Checking placement of nasogastric feeding tubes in adults (interpretation of x ray images): summary of a safety report from the National Patient Safety AgencyBMJ 2011; 342 doi: https://doi.org/10.1136/bmj.d2586 (Published 05 May 2011) Cite this as: BMJ 2011;342:d2586
- Tara Lamont, special adviser1,
- Catherine Beaumont, head of patient safety1,
- Alan Fayaz, specialist trainee in anaesthesia and intensive care2,
- Frances Healey, joint head of patient safety (response)1,
- Tanya Huehns, head of patient safety (strategy)1,
- Robert Law, consultant gastrointestinal radiographer3,
- Caroline Lecko, clinical lead (nutrition)1,
- Sukhmeet Panesar, clinical adviser (surgery)1,
- Michael Surkitt-Parr, joint head of patient safety (response)1,
- Mike Stroud, consultant gastroenterologist4,
- Bruce Warner, associate director of patient safety1
- 1National Patient Safety Agency, London W1T 5HD, UK
- 2London Deanery, London WC1B 5DN
- 3North Bristol NHS Trust, Bristol BS16 1LE, UK
- 4Southampton General Hospital, Southampton SO16 6YD, UK
- Correspondence to: T Lamont
Nasogastric feeding tubes are commonly used for people such as stroke patients with dysphagia or those on ventilators. They are generally used in the short to medium term (up to six weeks),1 rather than for longer term feeding, which occurs via gastrostomy tubes, jejunostomies, or gastrostomy buttons.2 Although feeding by nasogastric tubes is not routinely captured in activity data, about 170 000 tubes are supplied to the NHS each year.3 Most are inserted safely, but patients can be harmed if the tube is mistakenly inserted into the lungs or later becomes displaced from the stomach. If such errors are not detected before feeding, patients can develop serious complications, such as intrapulmonary feeding and aspiration pneumonia, which can be fatal. The position of tubes should therefore always be checked before feeding is started.
The National Patient Safety Agency (NPSA) issued guidance in 2005 for safe placement and position checking of nasogastric tubes.3 The guidance highlighted the unreliability of certain tests—such as the “whoosh” test (listening for bubbling sounds after air entry) and testing for acidity with litmus paper—and instead recommended testing with pH indicator paper as the first line check. It recommended checking x ray images as the second line test, although not for routine use. Since 2005, staff in England and Wales have reported 21 deaths and 79 cases of harm resulting from feeding into the lungs through misplaced nasogastric tubes. The single greatest cause of harm resulted from misinterpretation of x ray images, which accounted for 45 serious incidents, including 12 deaths. The NPSA therefore issued a further safety alert in March 2011 focusing on safe interpretation of x ray images.4 The guidance covers adults and children (not neonates), but this short article, based on the March safety alert, summarises advice for adults only.
A typical incident report reads: “Patient requiring NG [nasogastric] feeding. NG feeding tube resited through night. Portable chest x ray to confirm position of tube was viewed by nightshift ITU CT2 [intensive care staff] who then advised the nurses to commence feeding with NG feed. Patient was fed for approximately 1 and 1/2 hours giving 200 ml of feed. At around 0850 patient became very distressed, hypertensive, desaturating and coughed up NG feed into ventilator tubing. The NG feed was stopped. Duty ITU doctors were alerted to the problem and patient was reviewed. The CXR [chest x ray image] was reviewed and the NG tube was found to be positioned in the left lung.”
Problems identified by the National Patient Safety Agency
Analysis of incidents involving placement of nasogastric feeding tubes since 2005 suggested that misinterpretation of x ray images was the largest single contributory factor, accounting for about half of all serious incidents and deaths. Other findings indicated that healthcare professionals were not following the original NPSA guidance. Healthcare staff were:
Feeding patients despite obtaining nasogastric aspirates with a pH of between 6 and 8
Instilling water down the tube before obtaining an aspirate
Not checking tube placement by any method
Not documenting any confirmation of such checks.
