A respiration modulated air sampling pump

Abstract

A device was developed which controls the rate of operation of a portable personal air sampling pump proportional to the rate of inspiration of the wearer. The device was based on the relationship between thoracic impedance changes and pulmonary ventilation. The respiratory signal was detected using an impedance bridge, demodulated, filtered and amplified, and then converted to digital form for input into a microcomputer. The signal was processed further in digital form and reconverted into analog form were it was fed to the pump driver circuit. Operational evaluation of the impedance pneumographic controller (IPC) showed the expected variations in sensitivity and baseline from subject to subject, however, the linearity of the response was very consistent. The consistent linearity showed that the concept could be used in a device which could be easily calibrated, and when modified for portability, be used as a method for field use.