A nasogastric tube (NG tube) is a flexible tube inserted through the nose into the stomach, used to deliver nutrition, medications, or remove stomach contents. Confirming its placement is the most important safety step, as the tube can easily be misplaced into the respiratory tract (lungs). Administering fluids or food into a misplaced tube can lead to severe complications like aspiration pneumonia, pneumothorax, and death. Verifying the tube’s correct location is mandatory to prevent these life-threatening events.
The Gold Standard for Initial Placement
Radiographic confirmation, specifically a chest X-ray, is the definitive method for verifying the initial placement of a newly inserted NG tube. This is considered the gold standard because it offers clear, visual confirmation of the tube’s entire path. The X-ray must include the chest and the upper abdomen to ensure the tube’s tip is correctly positioned.
A trained healthcare professional must trace the tube’s path to confirm it descends through the esophagus, not the bronchi or lung. The tip must be clearly visible below the diaphragm and ideally positioned in the body or antrum of the stomach. Specifically, the tip should be located at least 10 centimeters below the left hemi-diaphragm to ensure it has passed the gastroesophageal junction.
While the X-ray provides the most accurate confirmation, it is not practical for routine, repeated checks due to radiation exposure, cost, and potential delays in feeding or medication. Misinterpretation of the X-ray image remains a concern, requiring proper training in reading these images. Since X-ray confirmation can delay the start of treatment, reliable bedside methods are necessary for ongoing verification.
Essential Bedside Confirmation Methods
For routine, ongoing checks after initial X-ray confirmation, the most reliable bedside technique is pH testing of the aspirate. This method relies on the highly acidic environment of the stomach to confirm the tube’s location. Gastric fluid is naturally acidic, typically showing a pH value of 5.5 or lower.
To perform the check, a small amount of fluid is gently aspirated from the NG tube using a syringe. This fluid is then placed onto a specialized pH indicator strip. If the tube is correctly placed in the stomach, the paper should display a color corresponding to a pH of 5.5 or less.
Conversely, fluid aspirated from the respiratory tract (lungs) is almost always alkaline, typically showing a pH of 6 or higher. If the pH reading is 6 or greater, the tube’s position is considered unsafe, and a chest X-ray must be performed immediately to confirm its location. Certain anti-acid medications can temporarily raise the stomach’s pH, which may result in a false reading and necessitate a confirmatory X-ray.
Unreliable and outdated methods must be avoided for placement confirmation. The auscultatory or air bolus method, often called the “whoosh test,” involves injecting air into the tube while listening over the stomach with a stethoscope. This technique is unsafe and no longer recommended because a “whooshing” sound can be heard even if the tube is coiled in the esophagus or placed in the respiratory tract, creating a false sense of security. Similarly, visual assessment of the aspirate’s color is unreliable, as both respiratory and gastrointestinal fluids can appear similar.
Safety Protocols and Re-Checking Frequency
NG tube placement must be re-checked frequently to ensure patient safety, as tubes can easily become dislodged even after successful initial confirmation. The most important protocol is to check the tube’s position before every feeding or medication administration. This rule is absolute, regardless of how recently the tube was last checked.
Immediate re-confirmation is mandatory if there is any suspicion that the tube has moved. This includes situations where the patient has episodes of coughing, vomiting, or retching, or if they report new respiratory symptoms or discomfort. A primary step is to document and regularly check the external measurement of the tube at the nostril, ensuring the centimeter marking has not changed from its original confirmed position.
If the external length has changed, or if any pH test yields an unsafe result, the tube should not be used. In any case of doubt regarding the tube’s location, all administrations must stop immediately. The tube must be re-verified using a reliable method, which means either repeating the pH test or obtaining a confirmatory chest X-ray.