Effect of Disodium Cromoglycate on Ventilation and Gas Exchange During Exercise in Asthmatic Children With a Postexertion FEVi Fall Less Than 15 Percent: Conclusion
Although the mean postexercise fall in FEVi (5.9 percent) was significantly higher under untreated conditions, it was within the physiologic range for normal individuals. Furthermore, according to the current guidelines of asthma care, this drop in lung function is not considered clinically relevant and therefore premedication is not usually recommended. Contraceptive pills website In addition, the difference in the percentage of fall in FEVi and the difference in VEmax between the two tests were not related, suggesting that the modifications of pos-texertional airflow are not associated with the ventilatory adjustments during exercise. In other words, a fall in FEVi less than 15 percent from the baseline— the accepted cutoff to detect EIA—does not exclude an impairment of acute physiologic response to exercise in terms of greater ventilatory work load and O2 cost of breathing, as we found in these children when evaluated without premedication.
In the presence of airway obstruction, the flow limitation and the higher pulmonary volume can account for the greater Ve and oxygen cost of breathing during exercise, and so the prevention of airway caliber reduction seems to be a major mechanism to improve gas exchange. Other pathophysiologic mechanisms, however, should be involved in asymptomatic asthmatic subjects, like our patients, in whom a substantial FEVi fall did not occur.
The involvement of small airways may be suggested by the reduction of FEF25-75% in test without premedication (Table 1). Due to the great variability of this measurement, there was no statistically significant difference between the postexercise FEF25-75% in the two tests. Nevertheless, it is possible that this variability has masked changes in the more peripheral part of the bronchial tree. In effect, abnormal airway responses, such as dynamic changes in the bronchomotor tone and alterations of alveolar ventilation to perfusion matching, have been described during exercise even in asymptomatic asthmatic subjects with normal tests of airway function.’’