Selecting pH cut-offs for the safe verification of nasogastric feeding tube placement: a decision analytical modelling approach

Checking nasogastric tube safety in children cared for in the community: a re-examination of the evidence base

Nasogastric tube feeding is generally considered safe provided a nasogastric aspirate with a pH ≤5.5, which indicates that the end of tube is correctly located in the stomach, can be obtained. When this is not possible, hospital attendance or admission is usually required so that an X-ray can be undertaken to check the tube's position. This practice is based on an interpretation of the evidence that places undue importance on nasogastric aspirate pH testing before every use of a tube that is already in place, with potential negative consequences for children cared for in the community and their families. Following a re-examination of the evidence base, a revised approach is proposed in this article: when a child has a tube in place, provided its position has been confirmed as correct on initial placement using aspirate pH testing, nurses can use checks other than aspirate pH testing, alongside their clinical judgement, to determine whether it is safe and appropriate to use the tube. This proposed revised approach would reduce delayed or missed administration of fluids, feeds and medicines and enable more children to remain at home.

Nasogastric tube insertion length measurement and tip verification in adults: a narrative review

Nasogastric feeding tube insertion is a common but invasive procedure most often blindly placed by nurses in acute and chronic care settings. Although usually not harmful, serious and fatal complications with misplacement still occur and variation in practice still exists. These tubes can be used for drainage or administration of fluids, drugs and/or enteral feeding. During blind insertion, it is important to achieve correct tip position of the tube ideally reaching the body of the stomach. If the insertion length is too short, the tip and/or distal side-openings at the end of the tube can be located in the esophagus increasing the risk of aspiration (pneumonia). Conversely, when the insertion length is too long, the tube might kink in the stomach, curl upwards into the esophagus or enter the duodenum. Studies have demonstrated that the most frequently used technique to determine insertion length (the nose-earlobe-xiphoid method) is too short a distance; new safer methods should be used and further more robust evidence is needed. After blind placement, verifying correct gastric tip positioning is of major importance to avoid serious and sometimes lethal complications.

[Safe position check of gastric tubes: an often underestimated topic to prevent possible severe complications]

The insertion of a gastric tube in the operating room (OR) or in an intensive care unit (ICU) is a routine procedure. Although the tube is often inserted by nursing staff, the indications and selection of the procedure for position control remain the physician's responsibility. For immediate position control, the injection of air through the inserted tube with simultaneous auscultation of the epigastrium is probably the most simple and common clinical method. A typical "bubbling" is often regarded as a sufficiently reliable sign of correct gastric tube position. This procedure can be described as a routine standard both in the OR and the ICU; however, numerous examples from clinical practice and quality reviews show gastric tube mispositioning in esophageal, bronchial, pulmonary or even pleural positions in individual cases. Since auscultation findings are misinterpreted as tracheal, bronchial, or pleural secretions, mispositioning may remain undetected. In addition, adequate documentation of the procedure is lacking. In the worst case, hyperosmolar tube feeding occurs via the malpositioned tube into the lungs or pleural space causing subsequent severe pneumonia or pleuritis, which is often fatal for the patient outcome. In contrast to many other similar procedures in intensive care medicine, such as the installation of central venous catheters or endotracheal intubation, to our knowledge there is no uniform standard for forensic verification of the correct position after gastric tube positioning. The present work provides an overview of existing practices and the scientific background for confirmation of gastric tube positioning without ionizing radiation.

Fibre-optic, electronic pH test device compared with current NHS guidance to confirm nasogastric tube placement

The clinical objectives of this prospective, random, convenience series were: 1. Compare a novel fibre-optic pH test device (NGPOD) to gastric aspirate and pH testing for nasogastric tube (NGT) confirmation. 2. Determine if the new device reduces the need for chest radiography (chest X-ray, CXR).

