Forced noise mechanical parameters during inspiration and expiration

Using the forced random noise technique we collected three 5-min records of pressure and flow signals in five clinically normal nonsmoking adults. Each recording was analyzed to obtain respiratory impedance spectra from data obtained during continuous sampling, midinspiration, and midexpiration. Estimates of respiratory resistance, inertance, and compliance were obtained by regression analysis on each impedance spectrum. Mean expiratory resistance and compliance were significantly (P less than 0.01) greater than corresponding mean inspiratory values, while mean expiratory inertance was significantly (P less than 0.001) less than the mean inspiratory value. Parameters from continuous sampling agreed fairly well with inspiratory resistance and inertance and with expiratory compliance. The coefficient of variation of parameters from continuous data were similar to, or smaller than, those from inspiratory or expiratory data. Thus continuous sampling appears to be an acceptable approach for collecting random noise data.