Design and Evaluation of an Ultrasonic Oxygen Sensor for Medical Ventilators

Abstract

Many people are affected by respiratory system diseases and need medical ventilators to help them breathe, often it is also necessary to be able to add extra oxygen to the breathable air meaning it must be possible to measure the oxygen concentration in the ventilator. Right now, the most commonly used sensors for this purpose are electrochemical sensors that are expensive, have slow response-times, not environment-friendly and cannot measure gas flow. As an alternative solution, this thesis proposes a design for an ultrasonic oxygen sensor that is capable of measuring both oxygen concentration and air flow speed, the disadvantage however is that the ultrasonic sensor is non-selective. The design includes a hardware, software and mechanical solution and the tests carried out on the developed system showed that the sensor was multiple times quicker than the reference (electrochemical) sensors. Furthermore, the accuracy of both concentration and flow measurements were within 2.5% of the reference sensor and within the design goals.