Methods

Recruitment of patients over the age of 18, requiring NGT feeding.Exclusion criteria: oesophageal gastrointestinal surgery within 3 months; all those with partial or total gastrectomy; bleeding gastric and duodenal ulcers; gastric cancer; those with oesophageal varices; those considered to be inappropriate.The index test, NGPOD, comprises a fine, flexible fibre-optic sensor passed down the NGT, then connected to an electronic device. A green light indicates pH ≤5.5, and a red light if pH is >5.5.The reference test is withdrawal of gastric aspirate and testing with universal pH indicator strips then comparison to a colour chart. Second-line testing is establishing NGT position by CXR or subjective clinical assessment (SCA) in intensive care unit (ICU).

Results

The analysed data set contained 174 subjects who had undergone 496 tests, 96 initial and 400 repeat NGT checks.For all patients, NGPOD can reduce the need for CXR or SCA by 21.2%.In ICU, NGPOD can reduce the need for CXR or SCA by 24.5%.When performing initial tests, immediately after tube placement, NGPOD can reduce the need for CXR or SCA in 61% of patients.With repeat testing, NGPOD can reduce the need to progress to CXR or SCA in 16% of tests.

Conclusions

The objective, yes-no result delivered by NGPOD, eliminates the subjective reading of a pH strip colour change, reducing the subjective element. The index test has the opportunity to reduce risk, improve safety and decrease the numbers of patients requiring X-ray. It, therefore, has the potential to reduce never events associated with NGT misplacement.

The accuracy of methods for determining the internal length of a nasogastric tube in adult patients: a systematic review

BACKGROUND

Blind insertion of nasogastric (NG) tubes is performed for several reasons: nutrition and medication administration, gastric aspiration/decompression, and other, diagnostic reasons. Accidental intraesophageal and intestinal placement is common, and increases the risk of serious complications. Therefore, accurate determination of the internal length of the NG tube before placement is considered a prerequisite for achieving correct gastric positioning.

OBJECTIVES

We aimed to identify, assess, and summarize the evidence on the accuracy of methods for determining the internal length of an NG tube in adults.

METHODS

Cochrane Library, Excerpta Medica database (EMBASE), PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Web of Science were searched up to 31 January, 2022. Studies were eligible when reporting data on the accuracy of methods for determining internal NG tube length in adults. Study selection, risk-of-bias assessment, and data extraction were performed independently by 2 investigators. Risk-of-bias was assessed using the Cochrane Risk-of-Bias Tool and the Joanna Briggs Institute Critical Appraisal Checklist for Cross Sectional Studies. A narrative synthesis of the results was then conducted.

RESULTS

Twelve articles were included in this review. All studies were observational, cross-sectional in nature, except for 1 randomized controlled trial. Ten methods for determining the internal length of an NG tube were described. Correctly positioned NG tubes ranged from 13% to 99%. Results showed that the tip of the nose-earlobe-xiphoid distance (NEX) + 10 cm (mean: 59.9-60.7 cm) and (NEX × 0.38696) + 30.37 + 6 cm (mean: 56.6-56.7 cm) could potentially result in accuracy as high as 97.4% and 99.0%, respectively.

CONCLUSIONS

Current data do not provide conclusive evidence of 100% accuracy in finding a correctly placed NG tube when using a method for determining the internal length. Blind placement, using any of the documented methods, cannot be considered safe without additional verification of tube tip positioning. Furthermore, using any of these 10 methods does not reduce the risk of pulmonary intubation.This systematic review was registered at https://www.crd.york.ac.uk/PROSPERO/ as CRD42021243180.

Inadvertent placement of a nasogastric tube following traumatic nasal tube intubation

Adequate nutrition is necessary in head and neck surgery. Enteral feeding via a nasogastric tube is often required due to the altered anatomy and to allow sufficient intraoral healing. Insertion of a nasogastric tube is commonly performed without complication and confirmation of its position by a number of different methods. Incorrect positioning can cause significant morbidity with associated mortality. This case report describes the inadvertent placement of a nasogastric tube in a patient with a mandibular squamous cell carcinoma, into the abdominal cavity following a failed traumatic nasal tube intubation. Chest radiography and auscultation failed to identify the abnormal position with subsequent commencement of feeds for a number of days. Following a laporotomy and insertion of abdominal drains, the patient recovered and was discharged from hospital. To prevent recurrence, it is suggested that direct laryngoscopy or direct visualisation of the upper aspect be performed.

