Nasogastric tube placement confirmation: where we are and where we should be heading

Abstract

Background:

Insertion of a tube via the nasal passage is a common procedure which has been practiced for many years. There are various ways to assess the position of the nasogastric tube (NGT).

Objectives:

The objective of this study was to discuss the advantages and limitations of each method of NGT placement confirmation, to identify gaps in literature, and provide suggestions for future research.

Methods:

A search was performed with Pubmed, CINAHL, and Embase. The following keywords were used: “nasogastric,” “tube,” “placement,” “insertion,” and “measurement.” The results were narrowed down to those with full text available, published in the English language, those published within the last 10 years, and those studies done in the adult population. The reference lists of those articles were also referred to and relevant articles were retrieved. A final 26 relevant articles were included in this review, including six that were published more than 10 years ago but still relevant in this review.

Results:

A method to confirm NGT placement that is accurate, affordable, does not require gastric aspirates, and is able to be used not only upon insertion but also at regular intervals is lacking.

Conclusions:

This article provides a summary of the different methods of NGT placement confirmation and discusses their advantages and limitations. Gaps in literature and suggestions for future research were also deliberated.

Keywords

Nasogastric tube placement confirmation position

Introduction

Nasogastric tubes (NGTs) have been around for a long time, with the first account of their insertion being in the seventeenth century. Their first use was solely for providing nutrition.¹ Currently, NGTs are also used for other indications such as the administration of medications, gastric decompression, or gastric irrigation.¹

Methods to confirm the placement of the NGT have also drastically changed over the years. According to a nursing text by Scott in the 1930s, placement of the NGT into the larynx was considered rare and the asphyxiating reaction when the NGT is placed into the airways would make incorrect positioning obvious.² In the same text, the key to determining correct NGT position in the stomach was to ensure that the marking on the tube was aligned with the opening of the nostril, and variation among individuals was considered negligible.² Now, we know that spotting a malposition of the NGT to the lung simply by witnessing severe respiratory distress is a myth even in patients with an intact gag reflex.³ In fact it is possible for the NGT to be inserted into the airway without any adverse reaction from the patient and for the patient to be asymptomatic until several hours later and after multiple feedings.⁴ It was also reported that the NGT may be displaced up or downwards even when the external portion remains anchored by taping.⁵

In the last ten years, new methods of NGT insertion and placement confirmation have surfaced. However, there are still incidents of wrong placement leading to detrimental effects. In 2014, the Singapore Nursing Board reported a case of death resulting from the NGT being misplaced in the right bronchus.⁶ In less extreme situations, NGTs which did not pass the esophagogastric junction (resting in the esophagus) increased the risk of aspiration of feeds into the lungs.⁷

Methods of NGT placement confirmation reported in the literature include X-ray,⁵ observation for presence of bubbling,⁸ auscultation with insufflation of air,⁵ litmus paper test,⁹ pH paper test,^5,8–13 use of biochemical markers,^14,15 capnography/colorimetric capnometry,¹⁶ ultrasound,^17–20 electromagnetic (EM) tracing,^21–25 visualization,²⁶ and manometer techniques.^27,28 This paper aims to discuss the advantages and limitations of these methods and identify directions for future research.

Methods

A search was performed using the databases of Pubmed, CINAHL, and Embase. The following keywords were used: “nasogastric,” “tube,” “placement,” “insertion,” “confirmation,” “complications,” “safety,” and “measurement.” The results were narrowed down to those published in the English language within the last 10 years and performed among the adult population; 50 articles were found. The reference lists of these articles were referred to and relevant articles were included. Novel methods of NGT placement checks that were used without confirmation with any established methods were excluded in this review.

A final 26 articles were included in this review, including six that were published more than 10 years ago but still relevant.

