Airway resistance and tissue elastance from input or transfer impedance inbronchoconstricted monkeys

Ascaris suum (AS) challenge in nonhuman primates is used as an animal model of human asthma. The primary goal of this study was to determine whether t he airways and respiratory tissues in monkeys that are bronchoconstricted b y AS inhalation behave similarly to those in asthmatic humans. Airway resis tance (Raw) and tissue elastance (Eti) were estimated from respiratory syst em input (Zin) or transfer (Ztr) impedance. Zin (0.4-20 Hz) and Ztr (2-128 Hz) were measured in anesthetized cynomolgus monkeys (n = 10) under baselin e (BL) and post-AS challenge conditions. Our results indicate that AS chall enge in monkeys produces 1) predominately an increase in Raw and not tissue resistance, 2) airway wall shunting at higher AS doses, and 3) heterogeneo us airway constriction resulting in a decrease of lung parenchyma effective compliance. We investigated whether the airway and tissue properties estim ated from Zin and Ztr were similar and found that Raw estimated from Zin an d Ztr were correlated [r(2) = 0.76], not significantly different at BL (13. 6 +/- 1.4 and 13.1 +/- 0.9 cmH(2)O . l(-1) . s(-1), respectively), but sign ificantly different post-AS (20.5 +/- 4.5 cmH(2)O . l(-1) . s(-1) and 18.5 +/- 5.2 cmH(2)O . l(-1) . s(-1)). There was no correlation between Eti esti mated from Zin and Ztr. The changes in lung mechanical properties in AS-bro nchoconntricted monkeys are similar to those recently reported in human ast hma, confirming that this is a reasonable model of human asthma.