Show Summary Details
Page of

Understanding the relationship between atopic sensitization and airway hyper-responsiveness in asthma 

Understanding the relationship between atopic sensitization and airway hyper-responsiveness in asthma
Chapter:
Understanding the relationship between atopic sensitization and airway hyper-responsiveness in asthma
Author(s):

Todor A Popov

DOI:
10.1093/med/9780199651559.003.0053
Page of

PRINTED FROM OXFORD MEDICINE ONLINE (www.oxfordmedicine.com). © Oxford University Press, 2016. All Rights Reserved. Under the terms of the licence agreement, an individual user may print out a PDF of a single chapter of a title in Oxford Medicine Online for personal use (for details see Privacy Policy and Legal Notice).

date: 26 June 2019

Allergen-induced late asthmatic responses are associated with an increase in bronchial responsiveness to histamine. We have examined the relationship between the magnitude of the late asthmatic response and the magnitude and duration of increased histamine responsiveness. Allergen inhalation tests were carried out in 12 asthmatic subjects to induce a mild early asthmatic response (16% to 40% reduction in FEV1 in the first hour after allergen inhalation); the response was followed over 8 hr to identify the occurrence and magnitude of any late asthmatic response (maximum fall in FEV1 from baseline between 3 and 8 hr). The provocation concentration of histamine causing a decrease in FEV1 of 20% (PC20) was measured before and after inhalation of allergen. The magnitude of decrease in PC20 correlated with the magnitude of the late asthmatic response as measured by the percent fall in FEV1 (r = 0.8, p < 0.002). The duration of decrease in PC20 was from 2 to 74 days and this also correlated with the magnitude of the late response (r = 0.53, p < 0.05). Total lung capacity (TLC), residual volume (RV), FEV1, maximal expiratory flow-volume curves (on air and He-02), and histamine responsiveness were also measured before and at intervals after allergen inhalation. Four of seven subjects still had a reduction in PC20 when the TLC, RV, FEV1, maximal expiratory flow-volume rates on air (V50air) and He-02, (V50He-02) (measured at an absolute volume corresponding to control RV plus 50% of control vital capacity) and ratio of V50He-02 to V50 air were back to +10% of preallergen inhalation levels. In two of these subjects volume of isoflow was also back to ±10% of preallergen inhalation levels when the PC20 was still significantly reduced. The results suggest that allergen-induced late asthmatic responses can be associated with an increase in bronchial responsiveness to histamine by mechanisms other than a reduction in baseline airway caliber alone.

Access to the complete content on Oxford Medicine Online requires a subscription or purchase. Public users are able to search the site and view the abstracts for each book and chapter without a subscription.

Please subscribe or login to access full text content.

If you have purchased a print title that contains an access token, please see the token for information about how to register your code.

For questions on access or troubleshooting, please check our FAQs, and if you can't find the answer there, please contact us.