The Role of Respiratory Heat Exchange in the Production of Exercise-Induced Asthma.

摘要

By having our subjects inhale dry air at various temperatures ranging from subzero to 80 C in a random fashion, the authors have tested the hypothesis that it is the total heat flux in the tracheobronchial tree during exercise that determines the degree of post-exertional obstruction that develops in asthma. The authors purpose in this was to determine if heat could be transferred from the air to the mucosa so as to offset evaporative losses from the airways. The observed responses breathing completely dry air fell as the temperature was increased and exactly matched theoretical predictions over a range of inspired air temperatures from -11 to 37 C. Above 37 C the observed response exceeded predictions, indicating that it was not possible to provide sufficient heat per se in the air to offset the vaporization of water. However, when small amounts of water were added to the inspirate at high temperatures, bronchospasm was virtually abolished and the response again closely matched theorecal exexpectations. The authors conclude that the magnitude of exercise induced asthma is directly proportional to the thermal load placed upon the airways and that this reaction is quantifiable in terms of respiratory heat exchange.