Nasogastric tube insertion and verification — branching viva

Opening — can we feed after a whoosh test?

Examiner: A ward nurse has just confirmed a child's nasogastric tube with the whoosh test and asks whether the feed can go down. What is the correct verification method, what is the threshold, and why is the whoosh test unsafe? [1] [3]

Candidate (model): The correct bedside verification is aspirate pH measured with a CE-marked indicator strip, and the threshold is 5.5 or less: a reading at or below 5.5 confirms gastric placement and is the green light to feed. The physiological basis is that gastric contents are acidic, typically pH 1 to 5.5, because parietal cells secrete hydrochloric acid, while respiratory secretions and small-intestinal contents have a pH of 6 or more; the strip separates the stomach from the airway, which is the distinction that stops a feed entering the lung. The whoosh test is unsafe because the sound of insufflated air transmits across the chest whether the tube is in the stomach or the bronchus, so it cannot reliably separate the two. It was retired for that reason, and using it as the sole check is itself part of the Never Event. So the feed must not go down; the nurse aspirates and tests the pH, and feeds only at 5.5 or less, or escalates to a radiograph. [3] [4]

Branch 1 — teaching the team

Examiner: How do you make this the enforced standard on the ward, not just one clinician's preference? [9]

Candidate (model): I treat it as a system, not a personal habit. The unit adopts aspirate pH at 5.5 or less as the only accepted bedside method, removes the whoosh test and the other deprecated methods from the procedure and the documentation, and trains every clinician who places or feeds down a tube. The documentation forces the discipline: each entry records the method, the exact pH value, the radiograph result if used, the length at the naris, and the date and time, so a tube verified by a whoosh test simply cannot be signed off. I add a re-verification rule before every feed and after any event that could move the tube, and I report any breach through the incident system and feed it back. [1] [9]

Branch 2 — the preterm neonate who deteriorated

Examiner: Now a preterm neonate on the unit had a difficult nasogastric tube insertion and has just deteriorated with respiratory distress and subcutaneous emphysema at the neck. What has happened, and what do you do? [11]

Candidate (model): The most likely event is a traumatic pharyngo-oesophageal perforation. In the neonate the posterior pharyngeal wall and the cricopharyngeal region are fragile, and forceful or repeated insertion can create a false passage through the wall, sending the tube into the mediastinum or pleura; the signature is sudden deterioration with respiratory distress, drooling, subcutaneous emphysema, and a pneumothorax during or just after a difficult insertion. I withdraw the tube, escalate to neonatology and surgery, obtain a radiograph, start broad-spectrum antibiotics and supportive care, and arrange surgical review for a confirmed perforation. Critically, I do not re-pass the tube, because a second passage enlarges the false passage. In this age group I would usually prefer an orogastric tube in the first place, precisely to reduce this risk. [11] [6]

Branch 3 — the intubated infant with no aspirate

Examiner: An intubated, sedated infant has had the tube replaced after extubation. No aspirate can be obtained despite repositioning. The registrar proposes to record the external length and feed. How do you respond? [4]

Candidate (model): I would not feed. An absent aspirate is never a licence to feed, and this is the child least able to signal misplacement: intubated and sedated, the infant cannot cough, splutter, or complain, so the verifier is the only safety barrier. The external length does not answer the question of where the tip lies, because the tube can coil in the mouth or oesophagus with a normal external length, or sit in the airway. The correct action is to obtain a radiograph that shows the whole course of the tube and its tip below the diaphragm over the stomach, interpret it, document it, and only then feed. The principle is that the more helpless the patient, the stricter the verification. [4] [6]

Branch 4 — acid suppression and the false high reading

Examiner: A child on a proton-pump inhibitor reads pH 6. The registrar argues that, because the child is on acid suppression, a 6 can be accepted as gastric. How do you answer? [4]

Candidate (model): I agree that acid suppression raises the gastric pH and increases the proportion of readings above 5.5, so the tube may well be in the stomach. But I disagree with the conclusion. The rule bends toward more imaging, never toward a looser threshold: a pH above 5.5 still means do not feed, and I obtain a radiograph. Accepting a 6 as gastric would remove the one barrier that the whole system relies on, and the rate of high readings in a stable child on acid suppression should prompt a review of the verification strategy, not a relaxation of the cut-off. [4] [6]

Closing — the principles examiners reward

Examiner: Give me the three principles you would want every registrar to remember. [1] [9]

Candidate (model): First, aspirate pH of 5.5 or less is the green light to feed, and above 5.5 or no aspirate means stop and obtain a radiograph; the exact number is recorded, not a tick. Second, the whoosh test, the bubbling test, litmus paper and auscultation alone are retired because they have killed children, and using any of them as the sole check is a Never Event. Third, the position is re-verified before every feed and every medicine, and after any event that could move the tube, retching, vomiting, coughing, retaping, transfer, or extubation, because a tube that has moved may now lie in the airway. [1] [9]