J Korean Soc Emerg Med.  2021 Apr;32(2):143-150.

The effectiveness of the capnographic unit and ultrasonography for confirmation of nasogastric tube location at the emergency room

• Bang HJ
• Kim HM
• So BH
• Jeong WJ

Abstract

Objective
This study was designed to verify the effectiveness of capnography and ultrasound for confirmation of the location of the nasogastric tube (NGT) in the emergency room (ER).
Methods
In this prospective single-blinded study, carried out on 137 patients over 19 years of age, the NGT location was confirmed by capnography in 63 patients and by ultrasound in 74 patients. The capnography and ultrasound scans were performed in random order, while auscultation was performed and chest X-rays were taken for all patients. Capnography was performed by checking the end-tidal carbon dioxide (ETCO₂) level and the wave form after inserting the NGT. An ultrasound scan was conducted on the neck, gastroesophageal junction and stomach. The X-ray results were interpreted by a doctor who had not inserted the NGT.
Results
The sensitivity and specificity of auscultation were 98.43% and 10%, respectively. After 30 cm of NGT was inserted ETCO₂ was measured through the capnography, and was found to be ranging from 0-23. When the capnography showed an ETCO₂ value of less than 4, the tube was considered to be inserted in the stomach. In such a case, the specificity was 100%, but the sensitivity was only 46.43%. The sensitivity and specificity of the ultrasound were 92.96% and 66.67%, respectively. In addition, the positive predictive value was confirmed to be 100% and 98.51% when using capnography and ultrasound, respectively.
Conclusion
When the NGT is inserted in the ER, it is possible to use ultrasound and capnography for confirmation of its location. However, in some patients, when neither method can confirm the location, a chest X-ray will still be needed.

Keyword

Nasogastric tube; Auscultation; Capnography; Ultrasonography