Case Study: How Precise Low-Flow Pumps Help Automate Diabetes Control Device

ByLance T. Lee

Apr 25, 2022


Profile Institut für Stoffwechselforschung GmbH [institute for metabolic research] used Watson-Marlow OEM pump technology in a medical device designed to automatically measure and control blood sugar in patients with diabetes.

Each of Profil’s ClampArt glucose clamps uses three Watson-Marlow 400ST/RX pumps. A total of 28 ClampArt devices have already been completed and have been in routine use in clinical practice for over eight years, resulting in several hundred thousand hours of operation without a single pump failure.

Profil is a Contract Research Institute (CRO) specializing in conducting clinical trials of new diabetes drugs. One of its main areas is the study of glucose clamps – complex procedures that determine the properties of newly developed insulin preparations.

After administering the blood sugar-lowering drug to a patient, a small amount of blood is drawn continuously over a period of up to 48 hours to analyze blood sugar minute by minute. Until recently, these tests had to be done manually, which made them laborious and prone to issues such as inaccuracies and human error.

ClampArt is Profil’s automated glucose clamp solution. After entering a target blood glucose level, known as a clamp level, ClampArt can monitor and maintain that level by automatically delivering glucose. Besides measuring glucose concentrations at the bedside, the method of pumping such small amounts of fluid, both accurately and at very low flow rates, was one of the major technical challenges to overcome.

Selection dilemma

“Selecting an appropriate pump was an important factor in the development of ClampArt,” says Dr. Tim Heise, Principal Scientist and Co-Founder of Profil. “Initially, we experimented with several different pumps which turned out to be unsuitable. The main problem was that the glucose clamps work with very low flow rates of only 7.5 ml/h and therefore with tube diameters of only 0.4 mm.

None of the pumps originally tested by Profil could provide the necessary precision at such low flow rates. In addition, the tubes could not withstand the constant and high contact pressure. That is, until the institute investigates Watson-Marlow.

Watson-Marlow recommended using their OEM 400 series pumps, which have been designed for flow rates from just 0.2 µl/min up to 2 l/min. When combined with a wide selection of pumpheads and drive units, pumping solutions can be configured to meet specific customer needs.

Trio of pumps

In ClampArt, a total of three Watson-Marlow 400ST/RX pumps are deployed. The first supplies the body with a mixture of sodium chloride and heparin to prevent the blood from clotting, while the second “sensor” pump continuously draws a small amount of blood from the patient. This is pumped into a mixing chamber, where it is mixed by the third pump with hemolysis buffer and transported to the measuring unit so that the glucose concentration can be measured.

The solution involved minor customization as the small tube diameter of 0.4mm meant that the gap between the pumphead rollers and the track was too large. As a result, Watson-Marlow increased the size of the rollers in the pumphead, making the space the ideal size for the tubing used. This solved the problem of high contact pressure and offered longer tube life.

Passed result

“Watson-Marlow gave us expert advice during the development process,” confirms Dr. Heise. “We are very pleased with our purpose-built pump model as it delivers the low flow rates we need with the highest degree of accuracy.”

Since glucose clamps can last up to 48 hours, the pumps must work reliably. Test patients usually stay at Profil overnight, so the pumps should run as quietly as possible. The pumps can also be programmed and individually controlled by means of a separate command line, while in terms of safety they operate at only 12-60 V and stop automatically each time the lid is lifted. This made it easier to obtain CE certification for ClampArt.

“After several years of research and development, we have created with ClampArt an analytical instrument that has been used successfully in our clinics since 2012. To our knowledge, there are no competing products with comparable performance in Europe or the USA. ,” concludes Dr. Heise.

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