Portable forced oscillation device for point-of-care pulmonary function testing
Master of Science
The forced oscillation technique (FOT) provides a simple and accurate approach for pulmonary function testing. It minimizes patient cooperation by measuring the passive response of the respiratory system to external pressure oscillations. However, most current devices are large and high cost, hence, the test remains sparingly used. To address this problem, we verify the feasibility of a smart and portable forced oscillation device based on a small subwoofer and ultrasonic sensor that is targeted at point-of-care pulmonary function testing. In this thesis, we first develop and optimize the signal processing algorithm for robust impedance estimation under low SNR. Then we characterize the signal quality of programmable oscillatory waveforms with varying frequency, amplitude and duration, and determine the optimal signal type for the portable device. Next, we develop the algorithm for automatic waveform adaptation and real-time error elimination, and assess its robustness with manually created artifacts during the tests. Finally, we evaluate the accuracy and repeatability of the device against both mechanical models and a small group of healthy human subjects. The results show that the error detection algorithm could successfully eliminate various artifacts including swallowing, glottis closure and abnormal breathing. With the adaptive oscillatory waveforms, the coherence function is above the clinical acceptance threshold 0.9 for all frequencies between 5Hz to 30Hz, and the relative measurement error of respiratory resistance is less than 10%. The device yields good repeatability and satisfies the clinical diagnostic requirements for point-of-care tests.
Portable forced oscillation device; point-of-care; adaptive signal generation; real-time artifacts elimination