Discussion

The gold standard

X-ray

X-rays are currently the gold standard for NGT placement confirmation because they can visualize the course of the NGT.⁵ However, it is infeasible, unsafe, and not cost effective to perform an X-ray and expose the patient to radiation before each NGT use. Despite being the gold standard, it is not foolproof. Between 2005 and 2010, 45% of all cases of harm caused by a misplaced NGT reported by the National Patient Safety Agency were due to misinterpreted X-rays.²⁹

First-line method for bedside checking of NGT placement

pH testing

This is the first-line method for NGT placement confirmation recommended by the National Patient Safety Agency in the United Kingdom (UK).¹⁰ According to data collected by Saint Louis School of Nursing, whereby >1200 samples were collected over >8 years, it was found that gastric pH usually falls within 1–5, while intestinal or respiratory pH is usually ≥7.⁸ Therefore, aspirates with pH ≤ 5 would likely indicate a gastric placement.⁸

In a published review, data from studies examining the pH of gastric aspirates were collated, and the sensitivity and specificity for each pH cutoff point calculated.⁹ The cutoff point with the highest sensitivity and specificity for a gastric placement was pH ≤ 5.5.⁹ This cutoff point showed a sensitivity (95% confidence interval (CI)) of 0.89 (0.82–0.94), and a specificity (95% CI) of 0.87 (0.81–0.93).⁹ However, only one paper studied this cutoff point. Other cutoff points such as pH ≤ 4.0, pH ≤ 5.9 or 6, pH ≤ 6.5, pH ≤ 7.0, and pH ≤ 7.9 produced either a low sensitivity or specificity.⁹ Therefore, it is reasonable to use a cutoff point of pH ≤ 5 or ≤5.5 to determine a gastric placement of the NGT.^5,9 However, this method has its limitations.

Firstly, obtaining an aspirate is not always possible. In a study by Boeykens et al.,¹¹ an aspirate could only be immediately obtained in 48.6% of the patients. In another 33.5%, aspirates could be obtained after additional measures such as insufflation of air into the NGT, lateral-positioning of the patient and reattempting after an hour.¹¹ Thus in 33.5% of the patients, this would result in delayed feeding, and in 18.4%, it would be impossible to use this method due to the lack of aspirates. In another study, the incidence of not obtaining an aspirate was as high as 69%.¹²

Another limitation would be the presence of other factors which alter gastric pH. Associating pH with NGT tip location was studied under specific conditions.⁸ Aspirates were collected after patients were fasted for at least four hours.⁸ For patients on continuous feeding, the feeds will likely interfere with pH of the gastric aspirates. Hence, pH ≤ 5 may not apply to these patients.

Use of medications also alters gastric pH. Metheny and Titler reported that mean gastric pH was higher when acid inhibiting agents were used than when they were not (4.34±0.14 vs. 3.33±0.2).⁸ Similarly, Boeykens et al. found that those taking H2 receptor antagonists or proton pump inhibitors (PPIs) have an average pH of 4.6 while those not taking these drugs have an average pH of 3.5.¹¹ Although average pH was still <5 with acid lowering drugs; the drug class matters as well. PPIs are said to increase the number of patients with pH > 6.¹¹ In a study performed among patients in the intensive care unit (ICU), patients received pantoprazole or famotidine and continuous feeding for 93% of the patient days.¹² Gastric aspirates were checked 6 hourly and the pH was 6.0–7.9, 64% of the time.¹² This suggests that a large percentage of ICU patients have false negative results using the pH method.

Furthermore, a case was reported whereby the NGT aspirate of a patient with right tonsillar squamous cell carcinoma showed a pH of 4.5 even though the NGT was in the chest.¹³ Pathophysiology of acidic lung aspirates is not well studied but it may be due to chronic aspiration of saliva and food particles, and/or bacterial superinfection.¹³

Therefore this method is not foolproof and not always feasible.

Other methods of confirming NGT placement

Observation of bubbles

Observing for bubbles when the exposed end of the NGT is in water assumes that if the NGT is in the respiratory tract, bubbling will occur upon exhalation.⁸ However, there were instances where bubbling did not occur when tubes were in the lung, presumably because the ports were occluded by pulmonary tissue.⁸ Furthermore, the stomach can contain gas; hence bubbling may occur even if it were positioned correctly, making it difficult for differentiation.⁸

Auscultation with insufflation of air

A stethoscope is placed over the epigastrium to listen for a whoosh sound as 10–30 mL of air is insufflated through the NGT.⁵ However, sounds may be transmitted to the epigastrium whether the tube is positioned in the lung, esophagus, stomach, duodenum, or proximal jejunum.⁴ In three case studies whereby the NGTs were thought to be in the stomach following air insufflation, they were in the lung, causing death in two out of three patients.⁴ In another study, 15 out of 16 NGTs were incorrectly identified as being in the stomach when auscultation method was used.³⁰ Similarly, a study performed among advanced practice nurses did not yield promising results for the accuracy of this method.¹¹ Although auscultation lacks evidence, its advantage is that NGT aspirates are not required. Therefore, it is still used at the bedside, in the absence of an aspirate.