Because of the preventable nature of this harm, the misplacement of nasogastric tubes was confirmed by the Department of Health in March 2011 as being a “never” event—that is, one of a restricted list of serious avoidable events that could incur financial penalties for providers.5 Forty one never events relating to misplaced nasogastric tubes were reported between 2009 and 2010, thus confirming problems with interpretation of x ray images and risks in procedures done outside usual working hours.6
Early results from an NPSA audit in 2010 suggested great variation among 166 junior doctors at five pilot hospital sites in England and Wales, with low awareness of harm and continued use of unreliable checks such as the whoosh test and testing for acidity with litmus paper. Less than a quarter of the junior doctors were aware of the existing guidance, and less than a third of junior staff surveyed had received formal training on interpretation of x ray images for misplaced tubes.7
What can we do?
The NPSA safety alert asked organisations to make systems safer by:
Identifying a clinical lead to implement actions
Reviewing policies, training, and competency frameworks
Ensuring stock of correct equipment (approved pH indicator paper and radio-opaque tubes with clear length markings), and
Avoiding placing nasogastric tubes outside usual working hours whenever possible.
Resources included decision algorithms, placement checklists, and links to an e-learning module for junior staff (www.trainingngt.co.uk).
Individual clinicians should ask themselves:
Is nasogastric feeding appropriate for this patient? Do not use this method of feeding if the patient has a high risk of aspiration or any deviation in normal anatomy, such as pharyngeal pouch, strictures, or facial trauma. In these cases, seek advice as fluoroscopic guidance can often be used. Because of the risks of intubation, the decision to feed after assessment of the patient must be agreed by two competent professionals and recorded.
Does this need to be done now? Risks are greater at night time, when there is reduced access to a full range of staff and equipment.
Am I competent to do this? Ensure you have had training in safe insertion and checking, including interpretation of x ray images, and that you are supervised until competent. You can also use e-learning resources such as www.trainingngt.co.uk. If you do not feel confident to do this procedure, ask for help.
How can I check that the correct amount of tube has been inserted? Use NEX measurement (place exit port of the tube at the tip of the nose (N), stretching it to the earlobe (E) and then down to xiphisternum (X)) and confirm and record the external tube length before each feed to check that it has not moved.
Do I know how to test for correct placement (figure⇓)? Do not flush tubes or insert any liquid until you can confirm by testing with pH indicator paper (first line) or correct placement by radiography (second line).
What is a safe pH level? Obtain a nasogastric aspirate: if the pH level is between 1 and 5.5, it is safe to start feeding. To be sure, check with a competent colleague if the reading falls between 5 and 6, because of possible misinterpretations at this level. Always record the result and the decision to start feeding.
When should I arrange radiography? If no aspirate can be obtained or the pH level is higher than 5.5, request radiography and specify the purpose on the request form so that the radiographer knows that the tip of the nasogastric tube should be visible (that is, the film will be centred lower than for normal chest radiography).
What should I look for in the x ray image? You need to check that the tube is in the stomach (see box 1 and guidance from the NPSA4). Ask a radiologist if you are unsure about this.
After radiography, have I clearly recorded my decisions and next steps for the patient (box 2)? If the tip of the tube is well into the stomach (see NPSA guidance4), it is safe to feed. If the tube looks misplaced or the position is not clear, it is not safe to feed. If there is any chance that the tube is in the respiratory tract, take it out. You cannot rely on absence of respiratory distress as a sign of correct tube placement.
What about repeat checks? As tubes can be dislodged, tube placements should be checked at least once daily and before administering each feed or medication. Note that some patients, such as those taking proton pump inhibitors, will have persistently high gastric pH and so daily radiography would be impractical. Provided that the initial placement was appropriately confirmed and no other signs of dislodgement (such as retching or coughing) are present, repeat radiography would not usually be needed as long as the external length of tube remains unchanged. For further details see the NPSA’s supporting information4 and the 2003 guidelines commissioned by the British Society of Gastroenterology.1
Box 1 Ten pointers for interpreting an x ray image to check for correct placement of nasogastric tube
Can you see the tube?