Development and validation of ester impregnated pH strips for locating nasogastric feeding tubes in the stomach-a multicentre prospective diagnostic performance study

BACKGROUND

NG (nasogastric) tubes are used worldwide as a means to provide enteral nutrition. Testing the pH of tube aspirates prior to feeding is commonly used to verify tube location before feeding or medication. A pH at or lower than 5.5 was taken as evidence for stomach intubation. However, the existing standard pH strips lack sensitivity, especially in patients receiving feeding and antacids medication. We developed and validated a first-generation ester-impregnated pH strip test to improve the accuracy towards gastric placements in adult population receiving routine NG-tube feeding. The sensitivity was improved by its augmentation with the action of human gastric lipase (HGL), an enzyme specific to the stomach.

METHODS

We carried out a multi-centred, prospective, two-gate diagnostic accuracy study on patients who require routine NG-tube feeding in 10 NHS hospitals comparing the sensitivity of the novel pH strip to the standard pH test, using either chest X-rays or, in its absence, clinical observation of the absence of adverse events as the reference standard. We also tested the novel pH strips in lung aspirates from patients undergoing oesophageal cancer surgeries using visual inspection as the reference standard. We simulated health economics using a decision analytic model and carried out adoption studies to understand its route to commercialisation. The primary end point is the sensitivity of novel and standard pH tests at the recommended pH cut-off of 5.5.

RESULTS

A total of 6400 ester-impregnated pH strips were prepared based on an ISO13485 quality management system. A total of 376 gastric samples were collected from adult patients in 10 NHS hospitals who were receiving routine NG-tube feeding. The sensitivities of the standard and novel pH tests were respectively 49.2% (95% CI 44.1‑54.3%) and 70.2% (95% CI 65.6‑74.8%) under pH cut-off of 5.5 and the novel test has a lung specificity of 89.5% (95% CI 79.6%, 99.4%). Our simulation showed that using the novel test can potentially save 132 unnecessary chest X-rays per check per every 1000 eligible patients, or direct savings of £4034 to the NHS.

CONCLUSIONS

The novel pH test correctly identified significantly more patients with tubes located inside the stomach compared to the standard pH test used widely by the NHS.

TRIAL REGISTRATION

http://www.isrctn.com/ISRCTN11170249 , Registered 21 June 2017-retrospectively registered.

Ongoing pH testing to confirm nasogastric tube position before feeding to reduce the risk of adverse outcomes in adult and paediatric patients: A systematic literature review

BACKGROUND & AIMS

There is no agreed gold standard method to confirm nasogastric tube position before every use. However, many global guidelines recommend testing the pH of gastric aspirates obtained from an NGT before each use. This study aims to determine whether ongoing pH testing has been shown to reduce adverse events. Secondary aims are to determine how frequently aspirates can be obtained, and how often pH correctly confirms ongoing NGT tip position.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed and protocol was published on PROSPERO. Keywords were used to search PubMed, Embase, CENTRAL, CINAHL and MEDLINE. Article assessment for inclusion was completed by two independent authors and risk of bias was assessed using ROBINS-I.

RESULTS

The systematic search and review methodology was followed due to wide variety and high risk of bias in the included studies. One full study and five abstracts met inclusion criteria for the primary aim. The full article contained one instance where pH testing and external NGT length together identified a misplaced NGT. The abstracts identified missed or delayed feeds and medications, and frequent unnecessary X-rays, as negative outcomes of ongoing pH testing. Ten full studies and one conference abstract addressed the secondary aims, but the studies varied widely which prevented meta-analysis and made it difficult to draw conclusions.

CONCLUSIONS

This review confirmed that ongoing pH testing is based on expert opinion due to limited evidence. More primary research is required to determine the clinical impact of ongoing pH testing to confirm NGT position.

X-ray checks of NG tube position: a case for guided tube placement

OBJECTIVES

Checking nasogastric (NG) tube position by X-ray is too late to prevent 1.5% of blind tube placements entering the lung and results in delays to feeding and drugs. We audit the safety of the tube position and delay incurred by X-ray.

