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Please wait while the page loadsClinical Skills · Children's Nursing
How to insert, confirm placement, and safely use a nasogastric tube in paediatric patients — including why syringe size matters and what to do when you can't get aspirate.
NG tubes are used in paediatrics for feeding (when a child can't take oral nutrition safely), medication administration, and gastric decompression. Getting placement confirmation right is safety-critical — a misplaced tube can deliver feed into the lungs. This guide covers insertion technique, the pH testing method, and common placement problems.
Feeding
Medication
Decompression
The NEX measurement (Nose–Ear–Xiphisternum) estimates the insertion length:
Clinical pearl
NEX measurement is a guide, not a guarantee. Studies show it can underestimate the required length, placing the tip in the oesophagus rather than the stomach. This is why pH testing of aspirate is essential — you cannot rely on length alone. Some trusts now use modified NEX (nose to ear, then ear to a point midway between xiphisternum and umbilicus) for improved accuracy.
Step by step — paediatric specific
This is a common exam question — and it matters clinically
The physics
Pressure = Force ÷ Area. A smaller syringe (e.g. 5ml or 10ml) has a smaller cross-sectional area of the plunger. When you pull back on a small syringe, the same hand force generates much higher negative pressure inside the tube. This can cause the fine-bore tube to collapse against the gastric mucosa, making it impossible to get aspirate — and potentially damaging the stomach lining.
The clinical implication
A 20ml, 50ml, or 60ml syringe has a larger plunger area, so the same hand force produces gentler, lower-pressure suction. This is enough to draw up gastric contents without collapsing the tube or suctioning the mucosa. It gives you a better chance of actually obtaining aspirate for pH testing.
The rule
Never use a syringe smaller than 20ml to aspirate from an NG tube. Most trusts specify 50ml or 60ml as standard. A smaller syringe risks tube collapse, mucosal damage, inability to obtain aspirate, and a false assumption that the tube is misplaced when it may actually be correctly positioned.
Exam pearl
If asked “why do we use a large syringe?” — your answer is about pressure physics: a larger barrel area means lower negative pressure for the same applied force, preventing tube collapse and mucosal injury. Examiners want to hear that you understand the mechanism, not just “because policy says so.”
First-line method: pH testing of gastric aspirate
Safe to use
pH ≤ 5.5
Confirms gastric placement. Document pH reading, tube length at nostril, and time of check.
Do not use
pH > 5.5
Could be in the oesophagus, respiratory tract, or intestine. Do not administer anything. Escalate.
Antacids / PPIs / H2 blockers
Raise gastric pH — may give readings >5.5 even with correct placement. These children often need X-ray confirmation.
Recent feed
Milk and formula buffer stomach acid. Wait at least 1 hour after a feed before testing, or aspirate before the next feed.
Continuous feeds
Gastric pH may never drop below 5.5. Consider a planned break in feeding to allow pH to fall, or use X-ray.
Using litmus paper
Litmus paper is not accurate enough. Only CE-marked pH indicator paper with 0.5 graduations should be used.
The “whoosh test” (injecting air and listening over the stomach with a stethoscope) was historically common but is no longer accepted practice. Air injected into a tube sitting in the lung can sound identical to air in the stomach. The NPSA issued a patient safety alert (2011) banning this method after fatal incidents where feed was delivered into the lungs. pH testing of aspirate or X-ray confirmation are the only safe methods.
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 reference — if the length changes, the tube has migrated and must be re-tested before use. Mark it on the nursing care plan and record it at every check.
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
Exam pearl
The most common questions: “Why do we use a large syringe?” (pressure physics — larger barrel = lower suction pressure), “What pH confirms gastric placement?” (≤5.5), and “Why don't we use the whoosh test?” (NPSA safety alert — it cannot distinguish gastric from pulmonary placement). Examiners also look for correct NEX measurement technique, confirmation that you would not use the tube until placement is verified, and that you know to escalate when pH is >5.5 or aspirate cannot be obtained.
“What if you can't get aspirate?”
This comes up a lot in OSCEs. Know the order: turn the patient onto their left side (the stomach sits to the left of the body, so gravity pools gastric contents around the tube tip), sit them more upright if possible, advance or withdraw the tube by 1–2cm, then wait 15–30 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. Never inject air to try and free the tube — that's no longer safe practice.