioning.
• Inspired air may not reach body temperature and humidity until deep within the lungs.

Purpose of the Study:

• To investigate if the method of elevating ventilation affects airway temperature during cold air inhalation.
• To compare thermal responses during exercise-induced hyperpnea versus voluntary hyperventilation.

Main Methods:

• Seven healthy subjects inhaled frigid air during 5 minutes of either exercise or voluntary hyperventilation.
• Airstream temperature was measured at six points in the tracheobronchial tree.
• Minute ventilation, respiratory frequency, and intrathoracic temperatures were recorded.

Main Results:

• Both exercise and voluntary hyperventilation caused dramatic drops in airway temperature.
• No significant differences in temperature changes were observed between the two ventilation methods.
• Airstream temperature did not increase during exercise.

Conclusions:

• Voluntary hyperventilation can simulate the thermal events of moderate exercise in the lungs when ventilation and air conditions are matched.
• Bronchial blood supply might be influenced by local airway thermal recovery needs, potentially independent of cardiac output increases.