In adults who need a nasogastric tube for a short time, pH testing was the best initial approach followed by X-ray confirmation if pH testing wasn’t successful. pH testing was four times less expensive than X-ray confirmation and when used in sequence both were cost effective uses of NHS resources.
Nasogastric tubes are used to deliver liquids directly to the stomach. Tubes can be misplaced, often into the lungs, with serious consequences, so their final position needs to be checked. This can be done in two ways. pH testing which detects whether the expected level of acidity is present, and X-rays. Death or lung damage that arises from misplaced nasogastric tube is avoidable and should never happen, something the NHS calls a “never event”.
Updated advice from the NHS in England restates the position that pH testing should remain the first choice to detect correct placement. This cost analysis supports the current approach of pH testing followed by X-ray if necessary.
It is important to consider the training of staff who carry out the test or read X-rays. A resource set to support providers is available from NHS improvement. Especially important if the harm from these events is to be reduced to zero.
Why was this study needed?
Over 790,000 nasogastric tubes are used in the NHS each year. They are inserted through the nose and passed down to the stomach.
Healthcare professionals carrying out the procedure are unable to see exactly where the tube is going. The end of the tube may pass into the lungs which can cause serious harm, or even death, if liquids are then administered. Because of this, checks are recommended after the initial placement before the tube is used for any liquid.
During 2009/10, there were 41 never events reported in the NHS where a misplaced nasogastric or orogastric tube was not detected prior to use. As these should never happen, they are called “never events” and are monitored closely in the NHS. Detail in these monitoring reports suggest there are issues with x-ray interpretation at all times, and there may be increased risks from nasogastric placement or x-ray checking at night.
Because the procedure is still recognized as a cause of avoidable mortality and morbidity this author sought to study the cost and effectiveness trade-off between the two most commonly used methods as this has not been done previously.
What did this study do?
This cost utility analysis utilised three sources of evidence to populate a decision tree model. Effectiveness data was gathered from a systematic review and meta-analysis. Three studies were included on chest X-rays, three on pH testing and three on the probability of obtaining a sample for the pH test.
Quality of life patient outcomes were not covered in the literature, so were calculated by asking 23 adult surgical patients to rate the imagined impact of different nasogastric tube scenarios. These ranged from no complications to serious complications. Cost information was obtained from current NHS prices and staff costs.
The study was conducted with reference to healthcare in Scotland, but should be applicable to the rest of the UK.
What did it find?
- If X-rays replaced pH testing completely as the first line test, this would cost £11,544 per quality adjusted life year (QALY).
- The cost of all testing and staff costs associated with pH testing was £43.20 and for X-rays the equivalent was £158.64.
- Compared with no checking, X-ray delivers a slightly higher QALY gain at 0.12 then pH testing at 0.11.
- When the two scenarios were modelled the added value, or incremental cost effectiveness ratio, for pH testing was £392.73 per QALY, over a third lower than X-ray at £1,322. Both these ratios signify good value for the NHS.
- The 23 people assessing the impact of nasogastric tube placement recorded a slight negative effect on health even for scenarios without complications. This rose in line with the severity of complications.
Sensitivity analyses indicate findings may be altered by tube aspiration success rates and X-ray interpretation errors.
What does current guidance say on this issue?
The National Patient Safety Agency reviewed incidents of misplaced nasogastric tubes in 2011 and reiterated the NICE 2006 guidance that nasogastric tubes should only be inserted if sufficiently experienced staff are available to check the position. Many cases of misplacement occur out of hours.
NICE recommends that correct placement be confirmed by aspiration and pH testing. If aspiration is not possible or the result is unclear, then X-ray is recommended. These steps should be repeated after any vomiting, retching, coughing or if the tube appears to have come out or there are new breathing problems. US, Canadian and European guidance suggests all patients should undergo x-ray confirmation.
Further detailed NHS guidance reiterating the initial nasogastric tube placement check was published in July 2016 and includes practical examples of how providers can implement and embed guidance in their organisations.
What are the implications?
The serious harms that can be caused by nasogastric tube misplacement are often avoidable and the cost of treating complications may be substantial. The findings from this study go some way to alleviating safety concerns by supporting existing NICE, NPSA and NHS recommendations.
If one of the 25 preventable events called “never events” in the NHS occur there is a financial penalty for the provider of £10,000 levied on top of the recovery of costs of care and procedures should a death occur.
Whilst pH testing may be the most cost effective and comparable to chest X-ray in terms of patient outcome, there remain some questions surrounding the correct interpretation of test results. Ensuring healthcare professionals have adequate support and training should help minimise the risk of error regardless of the method of checking employed and might eventually reduce these “never events” to zero.
Citation and Funding
McFarland A. A cost utility analysis of the clinical algorithm for nasogastric tube placement confirmation in adult hospital patients. J Adv Nurs. 2016. [Epub ahead of print].
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
NHS Improvement. Patient safety alert: Nasogastric tube misplacement: risk of death and severe harm through failure to implement previous guidance. London: NHS Improvement; 2016.
NHS Improvement. Resource set. Initial placement checks for nasogastric and orogastric tubes. London: NHS Improvement; 2016.
NICE. Nutrition support for adults: oral nutrition support, enteral tube feeding and parenteral nutrition. CG32. London: National Institute for Health and Care Excellence; 2006.
NPSA. Patient Safety Alert NPSA/2011/PSA002: Reducing the harm caused by misplaced nasogastric feeding tubes in adults, children and infants. London: National Patient Safety Agency; 2011.
Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre