Background The constant-phase model (CPM) is commonly fit to respiratory system input impedance (Zrs) to estimate lung mechanics. Driving signal frequencies and the method of model fitting may influence the results, especially in cases of severe lung disease or under severe bronchoconstriction. Objective To illustrate the effects of different CPM fits to Zrs data using a mouse model of influenza-induced lung disease. Methods BALB/c mice infected with influenza (or control) were challenged with methacholine. The CPM was fitted to Zrs, measured between 0·25 and 19·625Hz, using both unweighted and weighted fits. The effect of different lowest frequencies was assessed. Results and Conclusions For influenza-infected mice, the unweighted fit was poor, and airway resistance (Raw) was often biologically impossible. The weighted fit provided more realistic estimates of Raw. Different model fits and minimal frequencies had little effect on tissue mechanics.
- Constant-phase model
- Forced oscillation technique
- Severe lung disease
ASJC Scopus subject areas
- Pulmonary and Respiratory Medicine
- Public Health, Environmental and Occupational Health
- Infectious Diseases