Litmus paper

It was thought that if a blue litmus paper turned pink upon contact with NGT aspirates, it would indicate an acidic aspirate suggesting a gastric placement.⁹ However, blue litmus paper turns pink even when pH is 6 or 7, a pH level that is unable to distinguish between gastric or bronchial aspirates.⁹

Biochemical markers

The use of bilirubin, pepsin, and trypsin levels has been used together with pH to confirm placement.^14,15

It was found that mean pH levels in the lungs (7.73) and intestine (7.35) were significantly higher than mean pH levels in the stomach (3.90; p < 0.001 for each comparison), while mean bilirubin levels in the lungs (0.08 mg/dL) and stomach (1.28 mg/dL) were significantly lower than mean bilirubin levels in the intestine (12.73 mg/dL; p < 0.001 for each).¹⁴ By visually inspecting the distribution overlap and mean differences by NGT placement, results were dichotomized so that a combination of pH and bilirubin values could be used to develop a predictive algorithm.¹⁴ pH > 5 and bilirubin < 5 mg/dL correctly identified all respiratory cases, while pH > 5 with bilirubin ≥ 5 mg/dL correctly identified three quarters of the intestinal cases.¹⁴ pH ≤ 5 with bilirubin < 5 mg/dL correctly identified more than two thirds of the gastric cases.¹⁴

In another study, effectiveness of using pH ≤ 6, pepsin ≥ 100 µg/mL, and trypsin ≤ 30 µg/mL in predicting gastric placement of the NGT was evaluated.¹⁵ Using a logistic regression equation with all three variables to differentiate between respiratory and gastrointestinal placement, it was possible to correctly classify 100% of the respiratory cases and 93.4% of the gastrointestinal cases.¹⁵ Another equation used to differentiate between gastric and intestinal sites was able to correctly classify 91.2% of the gastric cases and 91.5% of the intestinal cases.¹⁵

Although these methods seem an improvement to the pH method, levels of pepsin and trypsin need to be tested at the lab, as there are no bedside methods for testing of these biochemical markers.¹⁵ Hence, it is not feasible to be used as a method to check the NGT placement before each feeding as time will be required for samples to be sent to the lab and the results reported back to the nurse. This potentially delays feeding time and increases healthcare costs.

Capnography/colorimetric capnometry

Capnography is the continuous analysis and recording of the carbon dioxide (CO₂) levels using infrared technology.¹⁶ The result is expressed in partial pressure in millimeters of mercury and a flow waveform will be detected.¹⁶ Colorimetric capnometry uses phenolsulfonephthalein impregnated pH sensitive filter paper that changes from purple to yellow in the presence of CO₂.¹⁶ As the lungs exhale CO₂, it would be expected for capnography/colorimetric capnometry to detect CO₂ if the NGT were placed in the lungs instead of the stomach.

A meta-analysis was performed for nine trials, eight of which involved 456 NGT placements that investigated the diagnostic accuracy of CO₂ detection in detecting airway intubation and differentiating respiratory and GI placement of the NGT.¹⁶ The last trial involved 195 gastric tube insertions in 130 patients and compared the diagnostic accuracy of the colorimetric CO₂ detector and capnography to detect feeding tube placement.¹⁶

To determine the placement of the NGT in the trachea, four trials placed the NGT into the already placed endotracheal tube (ETT) and used a colorimetric meter to detect CO₂ levels. Another two trials placed the NGT into the ETT or tracheostomy and used capnography to obtain gas samples. Both methods were found to detect a tracheal placement with 100% accuracy.¹⁶

