The accuracy of methods for determining the internal length of a nasogastric tube in adult patients: a systematic review

Background Blind insertion of nasogastric (NG) tubes is performed for several reasons: nutrition and medication administration, gastric aspiration/decompression, and other, diagnostic reasons. Accidental intraesophageal and intestinal placement is common, and increases the risk of serious complications. Therefore, accurate determination of the internal length of the NG tube before placement is considered a prerequisite for achieving correct gastric positioning. Objectives We aimed to identify, assess, and summarize the evidence on the accuracy of methods for determining the internal length of an NG tube in adults. Methods Cochrane Library, Excerpta Medica database (EMBASE), PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), and Web of Science were searched up to 31 January, 2022. Studies were eligible when reporting data on the accuracy of methods for determining internal NG tube length in adults. Study selection, risk-of-bias assessment, and data extraction were performed independently by 2 investigators. Risk-of-bias was assessed using the Cochrane Risk-of-Bias Tool and the Joanna Briggs Institute Critical Appraisal Checklist for Cross Sectional Studies. A narrative synthesis of the results was then conducted. Results Twelve articles were included in this review. All studies were observational, cross-sectional in nature, except for 1 randomized controlled trial. Ten methods for determining the internal length of an NG tube were described. Correctly positioned NG tubes ranged from 13% to 99%. Results showed that the tip of the nose-earlobe-xiphoid distance (NEX) + 10 cm (mean: 59.9-60.7 cm) and (NEX x 0.38696) + 30.37 + 6 cm (mean: 56.6-56.7 cm) could potentially result in accuracy as high as 97.4% and 99.0%, respectively. Conclusions Current data do not provide conclusive evidence of 100% accuracy in finding a correctly placed NG tube when using a method for determining the internal length. Blind placement, using any of the documented methods, cannot be considered safe without additional verification of tube tip positioning. Furthermore, using any of these 10 methods does not reduce the risk of pulmonary intubation.