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

Accuracy of pH strip testing and pH liquid testing versus standard pH meter of gastric contents in critically ill patients: a diagnostic accuracy study

OBJECTIVE

The utilisation of pH level measurements from gastric contents may indicate the preferred tip position of a nasogastric tube or monitor the efficacy of stress ulcer prophylaxis in critically ill patients. We aimed to determine the accuracy of pH strip (pHS) tests and pH liquid (pHL) tests compared with the standard pH meter (pHM).

DESIGN

Diagnostic accuracy study.

SETTING

Gastric contents from medically critically ill patients.

PARTICIPANTS

In total, 113 gastric samples were collected from 27 critically ill patients.

OUTCOME MEASURE

The level of pH measured by pHM, pHS and pHL.

RESULTS

The pH values measured by pHM, pHS and pHL were 5.83 (IQR 5.12-6.61), 5.50 (IQR 5.00-6.00) and 5.75 (IQR 5.25-6.25), respectively. The pHS test showed greater accuracy, exhibiting a more positive correlation with the standard pHM measurement than the pHL test, with Y=0.95*X+0.56; rho=0.91, p<0.001, and Y=1.09*X - 0.72; rho=0.75, p<0.001, respectively. However, the pHS test demonstrated less agreement with the pHM than the pHL test, with biases of -0.27 versus 0.18, respectively. Noticeably, a slight variation in pHL from the standard pH values was found when we measured gastric contents with a pH lower than 5.

CONCLUSION

Both the pHS and pHL methods were good options for measuring gastric pH in critically ill patients. However, it was advisable to find alternative approaches to the pHL testing method when anticipated gastric acidity levels fall below 5.

TRIAL REGISTRATION NUMBER

TCTR20220530004.

Validating nasogastric tube placement with pH testing: A randomized controlled trial protocol

Background

Enteral nutrition (EN) is preferred when oral feeding is not possible. The use of the Nasogastric Tube (NGT) ensures rapid and low-risk nutrient administration. However, confirming the placement through chest radiography, besides delaying the initiation of nutritional therapy, exposes patients to radiation. The pH test of gastric aspirate provides a quicker check for NGT placement, but its reliability is compromised by challenges related to aspirating gastric secretions.

Study objective

The main objective of this study is to assess the high-performance placement of NGTs for nutritional purposes, optimizing the evaluation of correct insertion through pH testing using an electronic pH meter. Additionally, the study aims to evaluate patient tolerance to the intervention.

Materials and methods

This single-center RCT will include 150 EN candidate patients divided into three groups. Each group will use distinct NGTs, evaluating placement through pH testing and chest radiography for safety. Tolerance, complications related to NGT placement, and costs will be assessed, with data collected anonymously through a secure electronic database.

Ethical considerations

authorization no. 3624, Territorial Ethical Committee Lombardy 5, October 20, 2023.

Implications and perspectives

This protocol introduces innovative technologies, such as advanced NGTs and an electronic pH meter, aiming to optimize enteral nutrition management. This RCT focuses on replacing X-rays as the primary method for verifying NGT placement, thereby reducing costs, time, and patient exposure to radiation. Data analysis may provide insights into managing patients on pH-altering medication. Implementing innovative technologies has the potential to reduce errors and improve economic efficiency and process sustainability.

[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.

Placement of Nasogastric Feeding Tube and Postinsertion Care Review

Insertion and postinsertion care of enteral nasogastric feeding tubes are common procedures in the United States, with more than 1.2 million temporary nasogastric feeding tubes inserted annually. Although there are some evidence-based practice guidelines and recommendations for care of these tubes, variation in practice still exists. Additional research is needed to determine the best methodology for insertion and confirmation of nasogastric feeding tubes. Routine competency and training on feeding tube insertion, enteral nutrition, and postinsertion care is crucial to prevent patient safety events. Variable results have been reported with different technologies; however, radiographic confirmation remains the criterion standard. It is important that health care institutions develop standardized procedures for insertion and confirmation on the basis of evidence-based practices to minimize risks and complications from temporary nasogastric feeding tubes.

