Introduction
Nasogastric tube (NGT) insertion is a core clinical skills OSCE station. You must demonstrate safe technique, correct position verification, and recognition of misplacement. Pulmonary placement of an NG tube is a Never Event — pH testing and CXR confirmation exist to prevent it.
💎 Clinical Pearl
Always tell the patient what you are doing at each step. Ask them to swallow as you advance the tube past the pharynx — swallowing closes the larynx and guides the tube into the oesophagus.
Indications
| Indication | Example |
|---|---|
| Enteral feeding | Patients unable to swallow (stroke, unconscious) |
| Drug administration | Unable to swallow tablets |
| Gastric decompression | Post-operative ileus, small bowel obstruction |
| Gastric lavage | Certain overdoses (rare, specialist decision) |
| Aspiration of gastric contents | Monitoring post-surgery |
Contraindications
- Base of skull fracture (risk of intracranial placement via cribriform plate)
- Oesophageal varices or oesophageal stricture (relative contraindication)
- Blocked or deviated nasal passage (use other nostril)
- Coagulopathy (relative — proceed with caution)
Equipment
- NG tube (size 8-12 Fr for feeding; 14-16 Fr for drainage)
- Lubricating gel (water-soluble)
- 50 mL enteral syringe
- pH indicator paper (range 0-6; must be CE-marked for enteral use)
- Adhesive tape and securement device
- Gloves, apron, kidney dish, glass of water with straw
- Pen torch (to check oropharynx)
Measuring the Length
Measure the external length required before insertion:
NEX measurement: Nose to Earlobe to Xiphisternum
Add 10 cm. Mark this point on the tube.
Procedure
- 1Introduce yourself, confirm patient identity, explain procedure, obtain verbal consent
- 2Sit the patient upright (45-90 degrees) with head slightly flexed (chin to chest)
- 3Check which nostril is clearer (patient breathes through each nostril separately)
- 4Perform hand hygiene and don gloves and apron
- 5Measure and mark the tube using NEX method
- 6Lubricate the tip of the tube generously with water-soluble gel
- 7Insert the tube along the floor of the nasal passage (not upward — the floor is horizontal)
- 8Advance gently; at approximately 10-15 cm you will reach the nasopharynx — ask patient to sip water and swallow as you advance. Advance with each swallow.
- 9Continue advancing to the marked length
- 10If patient coughs persistently, becomes cyanosed, or resists, STOP — check with a pen torch for coiling in oropharynx; do not force
⚠️ Red Flag
If the patient coughs, gags excessively, or you see the tube coiling in the oropharynx, withdraw and start again. Never advance a tube against significant resistance.
Confirming Position — Safe Approach
Step 1: pH of Aspirate
- Attach a 50 mL enteral syringe and aspirate gastric contents
- Smear aspirate on CE-marked pH indicator paper
- pH 1-5.5 = gastric position confirmed = SAFE to use
| pH | Interpretation |
|---|---|
| 1-5.5 | Gastric — safe |
| 6 or above | Pulmonary, oesophageal, or duodenal — do NOT use; confirm with CXR |
Step 2: Chest X-Ray (If pH Unavailable or Equivocal)
On CXR, the tube should:
- Follow the midline down the oesophagus
- Cross to the left at the carina (into the oesophagus, not a bronchus)
- Have the tip in the stomach (below the diaphragm, to the left of the spine)
- The tip should be at least 10 cm below the gastro-oesophageal junction
⚠️ Red Flag
Methods NOT accepted for confirmation: auscultation of air (the "whoosh test" — unreliable and has caused deaths), checking if the tube bubbles in water (unreliable). Only pH and CXR are accepted in NHS practice.
Securing and Documenting
- Secure the tube with adhesive tape to the nose and cheek
- Document: date, time, length inserted, pH result, CXR result (if performed), who confirmed position
- Position must be re-confirmed after each use, after vomiting or coughing fits, and if the tube appears to have moved
"How do you confirm nasogastric tube position safely?"
The primary method is aspiration of gastric contents and testing with CE-marked pH indicator paper. A pH of 5.5 or below confirms gastric position. If no aspirate is obtained or pH is 6 or above, a chest X-ray is required before the tube is used. Neither the whoosh test (auscultating for air) nor placing the tube end in water are accepted as safe confirmation methods in NHS guidance.
"What is the NEX measurement and why is it used?"
NEX (Nose-Earlobe-Xiphisternum) is the standardised method for estimating the length of tube needed to reach the stomach. The tube is measured from the tip of the nose to the earlobe, then from the earlobe to the xiphisternum. Ten centimetres is added to this measurement. This ensures the tip sits in the body of the stomach, below the gastro-oesophageal junction.
"What are the contraindications to nasogastric tube insertion?"
Absolute contraindications include base of skull fracture (risk of intracranial tube placement through the cribriform plate — use an orogastric tube instead) and oesophageal obstruction. Relative contraindications include severe coagulopathy, oesophageal varices, and recent oesophageal or gastric surgery. A blocked nasal passage is a practical contraindication — use the other nostril.
"What should you do if the patient coughs persistently during NG tube insertion?"
Stop advancing the tube immediately. Coughing suggests the tube may be in the larynx or trachea. Ask the patient to take a few deep breaths. Check the oropharynx with a pen torch for coiling. Withdraw the tube to the nasopharynx and reattempt, ensuring the patient swallows as the tube is advanced through the pharynx. If the tube consistently enters the airway, consider whether the patient has an impaired swallow or reduced laryngeal reflexes, and seek senior advice.
Related guides: Venepuncture and Cannulation OSCE | Urinary Catheterisation OSCE | A&E Assessment OSCE