When it came to differentiating between gastric and trachea placement, the data from seven studies were used. The pooled data found that the sensitivity, specificity, and positive and negative likelihood ratios were 0.99, 0.99, 57.30, and 0.05, respectively.¹⁶

One trial compared the use of capnography versus colorimetric capnometry in detecting respiratory intubation among 130 mechanically ventilated adult patients (195 gastric tube insertions) in the ICU.¹⁶ Insertion failures with detection of CO₂ occurred in 27% of instances, and this was successfully detected with the colorimetric indicator (within seconds) for all insertions.¹⁶ Therefore Chau et al. concluded that a colorimetric device was as accurate as capnography for detecting CO₂ during placement of NGTs.¹⁶

This seems like a promising method of NGT placement confirmation, especially when NGT aspirates are not required. However, these studies were performed upon insertion of NGT and none were performed subsequently before each feeding or at regular intervals for patients on continuous feeding. One study suggested that false positive results from colorimetric capnometry could be related to contamination of the capnometer from the reflux of gastric contents.³¹ Therefore, it is unsure if the use of this method will be suitable after the tube has been used for feeding and gastric contents are present within the NGT. Furthermore, ingesting carbonated beverages or medications such as sodium bicarbonate could potentially result in the presence of CO₂ in the stomach.³²

Ultrasound

The use of ultrasound at the neck can confirm NGT position in the esophagus and its use at the epigastrium can confirm a stomach placement.¹⁷ However, the esophagus can only be viewed via the ultrasound if it is in a laterotracheal position, and this was reported to only occur in about 50% of the population.¹⁷

Similarly, one study only managed to visualize the NGT in the neck area in 83% of the patients post NGT insertion and the NGT was only visualized in the stomach in 12.8% of the patients.¹⁸ In the remaining patients where there was difficulty in viewing the gastro-esophageal junction, 40 mL of normal saline and 10 mL of air was injected into the NGT and if fogging is seen via the ultrasound, it is said to be in the stomach.¹⁸ Fogging was seen in 70.2% of the patients and in the other 17%, visualization of the NGT was impaired due to artefacts produced by air.¹⁸ The practice of fogging is not ideal as it requires an introduction of fluids into the NGT before its placement is confirmed. Additionally, when compared to chest X-rays, this study found ultrasound to have a sensitivity of only 86.4% and a specificity of 66.7%.¹⁸

To counter the problem of introducing fluids before NGT placement has been confirmed, a study used a color Doppler ultrasound whereby a color Doppler flow signal would be detected by a probe placed at the epigastrium when 20 mL of air is injected into the NGT.¹⁹ The sensitivity was 90% (95% CI 83.7%–96.2%) and specificity 80% (95% CI 55.2%–100%).¹⁹ However, false positives may occur due to breathing artefacts of patients or if the NGTs were in the lower esophagus and the injected air flows from the esophagus into the stomach.¹⁹

One other study used the ultrasound not only to check the placement of NGT post insertion but to obtain real time imaging of the NGT’s passage through the esophagus.²⁰ A guide wire was used to insert the NGT in this study in order for it to be seen ultrasonographically as hyperechoic.²⁰ It was successful in the majority of patients; however, in 5.3% the esophagus could not be seen by ultrasonography.²⁰ Furthermore, the position of the tip of the NGT was not determined via ultrasound but via an abdominal X-ray.²⁰ Therefore, this method only showed the passage of the NGT through the esophagus but could not ensure that the tip was inside the stomach. Gok et al. also mentioned difficulty in determining if the NGT is in the trachea in intubated patients.²⁰

Electromagnetic (EM) tracing

This method uses real-time computer navigation to direct and verify NGT placement.²¹ The tip of the NGT contains an electromagnetic transmitter which produces a location signal.²¹ Placed at the patient’s xiphoid process, a receiver receives the signal from the tip of the NGT and tracks the movement of the NGT during insertion.²¹ The location and path of the tube is shown on a bedside monitor.²¹

