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  • Title: Pattern and mechanism of airway response to hypocapnia in normal subjects.
    Author: O'Cain CF, Hensley MJ, McFadden ER, Ingram RH.
    Journal: J Appl Physiol Respir Environ Exerc Physiol; 1979 Jul; 47(1):8-12. PubMed ID: 468677.
    Abstract:
    We examined the bronchoconstriction produced by airway hypocapnia in normal subjects. Maximal expiratory flow at 25% vital capacity on partial expiratory flow-volume (PEFV) curves fell during hypocapnia both on air and on an 80% helium- 20% oxygen mixture. Density dependence also fell, suggesting predominantly small airway constriction. The changes seen on PEFV curves were not found on maximal expiratory flow-volume curves, indicating the inhalation to total lung capacity substantially reversed the constriction. Pretreatment with a beta-sympathomimetic agent blocked the response, whereas atropine pretreatment did not, suggesting that hypocapnia affects airway smooth muscle directly, not via cholinergic efferents.
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