Asthma diagnosis and treatment
Treatment of airway inflammation improves exercise pulmonary gas exchange and performance in asthmatic subjects

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Background

Asthma is an inflammatory disease of the airways that can lead to impaired arterial blood oxygenation during exercise.

Objective

We asked whether treatment of airway inflammation in asthmatic subjects would improve arterial blood gases during whole-body exercise.

Methods

By using a double-blind parallel-group design, 19 asthmatic subjects completed treadmill exercise to exhaustion on 2 occasions: (1) before and (2) after 6 weeks' treatment with an inhaled corticosteroid (ICS; n = 9) or placebo (n = 10).

Results

The ICS group had improved resting pulmonary function, decreased exercise-induced bronchospasm, and decreased postexercise sputum histamine during the posttreatment study compared with that during the pretreatment study. In the ICS group exercise Pao2 was significantly increased after treatment (84.8 to 93.8 mm Hg). Increased alveolar ventilation (arterial Pco2 decreased from 36.9 to 34.1 mm Hg) accounted for 37% of the increased Pao2 and improved gas exchange efficiency (alveolar-to-arterial Po2 difference decreased from 22.5 to 16.3 mm Hg) accounted for the remaining 63% of the increased Pao2 after treatment. In the ICS group exercise time to exhaustion was increased from 9.9 minutes during the pretreatment study to 14.8 minutes during the posttreatment study.

Conclusion

Treatment of airway inflammation in asthmatic subjects can improve arterial blood oxygenation during exercise by (1) improving airway function, thereby allowing increased alveolar ventilation during exercise, and (2) improving the efficiency of alveolar-to-arterial blood O2 exchange.

Clinical implications

In asthmatic patients ICSs not only attenuate exercise-induced bronchospasm but also improve arterial blood oxygenation during exercise.

Section snippets

Methods

See the Methods section in the Online Repository at www.jacionline.org for additional information.

Group characteristics

Descriptive characteristics and medications for the placebo and ICS groups are summarized in Table I. The 2 groups were similarly matched for all characteristics. Collectively, given the above average V˙o2max and the airway responses to inhaled β-agonist, exercise, and methacholine, we have classified the current group of subjects as being habitually active subjects with mild-to-moderate asthma.

Pulmonary function: Effects of treatment and exercise

Results for resting and postexercise lung function before and after treatment are summarized in Table

Summary of findings

The principal finding of this study was that asthmatic subjects treated with ICSs had significant improvements in arterial blood oxygenation during exercise. This improvement was related to increased alveolar ventilation (ie, decreased Paco2) and improved pulmonary gas exchange efficiency during the exercise (ie, decreased AaDo2). Furthermore, all but one subject in the ICS group was able to exercise longer after treatment; exercise time was increased by approximately 6.0 minutes (74%) in these

Conclusion

The results from this study show that treatment of airway inflammation in habitually active subjects with mild-to-moderate asthma can improve arterial blood oxygenation and exercise performance during whole-body exercise. This improvement is due to increased alveolar ventilation (caused by an increased maximal flow-volume loop) and improved pulmonary gas exchange efficiency (ie, decreased AaDo2). Thus in asthmatic subjects with modest levels of airway inflammation and mildly to moderately

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    Supported by National Heart, Lung, and Blood Institute grants RO1-HL015469 and T32-HL07654; Veterans Affairs/Department of Defense; and the Department of Pediatrics, University of Wisconsin–Madison.

    Disclosure of potential conflict of interest: H. C. Haverkamp, D. F. Pegelow, J. D. Miller, L. M. Romer, M. Santana, and M. W. Eldridge have received grant support from the National Heart, Lung, and Blood Institute; Veterans Affairs/Department of Defense; and the Department of Pediatrics, University of Wisconsin–Madison. J. A. Dempsey has declared that he has no conflict of interest.

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