Does the tube path follow the oesophagus?
Can you see the tube bisect the carina?
Can you see the tube cross the diaphragm in the midline?
Does the tube then deviate immediately to the left?
Can you see the tip of the tube clearly below the left hemidiaphragm?
If you think the tube is in the oesophagus, can you advance it?
Has the tube coiled higher up in the pharynx or oesophagus?
Does the length of tube inserted suggest it should be in the stomach?
Does the x ray image cover enough of the area below the diaphragm to enable you to see the tube clearly, or does it need to be repeated? To improve contrast and visualisation, you can manipulate the PACS (picture archiving and communication systems) windows
Box 2 Example confirmation of radiography results
19 January 2011, 10.30 A Smith—core surgical trainee
Radiography done at 10.15 today
Nasogastric tube passed down midline, past level of diaphragm and deviates to left
Tip is seen in stomach
Plan: Nasogastric tube is safe to use for feeding
A Smith [signature]
What else do we need to know?
No existing bedside method for testing the position of nasogastric feeding tubes is completely reliable, and little high quality research has been conducted in this area.8 A recent systematic review concluded that a pH level between 1 and 5.5 can exclude the possibility that the tube has been inserted into the lung but not the small possibility that the tube is in the oesophagus, carrying a risk of aspiration.9 Thus the review recommended lowering the threshold for pH testing from 5.5 (as in the NPSA 2005 guidance) to 4. However, when the NPSA consulted widely on this proposed change with stakeholders in 2010, they found that the disadvantages of lowering pH threshold seemed to outweigh the benefits. NHS staff expressed concerns about (a) the resulting increase in radiography procedures (leading to greater costs and more patients exposed to both radiation and the associated risk of misinterpretation of the x ray image), as well as access problems for patients in the community; (b) likely delays for patients needing urgent feeding; and (c) the difficulties of obtaining lower pH levels for certain patients, such as those taking prophylaxis for stress ulcers or those needing continuous feeds.10 The NPSA’s advice on the pH threshold therefore remains unchanged.
Further clinical research is needed into different bedside testing methods and outcome. Small studies found that a magnet tracking system (inserting a magnet in the tip of the tube and scanning to confirm position) may hold promise for future use.11 Further work is also needed by manufacturers of pH indicator papers, given the current problems reported by staff interpreting results in the critical pH range of 4-6.
How will we know when practice has become safer?
The NPSA asked organisations to comply with key actions (recommendations) by September 2011. All incidents of misplaced nasogastric tubes should be reported as never events, and trend data should show a decrease in avoidable harm over time, with fewer cases of misinterpretation of x ray images. Local organisations can also audit processes (using a placement checklist) by checking the notes for 20 consecutive cases in which nasogastric tubes were inserted against best practice. Future national clinical audits should monitor outcomes and processes to see if safety is improving for patients.
Cite this as: BMJ 2011;342:d2586
This is one of a series of BMJ summaries of recommendations to improve patients’ safety, based on reports of safety concerns, incident analysis, and other evidence. The articles highlight the risks of incidents that have the potential for serious harm and are not well known, and for which clear preventive actions are available. Following a Department of Health review in July 2010, the National Patient Safety Agency will be abolished and some of its functions transferred to a patient safety subcommittee of the new NHS Commissioning Board. Reports of incidents are, however, still encouraged at www.npsa.nhs.uk.
Contributors: TL is the guarantor and wrote the first draft, based on NPSA work led by AF, CL, CB, MS-P and colleagues at the NPSA. All authors reviewed the draft.
Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare that all authors had no financial support for the submitted work from anyone other than their employer; no financial relationships with commercial entities that might have an interest in the submitted work; no non-financial interests that may be relevant to the submitted work.
Provenance and peer review: Commissioned; not externally peer reviewed.