Hemodialysis is a complex process requiring the increased control of some parameters, such as dialysis dose, blood perfusion rate, ultrafiltration, blood volume, its composition and etc. To solve the problem of control the blood during dialysis was designed the monitoring system of air inclusions - air bubbles. A very important part of this system is the ultrasonic air detector. It is set to venous blood highway - at the exit of blood from the dialyzer, and determines the presence in the cleaned blood any air inclusions by measuring the velocity of ultrasound in the analyzed multiphase medium - the blood, thus informing the doctor about the quality and security of hemodialysis procedure.

Keywords: Air embolism, bubble trap, air detector, speed of ultrasonic vibrations, the pulse-frequency method of measurement the ultrasonic speed.