Mild isocapnic hypoxia enhances the bronchial response to methacholine in asthmatic subjects.
We studied the effect of mild isocapnic hypoxia (FIO2 = 15.5%) on lung mechanics, heart rate, circulating plasma catecholamines, and bronchial responsiveness to methacholine in ten asthmatic adults. Hypoxia did not alter lung mechanics (i.e., dynamic pulmonary compliance [CLdyn], pulmonary resistance [RL]) nor did it increase plasma catecholamines, but it significantly increased bronchial responsiveness to aerosolized methacholine, as assessed by the fall in forced expiratory volume in one second (FEV1: 1.2 +/- 0.18 versus 0.9 +/- 0.14 L/s, p less than 0.05), the rise in RL (RL: 19.1 +/- 1.4 versus 8.4 +/- 1 cm H2O/L/s, p less than 0.05), and the steeper slope of the dose-response curve to methacholine. We concluded that the hypoxic characteristic of asthmatic attacks may aggravate airflow obstruction.
Denjean
A
A
Laboratoire de Physiologie, Hôpital Antoine Béclère, Clamart, France.
Roux
C
C
Herve
P
P
Bonniot
J P
JP
Comoy
E
E
Duroux
P
P
Gaultier
C
C
D000328:Adult; D001249:Asthma / Q000503:physiopathology*; D001980:Bronchi / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D000860:Hypoxia / Q000503:physiopathology*; D008168:Lung / Q000503:physiopathology; D008170:Lung Compliance; D008297:Male; D016210:Methacholine Chloride; D008688:Methacholine Compounds / Q000494:pharmacology*
D008688:Methacholine Compounds; D016210:Methacholine Chloride