NHS safety agency issues guidance on nasogastric tubes

The National Patient Safety Agency (NPSA) advice on reducingthe harm caused by nasogastric tubes1 is limited by poor quality studieswhich comprise case studies, small prospective studies, retrospectivestudies and no randomised clinical trials. Their suggested method tomeasure tube position is checking the pH of gastric aspirate1, but pHreadings are influenced by medication and enteral feed also it may bedifficult to aspirate from fine bore tubes2,3. This may lead to anincrease in the use of x-rays which are only accurate at one point intime, increase radiation exposure, are not cost effective4 and not alwayspractical/possible in patients’ homes or small hospitals.They recommend that injection of air down the tube and auscultationover the stomach, “the whoosh test” be abandoned on the basis of smallstudies and case reports3. Using "the whoosh test" alone has led to deathsfrom undetected tube displacement, although in terms of the total numberof tubes inserted the absolute risk of death from tube displacement isprobably small. However if two imperfect tests such as “the whoosh test”and pH measurement are used in combination it seems obvious that theoverall accuracy will increase. Basing clinical practice on imperfect advice is not ideal, however webelieve that “the whoosh test” could be made more reliable with theintroduction of a proper protocol and staff training. Training isessential although difficult without adequate research. Perhaps the NPSAare not going far enough in funding a systematic review. We believe thatprospective studies which test the sensitivity and specificity of themethods for confirming tube position against a gold standard such as tubeinsertion under x-ray guidance are urgently required.