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.

Comparison of electromagnetic guided imagery to standard confirmatory methods for ascertaining nasogastric tube placement in children

PURPOSE

Evaluate the accuracy of an electromagnetic device (EMD) guided nasogastric tube (NGT) placement compared with standard confirmation methods. A secondary aim was to determine if EMD guided NGT placement would avert potential pulmonary misplacements of the tube.

DESIGN AND METHODS

Pediatric Intensive Care Unit (PICU) patients were enrolled if they had an NGT order during the study period of April 2014 through December 2016. Patients were included if they were one through 18 years of age. An EMD trained nurse inserted the NGT using EMD guidance. An insertion questionnaire, confirming if the nurse determined the NGT to be gastric per EMD, was completed immediately after NGT placement and before confirmation via either pH testing or radiographic imaging.

RESULTS

Forty-five patients were enrolled in the study. Nurses reported, based on EMD, that 86.7% (n = 39) of placements were gastric. Overall agreement between EMD guided tube placement and pH testing was 58% (n = 26). The marginal distribution was significantly different between the two methods (p = .0029). When compared to radiographic confirmation, sensitivity of the pH method was 32% (95% confidence interval [CI]: 17%-51%) compared with 85% (95% CI 69%-95%) for the EMD method.

CONCLUSIONS

EMD guidance was superior to pH testing when compared with radiographic confirmation of nasogastric tube placement in children.

PRACTICE IMPLICATIONS

EMD guided NGT placement is a potentially viable method for confirming nasogastric tube placement in children when done by appropriately trained clinicians. More research on EMD guided NGT placement in children is needed before any practice recommendation can be made.

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.

Biologically transparent illumination is a safe, fast, and simple technique for detecting the correct position of the nasogastric tube in surgical patients under general anesthesia

The aim of this study was to evaluate the effectiveness of using biologically transparent illumination to detect the correct position of the nasogastric tube in surgical patients. This prospective observational study enrolled 102 patients undergoing general surgeries. In all cases, a nasogastric tube equipped with a biologically transparent illumination catheter was inserted after general anesthesia. The identification of biologically transparent light in the epigastric area either with or without finger pressure indicated that the tube had been successfully inserted into the stomach. X-ray examination was performed to ascertain the tube position and was compared with the findings of the biologically transparent illumination technique. Biologically transparent light was detected in 72 of the 102 patients. In all of these 72 patients, the position of the nasogastric tube in the stomach was confirmed by X-ray examination. The light was not detected in the other 30 patients; X-ray examination showed that the nasogastric tube was positioned in the stomach in 21 of these 30 patients but not in the other 9. The sensitivity and specificity of the illumination were 77.4% and 100%, respectively. The results suggest that biologically transparent illumination is a useful and safe technique for detecting the correct position of the nasogastric tube in surgical patients under general anesthesia. When the BT light cannot be identified, X-ray examination is mandatory to confirm the position of the nasogastric tube.

National Survey of Feeding Tube Verification Practices: An Urgent Call for Auscultation Deimplementation

BACKGROUND

Harm events such as pneumothoraces and pneumonia continue to be associated with feeding tube insertion. Most bedside verification methods are not accurate to discriminate pulmonary from gastrointestinal system. Evidence-based clinical practice guidelines do not support auscultation of feeding tubes in adults, yet auscultation is the most common method used.

OBJECTIVES

Our survey assessed national feeding tube verification practices used by critical care nurses, including progress in auscultation method deimplementation, and stylet reinsertion and cleansing practices.

METHODS

A national survey of 408 critical care nurses was performed.

RESULTS

The majority performed auscultation (311 of 408 [76%]) to verify feeding tube placement. In the final multivariable model, nursing education, facility type, observation of colleagues performing auscultation, and awareness of an institutional policy were associated with auscultation of feeding tubes. Thirty-five percent used enteral access devices to verify initial feeding tube placement. Stylet cleansing methods were variable; 38% of reinserted stylets were not cleansed.

