Nasogastric tube insertion and verification — formative SAQs

SAQ 1 — The verification rule and the deprecated methods (10 marks, 15 minutes)

Stem: A clinical audit on a paediatric ward finds that several nurses are still using the whoosh test to confirm nasogastric tube position before feeds. Outline the accepted bedside verification method, the pH threshold and its physiological basis, the deprecated methods and why each is unsafe, and the action when the pH is above 5.5 or no aspirate can be obtained. [1] [4]

Model answer

The accepted method and the threshold (4 marks). The accepted bedside method is aspirate pH measured with a CE-marked indicator strip. A reading of 5.5 or less confirms gastric placement and is the green light to feed; a reading above 5.5, or no aspirate, means do not feed and obtain a radiograph. The physiological basis is that gastric contents are acidic, with a pH typically between 1 and 5.5, because parietal cells secrete hydrochloric acid, whereas respiratory secretions and small-intestinal contents have a pH of 6 or more. So a strip of pH paper held to a drop of aspirate separates the stomach from the airway, which is exactly the distinction that prevents a feed entering the lung. [4] [6]

The deprecated methods and why each is unsafe (4 marks). The deprecated methods are the whoosh or air-insufflation test, listening over the stomach with a stethoscope while pushing air in; the bubbling test, observing whether air bubbles appear when the tube end is held under water; litmus and blue litmus paper; auscultation used alone; and reliance on the volume or appearance of the aspirate. They are unsafe because none reliably separates a gastric from a respiratory tube: the whoosh sound and the auscultatory bubble transmit across the chest whether the tube is in the stomach or the lung, litmus is too coarse to read in the critical range around 5.5, and the bubbling test can expose staff to secretions. Using any of these as the sole check is itself part of the Never Event. [4] [9]

The action when pH is above 5.5 or there is no aspirate (2 marks). Reposition the tube and re-attempt aspiration once. If the pH is still above 5.5 or aspirate is still absent, request a radiograph that shows the whole course of the tube and its tip below the diaphragm over the stomach, interpret it, and document before any feed. Record the exact pH value, the radiograph result, the length at the naris, and the date and time. [1] [4]

SAQ 2 — A preterm neonate, a difficult insertion, and a Never Event (10 marks, 15 minutes)

Stem: A preterm neonate on the neonatal unit has a nasogastric tube passed for feeding. The first attempt is difficult and the infant then deteriorates with respiratory distress and subcutaneous emphysema at the neck. Separately, on the ward a feed has been given through a tube confirmed only by the whoosh test. Address (a) the most likely complication of the difficult insertion and its immediate management, and (b) why the second event is a Never Event and the ward response. [11] [9]

Model answer

The neonate — complication and immediate management (5 marks). The most likely complication 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 presentation is sudden deterioration, with respiratory distress, drooling, subcutaneous emphysema at the neck, and a pneumothorax, during or just after a difficult insertion. The immediate management is to 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. The tube must not be re-passed, because a second passage enlarges the false passage. In the very preterm or nasal-obstructed neonate an orogastric tube is often preferred precisely to reduce this risk. [11] [5]

The ward event — the Never Event and the response (5 marks). Under the NHS England Never Events framework, the misplacement of a naso- or orogastric tube is a Never Event when feed or medicine is given through a tube whose position has not been confirmed, or has been confirmed only by a deprecated method. Because the whoosh test was retired and cannot reliably separate a gastric from a respiratory tube, feeding after a whoosh-only check meets the definition, regardless of whether the child coughs or a complication follows. The ward response is immediate: stop any further feed, escalate to a senior clinician and to critical care, image the chest, and treat aspiration pneumonia, chemical pneumonitis, a pleural effusion or a pneumothorax on their merits. The event is reported through the local incident system, disclosed to the family honestly and early, and used as the trigger for a review of the unit's verification process, the documentation, and the training, so that the whoosh test is removed from practice and aspirate pH at 5.5 or less becomes the enforced standard. [9] [4]