Mild isocapnic hypoxia enhances the bronchial response to methacholine in asthmatic subjects

Am Rev Respir Dis. 1988 Oct;138(4):789-93. doi: 10.1164/ajrccm/138.4.789.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Asthma / physiopathology*
  • Bronchi / drug effects*
  • Dose-Response Relationship, Drug
  • Female
  • Forced Expiratory Volume
  • Humans
  • Hypoxia / physiopathology*
  • Lung / physiopathology
  • Lung Compliance
  • Male
  • Methacholine Chloride
  • Methacholine Compounds / pharmacology*


  • Methacholine Compounds
  • Methacholine Chloride