Uncrossing the lines

Brussels, 22 Sep 2003

The ISOLOK project is developing a novel system of components for delivery of drugs through spinal, naso-gastric or vascular tubes. They will remove the danger of air influx or giving drugs by the wrong route.

During clinical treatment, many different drugs are administered to patients through small-bore tubes connected into the bloodstream, the alimentary tract or into the epidural space of the spinal canal. Over the years it became clear to UK surgeon Dr Joe Peters that sporadic deaths had occurred because of accidental connection of the wrong input, or because of connectors coming apart and allowing a sudden influx of air.

One standard to fit all

Vascular, naso-gastric or spinal tubes all have the same connection, with a specified geometry and an ISO standard. While this is adequate for hypodermic injection, in the longer term they can pull apart. If air is taken into the blood system, which can happen very rapidly because of the negative pressure created by every breath, a fatal air embolism can occur. Patients can bleed through vascular tubes if they come apart – especially dangerous for renal dialysis patients.

The main danger with spinal injection components is that of misconnection and the wrong drugs being administered into the epidural space or spinal canal. For example, in treatment of leukaemia a spinal and an intravenous drug need to be given at the same time. Giving a spinal drug intravenously gives a massive shock to the heart, which can lead to death. Accidents of this sort have highlighted the need to discontinue using the same type of syringes, nozzles and connectors for drug administration by these different routes.

In 1995, Dr Peters produced basic designs for components that would readily distinguish between the different systems and prevent influx of air. "It's a historical paradox that we have continued using systems which allow these risks," he says. "When leaded petrol was introduced, changes were quickly made to petrol pump nozzles so users could not put the wrong fuel in their car."

Around Europe, other clinicians were noticing the problem, and a technical committee of CEN – the European standards organisation – has now recommended that there must be differentiation by design for the tubes of the various functions going into and coming out of the patient.

Differentiated systems essential

Dr Peters and his partner John Watkinson formed Clinipart to progress this and other design ideas. Clinipart is now the co-ordinator of the Commission-funded ISOLOK project.

ISOLOK is in its early stages, but the designs for the differentiated system components are already prepared. They will include novel female connectors with drug escape mechanisms to eliminate the possibility of accidental administration of the wrong drug to the patient. A new needle hub design will replace the standard Luer connector for lumbar applications, and developments using membrane valves will prevent air influx.

"More thorough testing is vital too," insists Dr Peters. "Currently systems only have to pass a pull test, a pressure test and an aspiration test. If components have to stay in place on the body for some time, they must be able to keep that connection intact (watertight and airtight) against movement or vibration."

The ISOLOK project and its participants hope to make an input into the work of the CEN committee towards possible new, tighter European standards. Patents have already been granted for the operation of the connectors, and the hope is that by the end of the two-year project, pre-production prototypes will be complete.

Medical device and engineering expertise

ISOLOK brings together a wide range of expertise in medical devices together with some new technologies from other sectors:

The Fraunhofer Technology Development Group (TEG) in Germany and the Product Engineering Research Association (PERA) in the UK are analysing and advising the project on the qualities and specifications of system components to meet the needs of medical professionals and patients;
Vistamed (IE) has expertise in fine-bore extrusion for injection moulding, and will contribute to manufacturing;
Melab (DE) is an international testing house for medical devices and will participate in the systems' development;
Raytech (BE) is expert in laser beam micro-engineering and will advise on the use of lasers to burn minute pores through silicone membranes, which may be applied to the development of new types of entry ports into the blood vascular system; and
Rocket Medical (UK) is an SME with expertise in neurological and vascular products.

All are keen to contribute to the ISOLOK project, as it has the potential to set new standards for this area of medical devices – both in general and quite literally in view of the work of the CEN committee. Dr Peters says that PERA was particularly helpful in helping to pull together the project consortium, through its wide knowledge of the medical device and engineering industries. The European Commission also helped the project co-ordinators in organising the programme of work.

DG Research
http://europa.eu.int/comm/dgs/research/i ndex_en.html
Item source: http://europa.eu.int/comm/research/indus trial_technologies/22-09-03_pro-isolok_e n.html