Noninvasive, quick obstruction estimation method for the measurement of parameters in the nonlinear lung model.

摘要

noninvasive technique for estimating lung model parameters was developed, implemented, and tested with in vitro and in vivo experiments. It estimates the dynamic properties of the lung: total (respiratory) resistance (linear and nonlinear), total compliance and total inertance. The calculation method was verified by estimating parameters from a model with known input properties. It was further supported with data from tests performed on a mechanical lung analog, the Training Test Lung.;The test procedure required obstructing the airflow while simultaneously recording flow and mouth pressure. The portion of the recorded signal during the momentary obstruction (difference between the response and the pre-excitation extrapolation) was extracted and fitted to the lung model using least squares curve fitting. Two separate obstructions were necessary to obtain all the lung parameters. The first obstruction was of long duration (150 ms) and produced compliance and resistance. The second obstruction was of short duration (45 ms) and was used with the compliance obtained earlier to produce resistance (again) and inertance.;Application to awake, normal, breathing subjects was accomplished by first using a conventional method for measuring compliance (weighted spirometer) since the long obstruction test did not yield satisfactory values. Apparently, most subjects were unable to relax their diaphragm during expiration. The spirometer compliance values were then used with the short duration obstruction response to obtain resistance and inertance. The test was performed on twenty male, nonsmoking subjects. Absolute values of measured total resistance were in agreement with a derived expression for total resistance obtained by modifying published airway resistance information. The derived equation was: R;Measured values of human lung inertance were slightly lower than an average theoretical calculation for the entire airway. The calculated value for a lung model was 1.03