CoNEX as a new method to estimate the tip position of a nasogastric tube: A pilot study

Background: The NEX-method (nose-earlobe-xiphoid process) is widely used to predict internal nasogastric tube length in adults. A possible alternative is the Hanson formula: (NEX x 0.38696)+30.37cm. Recent research revealed that, when using one of both methods, the tip position was located too close or even not beyond the lower esophageal sphincter (=LES) in > 20% of all patients. Assessment of the internal tube length by 3 radiologists in 183 patients suggested a correction of the Hanson formula: (NEX x 0.38696)+30.37cm+6cm. Aim of this current study was to determine whether this correction can be a valuable alternative to the other methods.Methods: A 3-month pilot study was conducted in a Belgian general hospital. External measurement to define the internal tube length was performed by 2 nutrition support nurses. The CoNEX method used to determine the internal tube length was (NEX x 0,38696)+36,37cm. After (re)positioning, 58 tubes were eligible to be assessed through X-ray by 2 independent radiologists. A correct tube position was defined as a tube placed with the tip 3 cm or more under the LES.Results: There is a significant difference between the use of the CoNEX method and the two other described methods to become an ideal tip position. The use of the CoNEX method (N=58) led to 100% of correctly positioned nasogastric tubes in all patients. It also resulted in a significantly higher probability to aspirate gastric contents after insertion of the tube: 69% of all patients vs. ≤56% in both two other methods.Discussion and Conclusion: The CoNEX method can be a valuable alternative to predict the internal tube position of a nasogastric tube but needs further research because of the small study population. It also makes it possible to obtain gastric aspirate in a higher amount of cases than the other two described methods.