DISCUSSION

Minimal progress has been made in deimplementation of auscultation in the past 7 years despite passive knowledge dissemination in research articles, clinical practice guidelines, and procedure manuals. Although pH measure is used as a first-line feeding tube verification method in the United Kingdom, it is rarely used in the United States. Clinical practice guidelines should be updated to incorporate new research on enteral access systems.

CONCLUSIONS

Tradition-based practices such as auscultation and certain stylet cleansing methods should be deimplemented. A focused interdisciplinary, multifaceted program is needed to deimplement auscultation practice for adult feeding tubes.

Endoscopic management of enteral tubes in adult patients - Part 2: Peri- and post-procedural management. European Society of Gastrointestinal Endoscopy (ESGE) Guideline

ESGE recommends the "pull" technique as the standard method for percutaneous endoscopic gastrostomy (PEG) placement.Strong recommendation, low quality evidence.ESGE recommends the direct percutaneous introducer ("push") technique for PEG placement in cases where the "pull" method is contraindicated, for example in severe esophageal stenosis or in patients with head and neck cancer (HNC) or esophageal cancer.Strong recommendation, low quality evidence.ESGE recommends the intravenous administration of a prophylactic single dose of a beta-lactam antibiotic (or appropriate alternative antibiotic, in the case of allergy) to decrease the risk of post-procedural wound infection.Strong recommendation, moderate quality evidence.ESGE recommends that inadvertent insertion of a nasogastric tube (NGT) into the respiratory tract should be considered a serious but avoidable adverse event (AE).Strong recommendation, low quality evidence.ESGE recommends that each institution should have a dedicated protocol to confirm correct positioning of NGTs placed "blindly" at the patient's bedside; this should include: radiography, pH testing of the aspirate, and end-tidal carbon dioxide monitoring, but not auscultation alone.Strong recommendation, low quality evidence.ESGE recommends confirmation of correct NGT placement by radiography in high-risk patients (intensive care unit [ICU] patients or those with altered consciousness or absent gag/cough reflex).Strong recommendation, low quality evidence.ESGE recommends that EN may be started within 3 - 4 hours after uncomplicated placement of a PEG or PEG-J.Strong recommendation, high quality evidence.ESGE recommends that daily tube mobilization (pushing inward) along with a loose position of the external PEG bumper (1 - 2 cm from the abdominal wall) could mitigate the risk of development of buried bumper syndrome.Strong recommendation, low quality evidence.

Diagnostic accuracy of a pH stick, modified to detect gastric lipase, to confirm the correct placement of nasogastric tubes

Objective

The correct placement of a nasogastric feeding tube is usually confirmed by establishing that an aspirate is acidic using a pH stick. However, antacid medication and achlorhydria can cause false negative pH tests that may delay feeding and increase resource use. The purpose of this study was to evaluate a modified pH stick designed to detect gastric lipase and therefore reduce false negative tests.

Methods

In this prospective observational study, a convenience sample of adult patients who had either gastric and oesophageal samples taken during routine diagnostic gastroscopy (n=97) or bronchial and saliva samples taken during a bronchoscopy (n=106). The samples were tested by blinded observers using the modified and standard pH sticks. The sensitivities and specificities of the two pH sticks in identifying gastric and non-gastric aspirates were compared using the pH cut-off ≤5.5.

Results

The sensitivities of a pH≤5.5 to correctly identify gastric samples were 66% (95% CI 56 to 75) and 68% (95% CI 57 to 77) for the modified and the standard pH, respectively. The specificities were 81% (95% CI 76 to 85) and 79% (95% CI 74 to 84). There were no significant differences in the distribution of the discordant results between the paired gastric and non-gastric samples for both the modified and standard pH sticks at pH≤5.5 (both McNemar’s tests, p≥0.05).

Conclusions

There were no significant differences between the paired modified and standard pH tests for the gastric samples. Due to the limited accuracy of pH sticks, further research is required to identify accurate and cost-effective bedside methods to confirm the correct placement of nasogastric tubes.