Are exercise and isocapnic voluntary hyperventilation identical bronchial provocations?

There is a positive and direct relationship between the magnitude of heat lost from the respiratory tract, the degree of cooling of intrathoracic airways and the magnitude of the airway obstructive response that develops in asthmatic subjects following exercise. We explore the possibilities of the causal nature of this relationship, the potential mechanisms by which they may relate and attempt to focus on the controversies that still exist with regard to the equivalency of respiratory heat loss (RHL) produced by exercise and by isocapnic voluntary hyperventilation (VHV) in asthmatics.