APStracts 6:0257A, 1999.

Airway obstruction during exercise and isocapnic hyperventilation in asthmatics. Suman, Oscar E., Kenneth C. Beck, Mark A. Babcock, David F. Pegelow, and William G. Reddan. 1Thoracic Diseases Research Unit, Division of Pulmonary & Critical Care Medicine, Mayo Clinic, Rochester, MN 55905 USA and 2John Rankin Laboratory of Pulmonary Medicine, Departments of Preventive Medicine and Medicine, The University of Wisconsin, Madison, WI 53705, USA

APStracts 6:0257A, 1999.

We compared pulmonary mechanics measured during long-term exercise (LTX = 20 minutes) with long-term isocapnic hyperventilation (LTIH = 20 minutes) in the same asthmatic individuals (n=6). Peak expiratory flow (PEF) and forced expiratory volume in one second (FEV1) decreased during LTX (-19.7% and -22.0%, respectively) and during LTIH (-6.66% and 10.9%, respectively. In contrast, inspiratory pulmonary resistance (RLi) was elevated during LTX (57.6%) but not during LTIH (9.62%). Airway function deteriorated post-LTX and post -LTIH as expected (FEV1 = -30.2% and -21.2%; RLi = 111.8% and 86.5%, respectively). We conclude that the degree of airway obstruction observed during LTX is of a greater magnitude than that observed during LTIH. Both modes of hyperpnea induced similar levels of airway obstruction in the post-hyperpnea period. However, the greater airway obstruction obstruction during LTX suggests that a different process may be responsible for the changes in airway function during and after the two modes of hyperpnea. This finding raises questions about the equivalency of long-term isocapnic hyperventilation and long-term exercise in the study of airway function during exercise-induced asthma.

Received 9 October 1998; accepted in final form 27 May 1999.
APS Manuscript Number A910-8.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1999 The American Physiological Society.
Published in APStracts on 14 June 1999