Breathing pattern simulation using slit/cam valve.

A breathing simulator was developed to reproduce the human breathing pattern. The simulator incorporated a newly designed slit/cam valve without piston/cylinder or bellows. This breathing simulator was able to separate airflow into expiration and inspiration without check valves. The separation of flow facilitated easy and precise measurements of the aerosol or gas concentrations in performance tests of respirator filters, exhalation valves, and whole respirators under cyclic flow conditions. The programmed motions of the single cam of the slit/cam valve produced all the patterns of sedentary, 208, 415, and 622 kg.m/min work rates presented in other research because the stepping motor driving the cam was controlled by microcomputer and the breathing patterns were stored in the computer memory. The breathing patterns generated by this simulator were smooth curves and reproduced the original curves very precisely. The breathing simulator is very small and can be utilized for testing protective equipment.