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Bronchial responsiveness to histamine after repeated exercise-induced bronchospasm
L P Boulet1, C Legris, H Turcotte
1Centre de Pneumologie, Hôpital Laval, Sainte-Foy, Qué., Canada.
Respiration; International Review of Thoracic Diseases
|January 1, 1987
Summary
Repeated exercise does not alter bronchial responsiveness in asthma patients. However, some individuals develop tachyphylaxis to histamine after multiple inhalations, independent of exercise.
Area of Science:
- Respiratory Medicine
- Exercise Physiology
Background:
- Asthma is characterized by bronchial hyperresponsiveness.
- Exercise can trigger bronchospasm, but its effect on subsequent responsiveness is unclear.
Purpose of the Study:
- To investigate the impact of repeated exercise-induced bronchospasm on nonspecific bronchial responsiveness (NSBR) to histamine.
- To determine if exercise-induced refractoriness affects NSBR.
Main Methods:
- 12 asthma patients underwent repeated histamine inhalation tests (HIT) and ergometer exercises.
- Nonspecific bronchial responsiveness was assessed by the provocative concentration of histamine causing a 20% fall in FEV1 (PC20).
- Control day involved only HIT; exercise day included HIT before and after three consecutive exercises.
Main Results:
- Repeated exercise did not significantly alter NSBR to histamine.
- A refractory period was observed in some subjects after the second exercise, without changes in histamine responsiveness.
- A significant reduction in histamine responsiveness (tachyphylaxis) occurred with repeated HIT on the control day.
Conclusions:
- Repeated exercise does not modify nonspecific bronchial responsiveness in asthmatics.
- Exercise-induced refractoriness is not mediated by changes in NSBR.
- Repeated histamine inhalation can lead to tachyphylaxis in some individuals.