A High-Sensitivity Calorimetric Digital Flow Meter for Respiratory Monitoring and Proximal Flow Measurement in Neonatal Ventilation

In this paper, a high-sensitivity digital flow meter, featuring a low-power Thermo-resistive Micro Calorimetric Flow (TMCF) sensor fabricated by CMOS-MEMS technology, is presented for respiratory monitoring and neonatal ventilator-assisted ventilation. The packaging of the TMCF sensor has been meticulously optimized to achieve a 1.5-fold increase in sensitivity, resulting in a high sensitivity of 76.5mV/SLM in the linear range of -7.5SLM to 7.5SLM, and its heating power is only 2.23mW. The developed digital flow meter is quantized into a 14bit output within the flow measurement range of -40SLM to 40SLM, providing a high resolution down to 0.005SLM. With a remarkable response time of less than 11.5ms, corresponding to a bandwidth of 13.8Hz, and equipped with a 2kHz data update rate, our proposed digital flow meter excels in capturing abrupt changes in breathing and high-frequency respiratory signals. Furthermore, boasting a noise level below 0.0025SLM, the sensor system demonstrates the capability to identify subtle variations in respiratory flow. Based on its outstanding performance, the high-sensitivity digital flow meter effectively identifies simulated abnormal respiratory patterns, including apnea, polypnea, and hypopnea, and successfully performs closed-loop ventilation measurements for neonates on a ventilator. Therefore, it holds promising potential as a crucial sensing component with high precision, high sensitivity, and low power consumption in respiratory monitoring and neonatal ventilation therapy.