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👃 NG tubes
Sizes, pH ≤5.5, and the confirmation rules that make this a Never Event
Feeding through a misplaced nasogastric tube is a Never Event. That is the framing this card is written in, because the harm is not the insertion — it is the first feed into a lung.
There are two valid ways to confirm the tip is in the stomach: aspirate at pH 5.5 or below on CE-marked pH paper, or a chest X-ray read by someone competent to read it for this purpose. Nothing else counts.
Size
| Fine bore, 8Fr | FeedingThe default for feeding and medicines. Has a guidewire — never re-insert the wire with the tube in the patient. |
|---|---|
| 10–12Fr | Feeding, thicker feedsIf an 8Fr keeps blocking. |
| Ryles, 12–16Fr | DrainageObstruction, ileus, "drip and suck". Wide bore, uncomfortable, not for long-term feeding. |
Confirming the tip — what counts
| pH ≤ 5.5 on aspirate | GOCE-marked pH indicator paper for human gastric aspirate. Not litmus. |
|---|---|
| Chest X-ray | GO, if read properlySecond line, or first if no aspirate. Must be requested as an NG check and documented by the person who read it. |
| pH 6 or above | STOPDo not feed. Wait, reposition, consider whether a PPI is raising the pH, re-aspirate. |
| The "whoosh" test | NEVERAuscultating air. Has never been valid and has killed people. |
| Litmus paper | NEVERCannot distinguish gastric from bronchial secretions. |
| Bubbling in water | NEVERAlso the patient talking, coughing normally, or tolerating the tube. None of it confirms anything. |
Practical
| Measure before you pass | NEXNose to Earlobe to Xiphisternum. Note the marking at the nostril and document it. |
|---|---|
| Recheck the position | Before every feedAlso before medicines, after vomiting or coughing, and if the external marking has moved. |
| Do not pass if | Base of skull fractureOr significant mid-face trauma — the tube can enter the cranium. Also caution with varices and recent upper GI surgery. |
If you are not certain, do not feed. An NG tube that is not confirmed is an NG tube that does nothing until it is, and a delayed feed harms nobody in the timescale this decision is made on.
A tube that was in the stomach yesterday is not confirmed today. Position is checked before every single use, not once at insertion — displacement is the commonest route to this Never Event, not misplacement.
The pH rule is national; the process around it is local. Who is signed off to interpret the film, how the X-ray is requested, and what must be documented are set by your trust policy. Find out before you need it, not at 3am.
Source: NHS England Patient Safety Alert NHS/PSA/RE/2016/006 — Nasogastric tube misplacement; NPSA decision trees