Ultrasonic gas monitor developer eyes medical applications

A sensor that measures the acoustic bulk properties of gases flowing through it looks set to lower the size and costs associated with such devices in medical equipment.

Developed at Cambridgeshire-based TTP, the ultrasonic device – dubbed SonicSense – measures the speed of sound in a gas to determine its composition.

Medical applications include respiratory monitoring, capnography, anaesthesia and COPD monitoring.

Andrew Baker-Campbell, part of the team that developed SonicSense, explained that the simplest application for a medical user would be for mixing different gasses, or monitoring of the mixture of different kinds of gas.

He told The Engineer: ‘In a ventilator, when you’re supporting a patient’s breathing, you might want to mix room air or dry compressed air…with oxygen to give the patient a richer breathing mixture. Controlling the degree of addition oxygen you put in is really important: you don’t want the person to either hyper-or-hypo-ventilate.

‘The measurement essentially says “the speed of sound in the room air is this, the speed of sound of the oxygen is this”, therefore you can plot the speed of sound of a mixture of those two gasses, and by measuring the speed of sound you can infer the composition.’

It is claimed that SonicSense devices would cost between £3 and £6 each in volume production compared to approximately £120 for paramagnetic systems for oxygen, and over £240 for infrared devices that measure carbon dioxide. Prototype devices developed for existing clients have a diameter of 24mm and a depth of 18mm, a dimension TTP believe can be reduced to less than 5mm. 

SonicSense gas sensors are set for manufacture in the next 12 months when they will be incorporated into a medical device being developed by a large multinational healthcare company that cannot be named for reasons of confidentiality.

Baker-Campbell added that SonicSense devices are not restricted the medical sector and that applications are envisaged in gas safety, plus industrial monitoring and control.