Detection of micro bubbles in the extracorporeal circulation

The detection of the number and the size distribution of micro bubbles in blood is of high importance, particularly with the extracorporeal circulation. A system is presented which allows a continuous measuring of the micro bubble distribution of tube flows in a range between 5 and 120 μm in diameter. The measuring system is based on a 2 MHz ultrasound Doppler system with special ultrasound probes for the coupling to the 3/8" tube. The device avails of two measuring channels for measurements at filter systems. During the measuring a computer-controlled registration and evaluation of the bubbles as well as a self-calibration of the system is performed. The bubble size is evaluated due to the backscattered Doppler signal and is corrected by means of a reference signal according to the measuring conditions. During the clinical tests arterial filters of different manufacturers were evaluated