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

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.

Naso-gastric tubes (NG-tubes) are used worldwide each year in hospital and community settings (UK-1million; US-1.2 million; EU-10million) to give enteral feeds and medicines to patients unable to swallow/tolerate oral feeds (e.g. from critical illness, deteriorating consciousness level, neurological condition (stroke) or post gastro-intestinal surgery). Accidental misplacement during blind insertion into the respiratory tract or pleura occurs in 1-3% cases, and into the oesophagus in 19%, with later tube migration in up to 50%. If fluids are given down a misplaced tube, serious patient harm or death can result, an NHS Never Event.

The recommended first-line NG-tube placement test is to obtain aspirate up the tube and check its acidity with pH paper. A pH of 1 to 5.5 is a 'safe range' to exclude respiratory tract misplacement and to use the tube. Obtaining aspirate is difficult (50-85% chance of success), and pH readings may be unclear. The second-line test is then an X-ray which can be misinterpreted (seen in 57% of never events), is costly, exposes patients to radiation, causes delays in feeding and increases movement/travel of seriously ill hospitalised patients or community patients needing longer-term feeding. A different approach is needed.

Our 3-year project aims to produce and test a new portable, sensor-based, NG-tube placement device (NG-Sure). It will measure gases and volatile chemicals at the NG-tube tip, to create 'VOC (volatile organic compound) fingerprints' and a pH reading (without needing aspirate). Fingerpints will differ according to tube location (stomach, lungs or oesophagus). We have proved clinical feasibility of our idea on 33 paired gastric and breath samples, and aim to develop, produce and test a prototype device in patients with a chosen set of sensors. Our experienced team will involve patients, carers, and NHS staff throughout, and examine financial benefits and potential markets.

This applied, translational research project has a number of potential benefits to patients in hospital and community (home and residential care) settings, the NHS, to other healthcare providers (care homes, private healthcare providers), medical, nursing, dietetic and scientific communities, the UK and EU economy and wider society.

The device, NG-Sure, has the potential to produce outcomes with the following benefits:

Patients (within three years):
- NG-Sure will help reduce the risk of misplaced NG-tubes into a patent's lung or oesophagus and the associated patient harm, as a consequence of misplaced NG-tubes (e.g. aspiration pneumonia, malnutrition), and deaths.
- Reduced delay to the onset of feeding or medicines administration owing to waiting for X-ray verification (reported waits on average of four hours for these check X-rays), and interpretation of NG-tube position
- Less patient exposure to radiation from X-rays
- Improved patient and carer experience of NG-tube care using a new non-invasive device.
Inserting an NG-tube is necessary as part of the treatment for these patients, our sampling procedures will not be more invasive than this, and should not increase the discomfort for patients. In our earlier research there was no evidence of greater discomfort for patients during sampling processes. Use of the device may avoid the need for a patient to have an X-ray for NG-tube verification in the absence of aspirate or borderline/high pH.
- Increased confidence for patients, carers and clinicians (NG-tube users) as two measurements for NG-tube position will be provided to identify NG-tube location.

NHS (within three years):
- A safe, simple, convenient, and timely method of verifying NG-tube position in adults at the point of care in a cost-effective manner that could reduce the number of never events and serious incidents.
- Preliminary evidence on the safety (accuracy) and clinical utility (functionality) of NG-Sure, as well as an estimate of the reimbursement potential of NG-Sure to allow the NHS to make an informed decision regarding procurement
- Income generation for the NHS through a robust commercialisation plan and exploitation of arising IP
- Publication outputs in International peer-reviewed, professional and academic journals, with potential data sharing, as described and agreed in the project's Data Management Plan. Thus, raising the global profile of the host institution (Bradford Teaching Hospitals NHS Foundation Trust), its affiliated academic institution (Bradford Institute for Health Research), host Patient Safety Translational Research Centre, and NHS research.

NHS (within five to eight years):
- Potential savings to EU health providers of more than £400 million, assuming 10 million NG-tubes are used, and a 25% reduction in X-rays.
- Functionality to wirelessly upload data to hospital or primary care Electronic Patient Record (EPR) systems, or centralised reporting systems, to act as an alert for relevant staff
- Potential to translate VOC technology into other healthcare contexts, e.g. field of diagnostics - cancer diagnosis, detection of infections, screening for medication adherence, and positional checks for other invasive catheters/tubes.

The anticipated outputs of the research project include:
- Peer-reviewed evidence on the accuracy of VOC fingerprints coupled with pH detection as a position indicator for safe placement of NG-tubes in the stomach
- Evidence of safety testing for the NG-Sure device
- An effective method of sample collection and production of micro-sensors
- A prototype device for confirming NG-tube position.