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HYDRAULICS & PNEUMATICS
low flow pumpS help automate diabetes
control devices
Needing high reliability pumps for its glucose clamp devices, the Profil Institut für Stoffwechselforschung (Institute for Metabolic Research) turned to
Watson-Marlow OEM pump technology T
he Profil Institut für Stoffwechselforschung (Institute for Metabolic Research) is a world-leading contract research institute
(CRO) that specialises in performing clinical trials on new diabetes medication. One of its core areas is the study of glucose clamps – complex procedures that determine the properties of newly developed insulin preparations. The Institute ClampArt glucose clamp devices
are designed to automatically measure and control blood sugar levels in patients suffering from diabetes. After administering the blood sugar-lowering medication to a patient, a small amount of blood is continually taken over a period of up to 48 hours in order to analyse the blood sugar level minute-by- minute. Until recently, such tests had to be conducted manually, making them labour intensive and subject to problems such as inaccuracies and human error. But, after entering a target
blood sugar level, known as the clamp level, ClampArt can control and maintain this level by administering glucose automatically. Bedsides measuring glucose concentrations, the method of pumping such small amounts of fluid, both precisely and at very low flow rates, was one of the main engineering challenges to overcome. “The selection of a suitable
pump was a big factor in the development of ClampArt,” explained Dr Tim Heise, lead scientist and co-founder of Profil. “Initially we
experimented with several different pumps that proved unsuitable. The main problem was that glucose clamps operate with very low flow rates of only 7.5ml/h and consequently with tube diameters of only 0.4mm.” None of the pumps tested originally by
Profil could provide the precision needed at such low flow rates. Furthermore, the tubes could not withstand the constant, high
FEATURE
contact pressure. The Institute therefore turned to Watson-Marlow for the solution.
Specifying the right pump
Watson-Marlow recommended its 400 series OEM pumps, which have been designed for flow rates of just 0.2µl/min up to 2l/min. When combined with a wide selection of pumpheads and control units, pump solutions can be configured to suit specific customer requirements. A total of three Watson-Marlow 400ST/RX
pumps are deployed in ClampArt. The first supplies the body with a sodium chloride and heparin mixture to prevent the blood from clotting, while the second ‘sensor’ pump continually takes a small amount of blood from the patient. This is pumped into a mixing chamber, where it is mixed by the third pump with a hemolysis buffer and transported to the measuring unit so that glucose concentration can be measured. The solution involved minor customisation as
the small tube diameter of 0.4mm meant the gap between the pumphead rollers and the track was too big. As a result, Watson-Marlow increased the roller sizes in the pumphead, making the gap the ideal size for the tubes used. This solved the problem of high contact pressure and offered the
additional benefit of longer tube life. Reliability was essential as the glucose
clamps can last up to 48 hours. Furthermore, test patients usually remain at Profil overnight, so the pumps need to operate as quietly as possible. The pumps can also be programmed and controlled individually by means of a separate control line, while in terms of safety they operate at only 12-60V and stop automatically whenever the cover is lifted. This made it easier to obtain CE certification for ClampArt.
A SucceSSful project
A total of 28 ClampArt devices have already been completed and have been used routinely in clinical practice for more than eight years, resulting in several hundred thousand operating hours without a single pump failure. Dr Heise said: “After several years of
research and development we have created, with ClampArt, an analysis instrument that has been used successfully in our clinics since 2012. As far as we know, there are no rival products with comparable performance in either Europe or the USA.”
Watson-Marlow
www.wmfts.com/en
NOVEMBER 2022 DESIGN SOLUTIONS 21
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