Compared to the use of X-rays, Taylor et al. found EM trace interpretation of position to be correct with 100% agreement.²² Similarly, Powers et al. found 97.4% agreement between EM traces and X-rays with contrast (whereby the contrast was injected via the NGT before the X-ray) and 86.9% agreement with EM traces and X-rays without contrast.²³ Furthermore, the EM trace when the NGT is inserted into the lung is very different from when it is positioned in the stomach.²² This can prevent the possibly deadly results of a malpositioning of NGT into the lungs. In the use of feeding tubes with stylets, EM tracing was found to reduce the rates of pneumothorax.²⁴ Furthermore, using EM trace instead of X-ray confirmation can also prevent delay in feeding.²⁵

However, EM trace only confirms tube placement during insertion and cannot make subsequent confirmation. Additionally, 17% of NGTs required injection of water to allow guidewire manipulation during insertion.²² Sterile water is acidic and may give a false low pH when the user is checking the pH of the NGT aspirates post insertion.²²

Visualization technology

The Kangaroo^TM feeding tube with iris technology allows for real-time visualization of anatomical landmarks through a camera during NGT insertion.²⁶ Only one study using this technology, with a population of 20 unconscious patients, has been found.²⁶ It was able to identify a trachea placement during insertion, allowing the NGT to be withdrawn and reinserted.²⁶ It also allowed for easy visualization of the gastric mucosa for 18 patients (90%).²⁶ In one patient, only the gastroesophageal junction was identified and in another, visualization was poor.²⁶ This technology proved less useful for subsequent checking, with only a reliable visualization of the gastric mucosa in 60% of patients within the first week of enteral nutrition and the percentage dropped to 33% after the first week.²⁶

Manometer technique

In 35 intubated patients, the cuff pressure of the ETT was increased to 40 cmH₂O before insertion of the NGT to fully inflate the cuff and maximize contact between the tracheal wall and cuff.²⁷ Then, an NGT was inserted with laryngoscope guidance into either the tracheal or esophagus.²⁷ Five patients were excluded in the analysis as the NGT was unable to advance through the trachea with the inflated ETT cuff.²⁷ In the remaining patients, it was found that the cuff pressure increased by 28±8 cmH₂O if the NGT passed through the ETT cuff and it remained elevated as long as the NGT was left in place.²⁷ On the other hand, inserting the NGT into the esophagus resulted in an increased cuff pressure by only 1±1 cmH₂O.²⁷ Thus, an increase of >10 cmH₂O in cuff pressure could detect endotracheal malpositioning of the NGT with 100% sensitivity and specificity.²⁷

Not only can the manometer be used during insertion, it may be used to check NGT placement at regular intervals as well. A study was performed among a group of patients who were intubated for surgery.²⁸ After tracheal intubation, the NGT was inserted blindly.²⁸ When the manometer was attached to the NGT, if there was little variation in pressure during mechanical ventilation, and manual compression of the epigastric area with a compression depth of approximately 3–5 cm showed a notable pressure change on the manometer, it was considered a gastric placement.²⁸ If the manometer showed a biphasic pressure change that synchronizes with the ventilator, it was considered to be a tracheal placement.²⁸ Subsequently, position of the NGT was checked by using a fiberscope and the final confirmation of placement within the stomach was made by the surgeon using manual palpation of the tube after laparotomy.²⁸

Overall, the percentage of misplacements was 22.3% and the incidence of airway misplacement was 2.9%.²⁸ These events were detected by the manometer technique prior to fiberoscopy.²⁸ The study concluded that the manometer method had 100% sensitivity and specificity in predicting a correct gastric placement and airway misplacement.²⁸

These studies suggest a promising method of NGT placement confirmation among critically ill and mechanically ventilated patients since this group of patients are potentially unsuitable candidates for the pH method (refer previous section). However, this method may not be generalizable to the rest of the population who are not mechanically ventilated.

Table 1 provides a summary of the advantages and disadvantages of each method of NGT placement confirmation.

Table 1.

Advantages and limitations of different methods of confirming NGT placement.