METHODS

From Radiology reports, we determined whether tube position was safe for feeding, factors associated with an X-ray request and the time delay from X-ray request to that report. For tubes misplaced into the lung, the distance from the carina to tube tip was measured and compared with that from published records of guided tube placement.

RESULTS

From 1 July 2019 to 30 June 2020, 1934 X-rays were done to check NG tube position in 891 patients. Gastric placement was confirmed in 85% but, because of tube proximity to the oesophagus, only 73% were deemed safe to feed. The 2.2% of tubes reported to be in the lung were a median of 18 cm beyond the carina compared to 12 cm and 0 cm for electromagnetic and direct vision methods of guided placement. X-ray checks delayed feed and drug treatment by >2 h in 51% of placements and 33% of patients required >3 X-rays during their enteral episode.

CONCLUSION

X-ray checks are common and detect a high percentage of unsafe tube placements, leading to repeated X-ray and delayed delivery of drugs and nutrition. Interpretation can be difficult even when following standard national criteria and post-placement X-ray cannot prevent deep lung placement. Guided or combined methods of confirming tube placement should be investigated.

ADVANCES IN KNOWLEDGE

Reports included 27.5% of placements as unsafe, 2.2% in the lung at a median depth of 18 cm beyond the carina and too late to prevent 7 pneumothoraces. X-rays were repeated >3 times in 33% of patients over their enteral course and we are associated with clinically significant delays to drug treatment (and nutrition) in 51%; combined methods of tube confirmation or guided placement may be safer and more efficient.

Nasogastric Tube Feeding in Older Patients: A Review of Current Practice and Challenges Faced

Nasogastric tube feeding is an essential way of delivering enteral nutrition when the oral route is insufficient or unsafe. Malnutrition is recognised as a reversible factor for sarcopenia and frailty. It is therefore crucial that malnutrition is treated in older inpatients who have dysphagia and require enteral nutrition. Despite five National Patient Safety Alerts since 2005, “Never Events” related to nasogastric feeding persist. In addition to placement errors, current practice often leads to delays in feeding, which subsequently result in worse patient outcomes. It is crucial that tube placement is confirmed accurately and in a timely way. Medical advancements in this area have been slow to find a solution which meets this need. In this paper, we provide an updated review on the current use of feeding nasogastric tubes in the older population, the issues associated with confirming correct placement, and innovative solutions for improving safety and outcomes in older patients.

Nutritional Support in the Intensive Care Unit: Implications for Nursing Care From Evidence-Based Guidelines and Supporting Literature

Several nursing practices are related to oral, enteral, or parenteral feeding on the intensive care unit. Nurses are the group of health care professionals who provide 24-hour care for patients. Therefore, they play a key role in not only identifying nutritional problems but also in ensuring the success of nutritional therapy by implementing evidence-based feeding protocols and ongoing care for (par)enteral access devices. Having an up-to-date evidence-based knowledge about nutritional support can increase safety and quality of care and can contribute to better outcomes. In this narrative review, the most recent European intensive care unit nutrition guidelines and related research are highlighted, and where appropriate, specific applications for nursing practice are described.

Accuracy of the corrected nose-earlobe-xiphoid distance formula for determining nasogastric feeding tube insertion length in intensive care unit patients: A prospective observational study

BACKGROUND

As nasogastric feeding tube insertion is a frequently applied, non-risk-free nursing technique, a high level of evidence-based nursing care is required. Little evidence is available regarding the accurate determination of the insertion length of nasogastric feeding tubes. The method of using the nose-earlobe-xiphoid distance as measurement is inadequate and not supported by evidence. Findings from a recent randomized trial led to an alternative calculation: the corrected nose-earlobe-xiphoid distance formula: (nose-earlobe-xiphoid distance × 0.38696) + 30.37 + 6 cm.

