Volatile Biomarker Positioning of Naso-gastric Tubes to Enhance Patient Safety (Acronym: NG-Sure)

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Naso-gastric tubes (called NG-tubes) are passed through the nasal cavity down the back of the throat and through the oesophagus (food pipe) to the stomach and are used to give medication, fluids or liquid feeds to patients. Each year one million NG-tubes are used in the NHS in hospital, community (care home and home settings), to give fluids, feeds and medicines into a patient's stomach, if they cannot swallow or drink, or need surgery or intensive care. There is a small chance that NG-tubes can accidentally be put into the lungs (1 to 3 times out of 100) or move from the stomach into the food pipe (19 times out of 100). If liquid is then given down the misplaced tube, serious harm or death can result, this is known in the NHS as a Never Event. Since 2011 there have been 132 such 'never events' reported and, despite the publication of national patient safety alerts in 2011, 2012 and 2016 warning of the dangers of misplaced NG-tubes, the number of reported events has not decreased, with 26 cases of serious harm and death occurring in 2016/17 alone. Until now, the recommended way to check that an NG-tube is placed in the stomach is to get some fluid up the tube known as aspirate, and test how acidic it is using pH paper. A reading below 5.5 indicates the aspirate is acidic and that the tube is in the stomach. However, getting stomach fluid is difficult with a 50-85% chance of success of getting some, so X-rays are often used instead. X-rays can be interpreted incorrectly (as seen in 57% of never events). Moreover, X-rays cost more, cause delays and inconvenience for patients and staff, as well as exposure of radiation to patients. A different approach is needed. Our project aims to develop and test a new portable, sensor-based device (called NG-Sure) to give an accurate check of NG-tube position. NG-Sure works using sensor technology, measuring gases or chemicals, known as volatile organic compounds or VOCs, at the end of the NG-tube to create 'smell fingerprints' in addition to a pH reading. These fingerprints are different depending upon where the tube is situated (stomach, food pipe or lungs). We have carried out a study to test whether it is possible to accurately distinguish smell fingerpints for stomach aspirate and breath from a patient's lungs. Our results were 100% accurate, all breath samples were correctly identified as breath and all gastric samples were identified as stomach aspirate. We have discussed our idea with different clinical groups, in hospital and community settings, and they have told us that a solution to the problem of NG-tube placement is required. In the work proposed here we now want to develop, produce and test a prototype NG-Sure model. To do this we will:- Generate additional smell fingerprints and pH readings for breath, food pipe and stomach samples from patients to add to our existing database of smell fingerprints- Work out a way of getting the gas and chemical samples needed to measure the smell fingerprints and pH readings up the patient's NG-tube when it is in place- Work closely with healthcare staff and patients and their carers throughout the project to understand their needs and requirements as we design and build our prototype device- Test the safety and function of our prototype device once built in a clinical study with 200 patients by comparing our device against X-rays taken in patients who need the position of their NG-tube confirming before it is used- Study the financial benefits of our new device compared to current practice and identify ways to manufacture our device on a large scale.