Computer-controlled flow resistance

A computer-controlled flow resistance (CCR), to be used in a computer-contr olled lung model, is presented. Flow is forced through a slit between a cyl inder and a sleeve around the cylinder. The resulting flow resistance depen ds on the width, circumferences and the variable length of the slit. The va riation in the length is computer-controlled by the position of the sleeve with respect to the cylinder. The total flow resistance also depends on inl et and outlet resistance at both sides of the slit and on flow. The depende nce on flow is primarily due to the shape of the inlet of the slit. The res istance of the slit itself is almost independent of flow. The resistance is calculated during a calibration phase at different positions of the sleeve , for flow values from 0.05 to 1.0 litre.s(-1) (inflow) and from -0.05 to - 1.0 litre.s(-1) (outflow). To simulate a required resistance pattern, as, f or instance, will occur during breathing, at each moment the set position o f the sleeve is calculated by means of an interpolation from the relationsh ip between flow resistance and position of the sleeve. The internal diamete r of the sleeve is fixed. To tune the resistance range for a specific simul ation, the cylinder is changed for one with different diameter, changing th e width of the slit.