title: Airway obstruction during exercise and isocapnic hyperventilation in asthmatic subjects.
abstract: We compared pulmonary mechanics measured during long-term exercise (LTX = 20 min) with long-term isocapnic hyperventilation (LTIH = 20 min) in the same asthmatic individuals (n = 6). Peak expiratory flow (PEF) and forced expiratory volume in 1 s (FEV(1)) decreased during LTX (-19.7 and -22.0%, respectively) and during LTIH (-6.66 and 10. 9%, respectively). In contrast, inspiratory pulmonary resistance (RL(I)) was elevated during LTX (57.6%) but not during LTIH (9.62%). As expected, airway function deteriorated post-LTX and post-LTIH (FEV(1) = -30.2 and -21.2%; RL(I) = 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 posthyperpnea period. However, the greater airway 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 LTIH and LTX in the study of airway function during exercise-induced asthma.
authors.affiliation: Thoracic Diseases Research Unit, Division of Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, Minnesota 55905, USA. suman.oscar@mayo.edu
authors.forename: O E
authors.initials: OE
authors.lastname: Suman
authors.forename: K C
authors.initials: KC
authors.lastname: Beck
authors.forename: M A
authors.initials: MA
authors.lastname: Babcock
authors.forename: D F
authors.initials: DF
authors.lastname: Pegelow
authors.forename: A W
authors.initials: AW
authors.lastname: Reddan
mesh_terms: D000328:Adult; D000402:Airway Obstruction / Q000503:physiopathology*; D000465:Algorithms; D001250:Asthma, Exercise-Induced / Q000503:physiopathology*; D001831:Body Temperature / Q000502:physiology; D002245:Carbon Dioxide / Q000097:blood*; D015444:Exercise / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D015656:Respiratory Mechanics / Q000502:physiology; D014797:Vital Capacity
chemical_list: D002245:Carbon Dioxide