Proximal and Distal Lung Mechanics in Antigen Challenged Allergic Cynomolgus Monkeys

Abstract

We used the forced oscillation technique (FOT) to measure impedance in the pulmonary system and the effects of antigen challenge on the proximal and distal lung. In addition, we treated animals with two oral doses of placebo or betamethasone (1 mg/kg) 18 and 2 hours prior to antigen challenge. FOT provides indices of proximal (Newtonian airway resistance RN) and distal airway status (tissue damping (G) and elastance (H)). Ascaris suum antigen challenge caused a significant increase in RN, G and H. Pretreatment with betamethasone significantly reduced the peak increase in RN and the area under the curve of the FOT response over 60 minutes. G and H responses were unaffected by steroid treatment. These data indicate that, using the FOT, we can dissociate the response of proximal and distal airways to an antigen challenge. Moreover, steroid pre‐treatment can reduce the bronchoconstrictor response to inhaled antigen but this effect is primarily via effects on proximal airways with little effect on the distal airways and parenchymal component of pulmonary impedance. These data may help to explain the apparent disconnect between the empirical and subjective measures of efficacy for some asthma treatments.