Elsevier

Respiratory Medicine

Volume 90, Issue 3, March 1996, Pages 145-151
Respiratory Medicine

Original article
Hyperventilation during exercise: independence on exercise-induced bronchoconstriction in mild asthma

https://doi.org/10.1016/S0954-6111(96)90156-0Get rights and content
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Abstract

Ventilatory gas exchange during exercise was compared in patients with mild asthma (11 females and 11 males), hyperventilation syndrome (HVS, 11 females), and healthy subjects (11 females and 11 males) in order to assess hyperventilation during exercise and its association with exercise-induced bronchoconstriction. The asthmatics showed decreased working capacity and decreased maximal oxygen consumption, with no evidence of limitation due to impairment of ventilatory capacity. Ventilatory equivalents for CO2 and O2 (V̇EV̇CO2 and V̇EV̇O2) at rest did not differ between the controls and asthmatics, but they were significantly elevated in HVS. In female asthmatics, ventilatory equivalents during exercise were significantly (P<0·05) elevated compared with those of healthy subjects; in female controls, V̇EV̇CO2 was 30·1 ± 3·3 at low exercise and 27·4 ± 6·5 at maximal exercise. In female asthmatics, the corresponding figures were 34·9 ± 6·1 and 36·7 ± 5·3. Furthermore, V̇EV̇CO2 individually related to percent of maximal oxygen consumption (V̇O2 max) was significantly increased in female asthmatics both at low and high V̇O2. The highest ventilatory equivalents were obtained in HVS, 41·7 ± 6·7 and 43·9 ± 0·9, respectively. Significant exercise-induced bronchoconstriction (decrease of FEV1 >15%) was found in 50% of the asthmatics. The ventilatory equivalents did not correlate with exercise-induced changes in FEV1 (r2<0·3). Mild exercise-induced hyperventilation which was observed in mild female asthmatics, did not appear to be related to exercise-induced bronchoconstriction.

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