11/13/24, 7\:33 PM Guide | NG tube position

NG tube position

Table of contents

Introduction

The ability to safely assess nasogastric (NG) tube placement is a key skill that medical students need to develop. The
assessment of NG tube placement requires a systemic approach and a willingness to ask for senior assistance if unsure, to
prioritise patient safety. The incorrect placement of an NG tube can result in life-threatening complications (e.g. aspiration
pneumonia).
This guide aims to provide you with a systematic approach to con
should NOT be relied upon outside of this setting (always follow local guidelines).

Indications

The most common indications for NG tube insertion include\:
Nasogastric feeding and/or administration of medication (a
Drainage of the upper gastrointestinal tract in conditions such as small bowel obstruction (a larger diameter NG tube -
known as a 'Ryles tube').
When inserting an NG tube for feeding and/or administration of medication you need to con
tube prior to its use. The incorrect placement of an NG tube can result in life-threatening complications (e.g. aspiration
pneumonia).

Methods of con

The two methods of con
Measurement of NG aspirate pH using pH indicator paper
Chest X-ray
Methods which should never be used to con
Auscultation of air insu
Testing the acidity/alkalinity of aspirate using blue litmus paper
Interpreting the absence of respiratory distress as an indicator of correct positioning
Monitoring bubbling at the end of the tube
Observing the appearance of NG tube aspirate

Testing pH of NG aspirate

Con
Gastric content has a low pH (1.5-3.5) whereas respiratory tract secretions have a much higher pH.
² This di
possible to con
(typically 0 - 5.5).
¹
The acceptable pH range for con
hospital guidance. In addition, some hospitals may require a chest X-ray to con
regardless of the NG aspirate results, so always consult your local guidelines.
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Some limitations of pH testing include
Stomach pH can be altered by medications (e.g. proton pump inhibitors)
Obtaining aspirate from NG tubes can be di

Con

If pH testing of NG aspirate is not possible, a chest X-ray can be used to con
Limitations of using a chest X-ray to con
Risk of misinterpretation
Radiation exposure (minimal)
Loss of feeding time (whilst awaiting the X-ray)
Access to chest X-rays is more limited in the community setting

Anatomical landmarks on a chest X-ray

It is essential that you can recognise key anatomical landmarks on a chest X-ray if you are to safely con
using this imaging modality.
The annotated chest X-ray below highlights these key anatomical landmarks including\:
Trachea
Right and left main bronchi
Carina
Diaphragm
Aortic knuckle
The oesophagus itself is often di
medially to the aortic knuckle. The normal oesophagus passes through the diaphragm and enters the stomach at the
gastroesophageal junction (GOJ).
Key anatomical landmarks visible on chest X-ray

Assessing NG tube placement on a chest X-ray

Con
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You should
Patient name, date of birth and unique patient identi
Date and time of the X-ray to make sure you are looking at the appropriate radiograph.
Con
To con
The chest X-ray viewing
The NG tube should remain in the midline down to the level of the diaphragm.
The NG tube should bisect the carina.
The tip of the NG tube should be clearly visible and below the left hemidiaphragm.
The tip of the NG tube should be approximately 10 cm beyond the GOJ (i.e. within the stomach).
If any of the above criteria are not met and/or you have any doubt about the placement of the NG tube you should seek advice
from a senior colleague or discuss with the on-call radiologist.
Incorrect placement of an NG tube
An NG tube can be positioned in the left or right main bronchus but to still appear in the midline (hence why the single
criterion of an NG tube appearing in the midline is not satisfactory evidence to con
An NG tube can curl up on itself, meaning the tip is placed higher than it should be which can result in re
of NG tube contents. This demonstrates the importance of con

Example of correct NG tube placement

The example below meets the criteria of safe NG placement mentioned previously\:
The chest X-ray
The NG tube remains in the midline down to the level of the diaphragm
The NG tube bisects the carina
The tip of the NG tube is clearly visible and below the left hemidiaphragm
The tip of the NG tube is 10 cm beyond the GOJ and therefore is likely to be within the stomach
An example of a correctly positioned NG tube [3]

Examples of incorrect NG tube placement

NG tube placed in the left and right main bronchus
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This chest X-ray shows an NG tube which has entered the trachea, then the left main bronchus before
backwards on itself over into the right main bronchus where the tip can be seen.
If we assess this X-ray using the criteria for correct NG tube placement it is clear that it would not be possible to deem this
placement as safe\:
The chest X-ray view is adequate (YES)
The NG tube remains in the midline down to the level of the diaphragm (NO)
The NG tube bisects the carina (NO)
The tip of the NG tube is clearly visible and below the left hemidiaphragm (NO)
The tip of the NG tube is 10 cm beyond the GOJ and therefore likely to be within the stomach (NO)
An example of an NG tube in the right main bronchus [3]
NG tube placed in the left lung
This chest X-ray demonstrates an NG tube that has entered the trachea, then entered the left main bronchus and then
penetrated through the left lung parenchyma and visceral pleural. The NG tube tip has therefore ended up in the pleural
space (with an associated pneumothorax). This is an extreme example of misplacement, but it is a good example of why an NG
tube tip appearing close to or slightly below the diaphragm alone does not con
If we assess this X-ray using the criteria for correct NG tube placement it is clear that it would not be possible to deem this
placement as safe\:
The chest X-ray view is adequate (YES)
The NG tube remains in the midline down to the level of the diaphragm (NO)
The NG tube bisects the carina (NO)
The tip of the NG tube is clearly visible and below the left hemidiaphragm (NO)
The tip of the NG tube is 10 cm beyond the GOJ and therefore likely to be within the stomach (NO)
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An example of an NG tube in the left lung [3]
Inadequate insertion length
This chest X-ray shows an NG tube that has been inserted into the oesophagus successfully but to an inadequate length. As a
result, although the tip of the NG tube is likely to be within the fundus of the stomach, the aperture through which feed is
excreted is most likely still within the oesophagus. NG tubes which are not inserted to an adequate length can result in
oesophageal re
repeat X-ray to ensure placement was adequate.
If we assess this X-ray using the criteria for correct NG tube placement it is clear that it would not be possible to deem this
placement as safe\:
The chest X-ray view is adequate (YES)
The NG tube remains in the midline down to the level of the diaphragm (YES)
The NG tube bisects the carina (YES)
The tip of the NG tube is clearly visible and below the left hemidiaphragm (YES)
The tip of the NG tube is 10 cm beyond the GOJ and therefore likely to be within the stomach (NO)
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An example of an NG tube not inserted to an adequate length [3]
Di
Sometimes it is very di
interpret, as the example below demonstrates.
If we assess this X-ray using the criteria for correct NG tube placement it is clear that it would not be possible to deem this
placement as safe\:
The chest X-ray view is adequate (YES)
The NG tube remains in the midline down to the level of the diaphragm (YES)
The NG tube bisects the carina (YES)
The tip of the NG tube is clearly visible and below the left hemidiaphragm (NO)
The tip of the NG tube is 10 cm beyond the GOJ and therefore likely to be within the stomach (NO)
If the tip of an NG tube is not clearly visible, you should discuss with the on-call radiologist who may advise\:
Repeating the chest X-ray, possibly with an additional lateral view
Source\: geekymedics.com
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