Method of checking NGT placement	Authors	Advantages	Disadvantages
X-ray	Turgay and Khorshid⁵	Does not require NGT aspirates. Considered the gold standard. Able to visualize the course of the NGT.	Exposes the patient to radiation. Relatively more costly. Not feasible or safe to be performed before each use of the NGT for patients on bolus feeding, or at regular intervals for patients on continuous feeding. Not foolproof as there are still cases of misinterpreted X-rays.²⁹
pH testing	Metheny and Titler,⁸ Fernandez et al.,⁹ Boeykens et al.,¹¹ Conner and Carver,¹² and Sellers¹³	Easy to carry out. Not costly. Able to distinguish between gastric, intestinal and respiratory placement.⁸	Requires NGT aspirates. Time of last feed can alter the gastric pH and this method may be less useful for those on continuous feeding. Medications may alter the gastric pH, especially acid lowering medications such as H2 antagonist, antacids and proton pump inhibitors.⁸
Observation of bubbles	Metheny and Titler⁸	Easy to carry out. Not costly. Does not require NGT aspirates.	Unable to differentiate a gastric or respiratory placement from the presence or absence of bubbles.⁸ No longer recommended.
Auscultation with insufflation of air	Metheny et al.,⁴ Boeykens et al.,¹¹ and Neumann et al.³⁰	Does not require NGT aspirates. Not costly.	Insufflated air can transmit sounds to the epigastrium regardless of whether the tube is positioned in the lung, esophagus, stomach, duodenum, or proximal jejunum.⁴ No longer recommended.
Litmus paper	Fernandez et al.⁹	Easy to carry out. Not costly.	Requires NGT aspirates. Unable to distinguish between the gastric or bronchial aspirates as the blue litmus paper turns pink as long as the pH is less than 7.⁹ No longer recommended.
Biochemical markers with pH testing	Metheny et al.^14,15	Use of biochemical markers improve the accuracy of pH testing. pH and bilirubin levels were able to correctly identify all respiratory placements.¹⁴ pH, pepsin, and trypsin levels were able to correctly identify all respiratory placements and a high percentage of gastric placements.¹⁵	Requires NGT aspirates. Not widely studied. No bedside method of testing pepsin and trypsin;¹⁵ thus it is not feasible and may be costly. pH levels obtained will also be altered by feeds and medications and this method has similar limitations as the pH testing.
Capnography/ colorimetric capnometry	Chau et al.,¹⁶ Elpernet al.,³¹ and Shelly³²	Does not require NGT aspirates. Able to detect tracheal placement with a very high accuracy.¹⁶	Could result in false positive results related to the contamination of the capnometer due to gastric reflux.³¹ Unsure if it is suitable for subsequent checks after the NGT has been used. Ingesting carbonated beverages or medications such as sodium bicarbonate could potentially result in the presence of carbon dioxide in the stomach.³²
Ultrasound	Petitpas et al.,¹⁷ Kim et al.,¹⁸ Wong et al.,¹⁹ Gok et al.²⁰	Does not require NGT aspirates. Able to visualize that the NGT is in the esophagus and not the trachea, and able to confirm a stomach placement.¹⁷ May be used to obtain real time image of the NGT’s passage through the esophagus.²⁰	Esophagus can only be viewed via the ultrasound if the esophagus is in a laterotracheal position.¹⁷ Difficult to determine if the NGT is in the trachea in intubated patients.²⁰ May require elaborate training for the users. May be relatively more costly.
Electromagnetic tracing	Powers et al.,²¹ Taylor et al.,²² and Powers et al.²³ Koopmann et al.,²⁴ and Bearet al.²⁵	Does not require NGT aspirates. Might be more accurate than plain X-rays in determining a NGT placement.²³ Able to tell a lung placement during insertion.²²	Not able to confirm the placement of NGT before each feeding. 17% of polyurethane tubes required injection of water to allow guide-wire manipulation during the insertion of the NGT which is not ideal as sterile water or saline is acidic and may give a falsely low pH when the user is checking the pH of the gastric secretions post insertion.²² May require elaborate training for the users. May be relatively more costly.
Visualization of anatomical landmarks using a camera	Carrara et al.²⁶	Does not require NGT aspirates. Able to tell exact location of the NGT during insertion, preventing lung placement. Easy gastric mucosa visualization for 90% of the patients.	Although rare, poor visualization is possible. Not as useful for subsequent checking as only able to reliably visualize the gastric mucosa in 60% of patients within the first week of enteral nutrition and 33% after the first week. May require elaborate training for the users. May be relatively more costly.
Manometer technique	Fuchs et al. and Hsieh et al.^27,28	Does not require NGT aspirates. 100% sensitivity and specificity in predicting a correct gastric placement and in predicting an airway misplacement.²⁸ May be used to aid in the process of insertion of NGT.²⁷ Not costly.	May not be generalizable to the rest of the population who are not mechanically ventilated.

