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Please wait while the page loadsClinical Skills · Children's Nursing
A clearer guide to NG tubes in children, including the parts students get asked about most: NEX, pH testing, and what to do if you cannot get aspirate.
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Student note
An NG tube is a soft tube that goes from the nose into the stomach. In children it is used for feeding, medicines, and sometimes to drain the stomach. The most important part of the skill is proving it is really in the stomach before anything goes down it.
When and why a child might need one
Feeding
Medication
Decompression
NEX — Nose, Ear, Xiphisternum
NEX is the quick measuring rule students often get taught first. It stands for Nose, Ear, Xiphisternum, and it gives you an estimated insertion length:
Clinical pearl
NEX is a guide, not proof. A tube can still be too short and sit in the food pipe instead of the stomach, which is why pH testing of aspirate matters so much. Some trusts use slightly modified versions of NEX to improve accuracy, so always follow local policy.
Step by step — paediatric specific
This is a common exam question — and it matters clinically
The physics
The simple version is this: a small syringe pulls much harder. That stronger suction can flatten the fine tube against the stomach lining, which makes aspirate harder to get and can irritate the stomach.
The clinical implication
A 20 ml, 50 ml, or 60 ml syringe gives gentler suction. That makes it more likely you will actually get aspirate for pH testing without collapsing the tube.
The rule
Do not use a syringe smaller than 20 ml to aspirate from an NG tube. Many trusts use 50 ml or 60 ml as standard. A very small syringe can make you think the tube is misplaced when the problem is actually the syringe.
Exam pearl
If you get asked why a large syringe is used, the short student answer is: it creates gentler suction, so the tube is less likely to collapse and you are more likely to get aspirate safely.
First-line method: pH testing of gastric aspirate
Safe to use
pH ≤ 5.5
Confirms stomach placement. Document the pH reading, the tube length at the nostril, and the time of the check.
Do not use
pH > 5.5
Could be in the food pipe, airway, or beyond the stomach. Do not give anything down the tube. Escalate.
Things that affect pH readings
Antacids / PPIs / H2 blockers
These medicines can make the stomach less acidic, so the pH may be above 5.5 even when the tube is in the right place. Those children often need X-ray confirmation.
Recent feed
Milk and formula make the stomach contents less acidic. Wait at least 1 hour after a feed before testing, or try before the next feed is due.
Continuous feeds
The pH may stay above 5.5 while feed is running all the time. A planned feeding break or an X-ray may be needed.
Using litmus paper
Litmus paper is not accurate enough for this. Use approved pH indicator paper with 0.5 graduations.
Unsafe methods — never use these
Clinical pearl
The whoosh test, which means pushing air down the tube and listening over the stomach, is no longer accepted practice. Air in the lung can sound very similar to air in the stomach, so it is not safe enough to trust. Placement should be checked with pH testing of aspirate or, if needed, X-ray confirmation.
When to re-confirm and which size to use
Placement must be re-confirmed:
Clinical pearl
Always document the external tube length at the nostril when you first confirm placement. This gives you a simple reference point. If the length changes, assume the tube may have moved and re-test before using it.
Tube size guide
| Age / weight | French gauge (Fr) |
|---|---|
| Premature neonate | 5 Fr |
| Term neonate | 6 Fr |
| Infant (1–12 months) | 6–8 Fr |
| Toddler (1–3 years) | 8 Fr |
| Child (3–10 years) | 8–10 Fr |
| Adolescent | 10–12 Fr |
Complications & red flags
Exam pearl
The most common questions are: why do we use a large syringe, what pH confirms stomach placement, and why is the whoosh test unsafe. Examiners also want to hear that you would never use the tube until placement is confirmed and that you would escalate if pH is above 5.5 or you still cannot get aspirate.
“What if you can't get aspirate?”
This comes up a lot in OSCEs. Know the order: turn the patient onto their left side, sit them more upright if possible, move the tube in or out by 1 to 2 cm, then wait 15 to 30 minutes and try again. If none of that works, request an X-ray as a last resort. Never use the tube until placement is confirmed.
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