From bench to bedside : the development of a location indicating nasogastric tube

BackgroundNasogastric tubes are frequently used in clinical practice. Correct placement in the stomach must be verified on passing the tube and before every feed or administration of medicine. Current methods of confirming placement are limited and complications related to incorrect placement are well documented. The need for an easy, safe, reliable bedside method for verifying nasogastric tube placement has been identified.AimTo develop a manufactured prototype of an effective, sensitive and reliable nasogastric tube which self-indicates its position and is ready for clinical investigation in patients.MethodsA pH sensitive redox polymer, vitamin K1, was applied to the tip of 40 hand adapted nasogastric tubes (iteration 1) that were then assessed in pH solutions and clinical samples. Results were used to inform the design of manufactured prototype tubes (iteration 2). A total of 60 iteration 2 tubes were prepared and evaluated in a range of fluids, resected stomach tissue, gastric fluid and sputum. Documentation for regulatory approval of the new device was prepared and the intellectual property protected in preparation for licensing with a commercial partner. A User Network was established to inform the design and development of the device.ResultsA total of 100 prototype tubes were evaluated. One third of iteration 1 prototypes and all of iteration 2 manufactured prototypes, generated a measurable current. Variation in the size and nature of the gastric tissue samples limited definitive conclusions that could be drawn from these experiments, but guided design choices in an iterative manner. However experiments with human gastric fluid demonstrated that, using linear sweep voltammetry, zero current potential gave clearer distinction of pH than amperometry in the desired pH range. Patent protection (granted in Australia, USA and Canada and pending in Europe) of the associated intellectual property and completion of the regulatory approvals process enabled negotiations with a number of companies interested in manufacturing the novel medical device for clinical trials. A User Network was established and a range of communication strategies developed to ensure that the development of the device was informed by current experience of lay and professional users.ConclusionThis thesis documents a translational research study in which understanding of electrochemistry was applied to a current clinical problem generating new knowledge. It was demonstrated that, when a redox polymer is applied to the distal tip of a nasogastric tube, the electrochemical reaction can be measured at the proximal end and assessment of the zero current potential distinguishes fluids of different pH values. New understanding of the reality of user involvement in the development of medical devices was generated and a flexible approach of a User Network is advocated. A commercially manufactured device, with appropriate regulatory approvals was produced ready for clinical trials and patents granted or pending across the globe.

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