Implications for future practice

The new visualization technology by Kangaroo^TM seems a promising start, whereby visualization of the gastric mucosa is possible for subsequent checking. This would be useful for both hospitalized patients and for those requiring NGT insertion in the community. However, at present, the technology is not always reliable after feeding has commenced.

The use of the manometer could also be potentially beneficial to critically ill patients who are mechanically ventilated as such patients are unsuitable candidates of the pH method. Unfortunately, there is still a lack of studies to confirm the use of this method in such patients.

Implications for future research

Research could be channeled to the improvement of the visualization technology to make it reliable for placement confirmation after feeding. Moreover, further studies could be performed to verify the sensitivity and specificity of the manometer technique in critically ill and mechanically ventilated patients as reported in the literature.

Time will be required for such improvements to take place. A more feasible step at the moment could be to improve the current pH method by increasing the probability of obtaining an aspirate. Given that the gastric mucosa produces 1.2–1.5 L of gastric juice per day,³³ it is unclear why there are still incidences where it is impossible to obtain gastric aspirates from the NGT. Perhaps the position of the NGT tip in the stomach in relation to the patient’s position could affect the probability to retrieve gastric aspirates. On the other hand, the stomach could also be viewed as a deflatable container whereby if all the air has been aspirated then the gastric juices should be able to be obtained regardless of the location of the tip of the NGT in the stomach. Other possible factors affecting the success of obtaining the gastric aspirates could also be the length and width of the NGT. If the probability of obtaining an aspirate is increased, the pH method could be feasible in a larger group of patients, benefitting them while other methods of placement confirmation are being perfected.

Conclusion

Much progress has been made in the area of NGT placement confirmation over the years. However, a perfect method has yet to be found. This causes frustration for the nurses and caregivers of the patients requiring the care of the NGT. Further research into an ideal method that is accurate, affordable, easy to use, able to minimize discomfort that may result from having to reinsert a wrongly positioned NGT, and is able to be used during insertion and at regular intervals could benefit this population.

Footnotes

Declaration of Conflicting Interests

The authors declare that there are no conflicts of interest.

Funding

This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

References

Phillips

Nasogastric tubes: an historical context. Medsurg Nurs 2006; 15: 84–88.

Scott

DH.

Modern professional nursing. Vol. 3. London: Caxton, 1936, p.306.

Curtis

Caring for adult patients who require nasogastric feeding tubes. Nurs Stand 2013; 27: 47–56.

Metheny

Wehrle

Wiersema

et al . Testing feeding tube placement: auscultation vs. pH method. Am J Nurs 1998; 98: 37–43.

Turgay

Khorshid

Effectiveness of the auscultatory and pH methods in predicting feeding tube placement. J Clin Nurs 2010; 19: 1553–1559.

Singapore Nursing Board. Annual report 2014. Singapore: Singapore Nursing Board, 2015.

De Oliveira Santos

SCV

Woith

de Freitas

MIP

et al . Methods to determine the internal length of nasogastric feeding tubes: an integrative review. Intl J Nurs Stud 2016; 61: 95–103.

Metheny

Titler

Assessing placement of feeding tubes. Am J Nurs 2001; 101: 36–46.

Fernandez

Chau

Thompson

et al . Accuracy of biochemical markers for predicting nasogastric tube placement in adults: a systematic review of diagnostic studies. Int J Nurs Stud 2010; 47: 1037–1046.

10.

Cole

Improving the documentation of nasogastric tube insertion and adherence to local enteral nutrition guidelines. BMJ Qual Improv Rep 2015; 4: u203207–w1513.

11.

Boeykens

Steeman

Duysburgh

Reliability of pH measurement and the auscultatory method to confirm the position of a nasogastric tube. Int J Nurs Stud 2014; 51: 1427.

