Breath of fresh air

3 min read

Three neighbours have developed a device that could potentially improve, and in some cases save, the lives of people who suffer from breathing disorders and rely on bottled oxygen.

The fluid flow sensor device, Oxymon, monitors the supply of bottled oxygen to a patient, plus their respiratory rate. It fits to a standard cannula-type mask and uses sensitive monitors to measure, display and record pressure entering and leaving it.

Cannula-type masks fit over the ears, and have two tubes that feed oxygen into the nose.

Retired engineer David Jones from Hassocks, East Sussex, was inspired to produce Oxymon after his wife Heather died in 2006 after suffering from complications brought on by her treatment for Chronic Obstructive Pulmonary Disease (COPD).

Jones approached his neighbour, Noel Poncelet, an electronics engineer, to bring his idea to fruition. A third neighbour, Dr James Graham, helped arrange a clinical trial. The three have formed Oxymon to bring the device to market.

'When people are breathing oxygen, there is a little backpressure,' said Poncelet. 'Oxymon takes a reading from one pipe from the bottle to the cannula mask and it monitors this backpressure. This detects when the bottle is turned on and off, and the rate at which the pressure goes up or down.'

Pressure detection in Oxymon is achieved using a piezoelectric pressure-sensing device. The rate of change indicates whether the bottle is running low as opposed to simply being turned off, and a sudden high backpressure could indicate a blockage, such as if the pipe developed a kink or became squashed.

An indicator in the other pipe monitors the small changes in pressure in the patient's nose during breathing.

'Between the two measurements, you can detect whether the bottle is on and whether the patient is breathing from it, the rate they're breathing at, and a number of other measurements,' said Poncelet. 'Potentially you can detect risks such as the mask becoming dislodged, or if the oxygen isn't being taken in.'

Oxymon is attached to the head of an oxygen bottle, and a T-piece connects the pipes before running off into the mask, so it takes readings without interrupting the flow. It does not have a conventional on/off switch, but wakes up every few seconds to see if there is pressure to monitor. It then goes into sleep mode to save battery life.

It has an audible buzzer if a dangerous situation is detected, plus a number of coloured LEDs for feedback on factors such as oxygen supply and breathing rate. There is also an LCD which shows a bar that pulses up and down in synchronisation with breathing, an indication of low oxygen supply and whether breathing rate is normal or fast. Display options can be controlled through Oxymon's software.

The prototype is about 10cm on each side and 4cm deep, but at the next phase the developers hope to bring it down to the size of a mobile phone. The team made it using specialist sensors which are sensitive enough to measure small changes, but will not be damaged by excessive backpressure if a pipe is obstructed.

'After the breadboard version, we did a search on the web for local industries that would do the production of it, and we found Optisense in Horsham, which produces small production quantities of instrumentation equipment,' said Poncelet. 'The company produced the prototype we have now, sourced the components and revamped the design using the best available components. It also wrote the software and to date has built 40 prototypes.'

As a GP, Graham pointed out to the team that he had difficulty telling whether patients who were prescribed oxygen were following his advice when using it at home, so on his suggestion, the device includes a recording facility.

'It logs the time and date of when the oxygen bottle was switched on, when breathing was detected, when it was turned off and any alarm situations,' said Poncelet. 'This can then be downloaded to a laptop or PC and analysed so the doctor can see whether the patient achieved the recommended usage — something that has never been obtained before.'

An initial clinical trial is underway at a Brighton hospital under the supervision of Prof Mark Jackson, a consultant in respiratory medicine. The Oxymon partners have applied for European and US patents, and have received attention from a variety of manufacturers interested in licensing the product.

Berenice Baker