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Spring technology at the heart of new blood flow monitor

Spring technology at the heart of new blood flow monitor Innovative spring technology is proving to an impressive new medical device that NHS authorities and trusts can no longer afford to ignore.

Following a recent recommendation from NICE (the National Institute for Clinical Health and Excellence) and predicted savings of £1,100 for every hospital patient undergoing surgery, the CardioQ-ODM (oesophageal Doppler monitor) from Deltex Medical looks set to transform patient care. Deltex Medical originated in 1989 when Deltex Instruments merged with Doptek. While the former became the dominant partner, the Doppler technology of the latter is the driving force behind the company's success today.

The CardioQ-ODM measures blood flow velocity directly in the central circulation. The device is minimally invasive with a single-use probe being inserted into the oesophagus, hence averting the requirement for incision. The probe emits ultrasound waves that bounce off blood flowing in the aorta, measuring its velocity. This allows surgeons to see how much oxygen and nutrients are reaching vital organs and tissues, and subsequently deliver the right amount of blood or fluids.

It's an effect that cannot be achieved using conventional blood pressure readings, helping avoid complications, speed recovery and save time spent in hospital - around 3.5 days less on average. However, none of this would be possible without a vital product supplied by expert spring, bent wire form and assembly manufacturer, William Hughes.

Electrical signal wires connecting the probe tip to the CardioQ-ODM are housed inside the length of a silicon tube. However, because the disposable probe needs to be inserted down the oesophagus, flexibility and ease of manipulation are key functions, and these can only be delivered using fine wire spring technology lining the silicon tube. "Originally we were using a competitor of William Hughes," explains the company's operations manager, Dr Graham Lowe. "However, we started to see inconsistencies in stiffness along with increasing amounts of particulates. As a result, around six years ago we turned our attention to William Hughes and they helped us develop a better spring, introducing a heat treatment process which de-stresses the wire before use. A tension test was also devised to guarantee spring consistency, even if it has been in the packaging for an extended period."

Closed coil spring
The closed coil spring manufactured by William Hughes for the CardioQ-ODM is around 550mm in length with an outside diameter of 3.4mm. Pre-galvanised steel wire is the selected material (stress relieved) and each spring must be free of burrs and particulates. As a result, springs are cleaned rigorously using compressed air before intensive visual inspection is applied to ensure complete product cleanliness. Once the springs arrive at Deltex Medical's headquarters in Chichester, depth markers are fitted telling the surgeon how far to insert the probe. Subsequently, the springs are inserted into silicon tubes which are inflated slightly to ease the task.

At present, Deltex Medical, a £6.4 million turnover business, manufactures around 70,000 such devices every year. However, with around one million operations taking place annually in the UK, the potential market is vast. And this is without considering other applications such as intensive care or veterinary - or international markets: the USA, Canada, France and Spain are all in the process of completing national audits. Volumes could quite feasibly soar.

On top of the NICE recommendation for Deltex technology, a new Enhancement Recovery Partnership report from the NHS has re-stated that fluid management is an essential platform to enhanced recovery in post-surgery patients. Furthermore, if fluid management is performed in the way recommended by NICE, there are incentives on offer via CQUIN payments. As one of the eight high impact innovations listed in the recent NHS Innovation Health and Wealth document, the use of CardioQ-ODM could provide health authorities with up to 2.5% of annual budget, a not inconsiderable sum. What's more, if a health authority chooses to ignore the recommendation it will not be eligible for CQUIN payments in the subsequent financial year (2013-14). Budget managers are unlikely to let this happen. The impact on Deltex Medical could be extremely significant. In fact, the first ripples of the changing tide are already being felt, in the first quarter of 2012 demand has grown 40% in the UK alone. No other manufacturer is producing Doppler-based devices - alternatives deploy a reusable probe which requires cleaning. "The development of a low cost spring for our disposable probes has provided Deltex with genuine market differentiation," says Dr Lowe. "Many of our direct competitors have withdrawn from the market entirely in recent years."

The NHS Technology Adoption Centre has completed a national audit on CardioQ-ODM technology, stating that: "Optimal management of fluid balance during major surgery is considered a key factor in improving surgical outcomes. Innovative and minimally invasive monitoring of cardiac stroke volume using oesophageal Doppler technology now enables the anaesthetist to safely and accurately administer intravenous fluids during surgery."

Dr Lowe adds: "With a million operations a year each generating savings of £1,100, the NHS could save £1 billion annually. The typical return on investment for a single monitor is just 10 days."

And there's another potential revenue stream for Deltex that is gathering pace following the company's development (in partnership with William Hughes) of a version for patients who are awake. This features an open coil spring as opposed to a closed coil, providing a softer and more flexible action, and facilitating probe insertion via the nasal passage.

"Initially we looked at retaining the closed coil design but using a finer wire," says Dr Lowe. "However, although this makes it softer, it also increases the number of coils and so less energy is transferred along the spring, making it difficult to manipulate. With William Hughes we created an open coil, patent-pending alternative, which gives a softer spring laterally while actually reducing the number of coils from 750 to 440. It's always difficult to predict future demand, but conceivably this device could become the long-term standard for all applications - awake and in-surgery. Watch this space."
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