Abstract
This paper presents the design of a novel oscillometry device for the measurement of respiratory mechanics based on piezoelectric bimorph actuator technology. To predict performance for measurement of human respiratory mechanics, a dynamic model was developed based on a bimorph piezoelectric actuator driving a linear resistance mesh screen including subject’s respiratory impedance loads, and realistic breathing noise. Model performance was also validated in a prototype device. We found that while breathing noise substantially lowered SNR, the model could produce sufficient pressure and flow for acceptable SNRs exceeding 35 dB, and accuracies exceeding 99%. Satisfactory accuracy could be achieved with load impedance errors less than 3%. Maintaining the air-gap around the oscillating mesh with a resistance against the leak greater than 0.38 cmH2O/L/s maintained good performance, with an acceptable 4 dB decrease to SNR. Moreover, this work provides multiple solutions to host higher amounts of noise and nonlinearities. These results indicate that the development of an accurate lightweight portable single frequency FOT device is feasible.
Highlights
Oscillometry known as the Forced Oscillation Technique (FOT) superimposes fluctuations in airway pressure on normal breathing to measure the mechanical impedance to airflow of the respiratory system for diagnosing and monitoring lung diseases [1]
This paper presents the design of a novel oscillometry device for the measurement of respiratory mechanics based on piezoelectric bimorph actuator technology
Using FOT is possible in very young children to elderly patients as it is easy to perform unlike the current standard approach, which involves a learned maximal forced expiration that is difficult for many patients
Summary
Oscillometry known as the Forced Oscillation Technique (FOT) superimposes fluctuations in airway pressure on normal breathing to measure the mechanical impedance to airflow of the respiratory system for diagnosing and monitoring lung diseases [1]. Respiratory impedance is a complex quantity with a real part: respiratory resistance (Rrs) largely due to airflow resistance and an imaginary part: reactance (Xrs) arising from elastic properties of the lung and chest wall and the inertia of the air. FOT Devices must reliably produce oscillatory waveforms even when perturbed by breathing, and must accurately measure pressure and flow due to the oscillations, over a wide range of patient respiratory impedances, and compensate for any self-impedance of the device and disposable filter. Current FOT devices use either a loudspeaker or oscillating electromagnetic actuator which results in a device that is larger or heavier than typical spirometers
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