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]}