DEVELOPMENT OF A COMBINATION FORCED OSCILLATION - SPIROMETER DEVICE

Abstract

We developed a novel device, called the oscillation spirometer (OS) that can track changes in respiratory system impedance (Zrs) and can provide standard measures of respiratory resistance and spirometry. Current devices do not easily track temporal variation in Zrs. The device consists of a self-actuated piston containing an airflow resistance. During spirometry mode, the screen mesh pneumotachograph (PT) is stationary while during oscillation modes the PT translates generating oscillatory pressure. The actuator position is monitored continuously by a laser position sensing detector. To facilitate the design process, we developed a computer simulation of the actuator including mechanical and electromechanical compartments. A second model was created to simulate the patient Zrs and the two models were coupled and used to optimize design parameters such as magnet size, stroke volume, and piston cross-section, in a recursive design process. The result was a portable device with optimal stroke volume for expected patient loads. Three different designs were considered for the airflow resistance (orifice, groove and screen mesh resistances), and were tested using mock-up models. The final screen mesh resistance was linear, with a 98% lower 2nd order nonlinearity term than the next best design, and met American Thoracic Society standards. The OS could be used as a hand-held spirometer, or as a mounted FOT device suitable for detecting respiratory system resistance (Rrs) and its variation. It therefore has the potential to have a substantial impact in the respiratory market.