A prospective observational study of pH testing to confirm ongoing nasogastric tube position

To measure the reliability of pH testing to confirm ongoing nasogastric tube (NGT) position and to document associated complications.

Confirming NGT position is essential, as use of an incorrectly positioned tube can cause harm. Substantial evidence examines initial confirmation of NGT position, yet limited evidence exists considers NGT displacement which is identified via ongoing NGT position tests. In the NHS, pH testing is recommended to confirm ongoing NGT position; however, there may be an association with excess X-rays and missed enteral nutrition and/or medications.

Prospective observational study using STROBE checklist.

Data collected from medical records of 136 patients with NGTs in a London NHS Trust included pH tests, test results and complications related to ongoing pH tests which failed to confirm the tube was positioned in the stomach, that is, X-rays, and disruptions to enteral nutrition and medication. Cohen's Kappa determined pH test reliability.

Of 1381 pH tests conducted to confirm NGT position, five (0.3%) correctly identified an NGT displacement, and one (0.07%) failed to identify displacement before use. The reliability of ongoing pH tests using Cohen's Kappa was minimal (0.29). Ongoing pH tests that failed to confirm a correctly positioned NGT led to 31 (22.8%) patients having X-rays, 24 (17.6%) missing >10% of prescribed enteral nutrition and 25 (18.4%) missing a critical medication.

Ongoing NGT position testing using pH tests did not prevent the use of a displaced tube, and more than one-fifth of patients required X-rays to confirm a correctly position NGT, contributing to missed medications and enteral nutrition.

Caution should be used when confirming ongoing NGT position with a pH test. Future guidelines should balance the risk of using a displaced tube with potential delays to nutrition and/or medication. More research is needed to explore alternative methods of ongoing NGT position testing.