Development and performance testing of an ECMO ultrasonic blood flow sensor

Extracorporeal Membrane Oxygenation (ECMO) is a technique used for extracorporeal circulation and respiratory support, primarily for life-saving treatment in patients with respiratory failure unresponsive to conventional therapy. Ultrasonic blood flow sensors represent a critical component of ECMO systems, facilitating precise real-time blood flow measurements. The present study details the design and development of a novel clamp-on small-caliber ECMO ultrasonic blood flow sensor prototype (UBFS). Flow tests were conducted to analyse the sensor's response characteristics in 23 °C water and 37 °C imitation blood medium. A water-imitation blood calibration model (M_Water-iBlood) was proposed to replace blood with water for calibration, thereby reducing the cost of sensor testing. The incorporation of a Kalman filter algorithm into the sensor was undertaken to enhance measurement stability and accuracy. The experimental setup utilized a standard fluid flow calibration device, with an uncertainty of 0.2 %, a testing range of 0–10 L/min, and temperatures maintained at 23 °C and 37 °C, using water and imitation blood solutions as the test media. The results demonstrated that for flow rates up to 1 L/min, the sensor's measurement accuracy was within ±3.7 %, and for the flow rates of 1–10 L/min, the accuracy improved to within ±0.93 %, with repeatability within ±0.7 %. Finally, the UBFS was compared and evaluated through serial testing with commonly used small-diameter clamp-on industrial ultrasonic flow meters and medical ultrasonic flow meters.