12.

Conner

Carver

The role of gastric pH testing with small-bore feeding tubes: in the intensive care unit. Dimensions Crit Care Nurs 2005; 24: 210–214.

13.

Sellers

CK.

False-positive pH aspirates after nasogastric tube insertion in head and neck tumour. BMJ Case Rep 2012: bcr2012006591.

14.

Metheny

Stewart

Smith

et al . pH and concentration of bilirubin in feeding tube aspirates as predictors of tube placement. Nurs Res 1999; 48: 189–197.

15.

Metheny

Stewart

Smith

et al . pH and concentrations of pepsin and trypsin in feeding tube aspirates as predictors of tube placement. J Parenter Enteral Nutr 1997; 21: 279–285.

16.

Chau

Thompson

et al . Use of end-tidal carbon dioxide detection to determine correct placement of nasogastric tube: a meta-analysis. Int J Nurs Stud 2011; 48: 513–521.

17.

Petitpas

Kerforne

Lacroix

et al . Comment on “A novel approach to confirming nasogastric tube placement in the ED”. Am J Emerg Med 2012; 30: 631–632.

18.

Kim

Jeong

et al . The effectiveness of ultrasonography in verifying the placement of a nasogastric tube in patients with low consciousness at an emergency center. Scand J Trauma Resusc Emerg Med 2012; 20: 38–38.

19.

Wong

Chan

Wong

et al . Using color flow detection of air insufflation to improve accuracy in verifying nasogastric tube position. Am J Emerg Med 2017; 35: 333–336.

20.

Gok

Kilicaslan

Yosunkaya

Ultrasound-guided nasogastric feeding tube placement in critical care patients. Nutr Clin Pract 2015; 30: 257.

21.

Powers

Fischer

Ziemba-Davis

et al . Elimination of radiographic confirmation for small-bowel feeding tubes in critical care. Am J Crit Care 2013, 22: 521–527.

22.

Taylor

Allan

McWilliam

et al . Confirming nasogastric tube position with electromagnetic tracking versus pH or X-ray and tube radio-opacity. Br J Nurs 2014; 23: 352–358.

23.

Powers

Luebbehusen

Spitzer

et al . Verification of an electromagnetic placement device compared with abdominal radiograph to predict accuracy of feeding tube placement. J Parenter Enteral Nutr 2011; 35: 535–539.

24.

Koopmann

Kudsk

Szotkowski

et al . A team-based protocol and electromagnetic technology eliminate feeding tube placement complications. Ann Surg 2011; 253: 297–302.

25.

Bear

Champion

Lei

et al . Use of an electromagnetic device compared with chest x-ray to confirm nasogastric feeding tube position in critical care. J Parenter Enteral Nutr 2016; 40: 581.

26.

Carrara

Mizzi

Cozzi

et al . SUN-PP254: Kangaroo feeding tube with iris technology reduces the risk of pulmonary misplacement in critically ill patients. Clin Nutr 2015; 34: S117–S118.

27.

Fuchs Schummer Giesser et al . Detection of tracheal malpositioning of nasogastric tubes using endotracheal cuff pressure measurement. Acta Anaesthesiol Scand 2007; 51: 1245–1249.

28.

Hsieh

Chen

et al . To characterize the incidence of airway misplacement of nasogastric tubes in anesthetized intubated patients by using a manometer technique. J Clin Monit Comput 2017; 31: 443–448.

29.

National Patient Safety Agency. 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.

30.

Neumann

Meyer

Dutton

et al . Hold that X-ray: aspirate pH and auscultation prove enteral tube placement. J Clin Gastroenterol 1995; 20: 293–295.

31.

Elpern

Killeen

Talla

et al . Capnometry and air insufflation for assessing initial placement of gastric tubes. Am J Crit Care 2007; 16: 544–549.

32.

Shelly

LM.

Capnometry vs pH testing in nasogastric tube placement. Gastrointest Nurs 2011; 9: 30–33.

33.

Sircus

Hightower

Keeton

et al . Human digestive system, https://global.britannica.com/science/human-digestive-system/Gastric-secretion (2015, accessed 14 September 2016).