OBJECTIVES

To test the accuracy of the corrected nose-earlobe-xiphoid distance formula for determining the required nasogastric feeding tube insertion length in adults admitted on an intensive care unit and to investigate the probability to successfully obtain gastric aspirate for pH measurement.

DESIGN

Prospective, single-center observational study.

PARTICIPANTS AND METHODS

Adult intensive care unit patients in a general hospital (N = 218) needing a small-bore nasogastric feeding tube were included between March and September 2018. Correct tip positioning was defined as a tube tip located > 3 cm under the lower esophageal sphincter. Tip positioning was verified using X-ray.

RESULTS

All nasogastric feeding tube tips were correctly positioned > 3 cm under the lower esophageal sphincter. The chance of successfully obtaining gastric aspirate within 2 h after placement of the tube was 77.9%.

CONCLUSIONS

With all tips positioned > 3 cm in the stomach and zero tubes migrating back into the esophagus, the corrected nose-earlobe-xiphoid distance formula can be considered a more accurate method to determine nasogastric feeding tube insertion length.

Study to determine the likely accuracy of pH testing to confirm nasogastric tube placement

Objective

To establish the likely accuracy of pH testing to identify gastric aspirates at different pH cut-offs to confirm nasogastric tube placement.

Methods

This prospective observational study included a convenience sample of adult patients who had two (one fresh and one frozen) gastric and oesophageal samples taken during gastroscopy or two bronchial and saliva samples taken during bronchoscopy. The degree of observer agreement for the pH of fresh and frozen samples was indicted by kappa (k) statistics. The sensitivities and specificities at pH ≤5.5 and the area under the receiver operating characteristics (ROC) curve at different pH cut-offs were calculated to identify gastric and non-gastric aspirates.

Results

Ninety-seven patients had a gastroscopy, 106 a bronchoscopy. There was complete agreement between observers in 57/92 (62%) of the paired fresh and frozen gastric samples (k=0.496, 95% CI 0.364 to 0.627). The sensitivity of a pH ≤5.5 to correctly identify gastric samples was 68% (95% CI 57 to 77) and the specificity was 79% (95% CI 74 to 84). The overall accuracy to correctly classify samples was between 76% and 77%, regardless of whether patients were taking antacids or not. The area under the ROC curve at different pH cut-offs was 0.74.

Conclusion

The diagnostic accuracy of pH ≤5.5 to differentiate gastric from non-gastric samples was low, regardless of whether patients were taking antacids or not. Due to the limited accuracy of the pH sticks and the operators’ ability to differentiate colorimetric results, there is an urgent need to identify more accurate and safer methods to confirm correct placement of nasogastric tubes.

Usability study of pH strips for nasogastric tube placement

AIMS

(1) To model the process of use and usability of pH strips (2) to identify, through simulation studies, the likelihood of misreading pH strips, and to assess professional's acceptance, trust and perceived usability of pH strips.

METHODS

This study was undertaken in four phases and used a mixed method approach (an audit, a semi-structured interview, a survey and simulation study). The three months audit was of 24 patients, the semi-structured interview was performed with 19 health professionals and informed the process of use of pH strips. A survey of 134 professionals and novices explored the likelihood of misinterpreting pH strips. Standardised questionnaires were used to assess professionals perceived usability, trust and acceptance of pH strip use in a simulated study.

RESULTS

The audit found that in 45.7% of the cases aspiration could not be achieved, and that 54% of the NG-tube insertions required x-ray confirmation. None of those interviewed had received formal training on pH strips use. In the simulated study, participants made up to 11.15% errors in reading the strips with important implications for decision making regarding NG tube placement. No difference was identified between professionals and novices in their likelihood of misinterpreting the pH value of the strips. Whilst the overall experience of usage is poor (47.3%), health professionals gave a positive level of trust in both the interview (62.6%) and the survey (68.7%) and acceptance (interview group 65.1%, survey group 74.7%). They also reported anxiety in the use of strips (interview group 29.7%, survey group 49.7%).

CONCLUSIONS

Significant errors occur when using pH strips in a simulated study. Manufacturers should consider developing new pH strips, specifically designed for bedside use, that are more usable and less likely to be misread.