A nasogastric tube (NGT) is a flexible tube passed through the nose, down the esophagus, and into the stomach. Its primary purpose is to deliver nutrition, fluids, or medication, or to remove stomach contents for decompression. Accurate measurement of the required insertion length is essential for safe placement. Incorrect measurement risks misplacement into the trachea and lungs, which can lead to severe complications like fatal aspiration pneumonia. Precise measurement ensures the tube tip safely reaches the stomach while avoiding the respiratory tract.
The Standard Anatomical Measurement (NEX Method)
The most widely taught technique for estimating insertion length in adults is the Nose-Ear-Xiphoid (NEX) method. This measurement relies on three external anatomical landmarks to approximate the distance to the stomach. The process begins by placing the tip of the NGT at the patient’s chosen nostril.
From the nostril, the tube is extended straight back to the earlobe or the tragus, the small cartilage in front of the ear canal. The measurement then continues from the earlobe, following a straight line down the torso to the xiphoid process, the lower tip of the sternum.
Once the tube is positioned over all three points, that final distance is marked on the tube. This mark serves as the insertion guide, indicating the length that must be passed to ensure the tube tip reaches the stomach.
Passing the tube to the marked NEX length guides the tip past the lower esophageal sphincter and into the gastric cavity. This measurement is documented so staff can check if the tube has moved post-insertion by comparing the external length visible at the nostril to the original mark.
Adjusting Length Measurements for Specific Patients
While the NEX method provides a standard guideline, it can be insufficient or inaccurate in certain patient populations, often resulting in tubes that are too short. This limitation increases the risk of esophageal misplacement, where the tube tip rests in the esophagus instead of the stomach, especially in patients with altered anatomy or specific body types.
To enhance accuracy, specialized formulas have been developed. These include the Hanson formula, which incorporates the distance from the nose to the umbilicus, and the XEN+10 method (NEX plus 10 cm). Research suggests that simply adding an extra 10 centimeters to the NEX measurement may reduce the risk of the tube ending prematurely in the esophagus.
Pediatric patients require different measurement approaches due to their rapidly changing anatomy. For infants and children, methods such as the Nose-Ear-Mid-Umbilicus (NEMU) or age-related, height-based formulas are often preferred over NEX.
Patients with conditions like neck surgery, facial trauma, or previous gastrointestinal procedures also require modified techniques. These situations sometimes necessitate the use of electromagnetic guidance to determine the precise internal distance needed for safe placement.
Critical Verification of Tube Placement
Relying on calculated length alone is insufficient for patient safety; placement must be confirmed after every insertion. The most definitive method for confirming the tube is correctly positioned in the stomach and not the lungs is radiographic confirmation, specifically a chest X-ray.
The NGT contains a radiopaque line, making it visible on the image. This allows a clinician to confirm its path down the esophagus and the final location of the tip below the diaphragm in the stomach. If the tip is visible in the trachea or a bronchus, it indicates pulmonary insertion, and the tube must be immediately removed.
The X-ray is considered the gold standard because it provides direct, visual proof of the tube’s location. However, X-rays are not always practical for routine checks. A common bedside verification method involves aspirating fluid from the tube and testing its acidity.
Gastric fluid is highly acidic; a pH level of 5.5 or lower is considered a strong indicator that the tube is correctly positioned within the stomach. If the aspirate has a pH greater than 5.5, or if no aspirate can be obtained, the placement is considered unsafe. A chest X-ray is then required before any feeding or medication can be administered.