Nasogastric tube depth: the 'NEX' guideline is incorrect

Misplacing 17-23% of nasogastric (NG) tubes above the stomach ( Rollins et al, 2012 ; Rayner, 2013 ) represents a serious risk in terms of aspiration, further invasive (tube) procedures, irradiation from failed X-ray confirmation, delay to feed and medication. One causal factor is that in the National Patient Safety Agency (NPSA) guidance to place a tube, length is measured from nose to ear to xiphisternum (NEX) ( NSPA, 2011 ); NEX is incorrect because it only approximates the nose to gastro-oesophageal junction (GOJ) distance and is therefore too short. To overcome this and because the xiphisternum is more difficult to locate, local policy is to measure in the opposite direction; xiphisternum to ear to nose (XEN), then add 10 cm. The authors determined whether external body measurements can be used to estimate the NG tube length to safely reach the gastric body. This involved testing the statistical association of body length, age, sex and XEN in consecutive critically ill patients against internal anatomical landmarks determined from an electromagnetic (EM) trace of the tube path. XEN averaged 50 cm in 71 critically ill patients aged 53±20 years. Tube marking and the EM trace were used to determine mean insertion distances at pre-gastro-oesophageal junction (GOJ) (48 cm), where the tube first turns left towards the stomach and becomes shallow on the trace; gastric body (62 cm), where the tube reaches the left-most part of the stomach; and gastric antrum (73 cm) at the midline on the EM trace. Using body length, age, sex and XEN in a linear regression model, only 25% of variability was predicted, showing that external measurements cannot reliably predict the length of tube required to reach the stomach. A tube length of XEN (or NEX) is too short to guarantee gastric placement and is unsafe. XEN+10 cm or more complex measurements will reach the gastric body (mid-stomach) in most patients, but because of wide variation, external measurements often fail to predict a safe distance. Only the EM trace or possibly direct vision can show in real time whether the tip has safely reached the gastric body.