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Bronchoconstriction in asthmatics exposed to sulfur dioxide during repeated exercise
Journal of Applied Physiology (Bethesda, Md. : 1985)
|September 1, 1985
Summary
Mild asthmatics experienced significant bronchoconstriction when exercising in sulfur dioxide (SO2) at 0.5 and 1.0 ppm. Repeated exercise reduced this SO2-induced airway narrowing, suggesting a protective effect in asthma patients.
Area of Science:
- Environmental Health
- Pulmonary Medicine
- Toxicology
Background:
- Sulfur dioxide (SO2) is a common air pollutant.
- Asthma patients exhibit heightened airway sensitivity to irritants.
- Exercise can exacerbate asthma symptoms.
Purpose of the Study:
- To investigate the effects of short-term sulfur dioxide (SO2) exposure during exercise on airway resistance in mild asthmatics.
- To determine if repeated exercise exposure alters the bronchoconstrictive response to SO2.
Main Methods:
- Young male volunteers with mild asthma and methacholine sensitivity were exposed to varying concentrations of SO2 (0.0, 0.25, 0.5, 1.0 ppm) during moderate treadmill exercise.
- Specific airway resistance (sRaw) and respiratory impedance were measured.
- Forced random noise was used to assess peripheral airway involvement.
Main Results:
- Significant increases in sRaw were observed at 0.5 and 1.0 ppm SO2, indicating dose-dependent bronchoconstriction.
- Bronchoconstriction was primarily linked to peripheral airways.
- The magnitude of SO2-induced airway narrowing decreased with repeated exercise bouts.
Conclusions:
- Mild asthmatics are susceptible to bronchoconstriction from moderate exercise in SO2 concentrations of 0.5 and 1.0 ppm.
- Repeated exercise may attenuate the airway response to SO2 in individuals with asthma.
- Peripheral airway involvement is a key feature of SO2-induced bronchoconstriction in this population.