The augmented RIC model of the human respiratory system.

This paper describes the augmented RIC model of respiratory impedance and analyzes its parameter values estimated--by a modified Newton method with least squares criterion--from impulse oscillometry data. The data were from asthmatic children, tested pre- and post-bronchodilator, and from healthy adults and a second group of adults with COPD. Our analyses show that the augmented RIC model was 13.7-66.6% more accurate than the extended RIC model at fitting these data, while its parameter estimates were within previously reported ranges, unlike the Mead 1969, DuBois and Mead models, which typically yielded compliance estimates exceeding 200 l/kPa. Additionally, the augmented RIC model's C(p) parameter, representing peripheral airway compliance, is a statistically significant discriminator between unconstricted and constricted conditions (with p < 0.001) occurring in asthma and COPD. This corresponds well with current medical understanding, so the augmented RIC model is potentially useful for detection and treatment of airflow obstruction.