A nasogastric tube (NG tube) is a slender, flexible plastic tube temporarily inserted through the nose, down the throat and esophagus, and into the stomach. This medical device delivers nutrition and medications to patients who cannot safely swallow. It is also used for gastric decompression, which involves suctioning out stomach contents to relieve pressure from conditions like bowel obstructions. Correct positioning is essential for the tube’s safe function. Healthcare providers must confirm the tube’s location before its initial use and routinely check it, as administering substances into a misplaced tube can have severe consequences.
The Ideal Resting Spot
The primary goal for NG tube placement is for the tip to rest comfortably within the main body of the stomach, specifically the fundus and corpus. A correctly positioned tube is visible on imaging just below the left side of the diaphragm.
To maintain efficacy and prevent complications, the tip should extend a minimum of 10 centimeters past the gastroesophageal junction (the muscular opening between the esophagus and the stomach). This depth helps anchor the tube and reduces the chance of it moving backward, which could cause irritation or reflux. The tube should not be coiled in the esophagus or throat, nor should it pass through the pylorus into the small intestine, unless a post-pyloric tube was intended.
Checking for Correct Placement
Verifying the NG tube’s location is the most important safety step. The gold standard for confirming placement is a chest and abdominal X-ray, which provides a clear visual of the tube’s entire path. The X-ray confirms the tube has bypassed the airways and rests safely in the gastric cavity.
A secondary, reliable method used at the bedside is testing the pH of fluid aspirated from the tube. Gastric fluid is highly acidic due to hydrochloric acid, typically having a pH value between 1.0 and 5.5. This low pH contrasts sharply with fluid found in the respiratory tract, which is generally more alkaline (pH greater than 6.0).
Visual inspection of the aspirated fluid can also provide a clue; gastric aspirate often appears grassy green, brown, or colorless. However, color alone is not a definitive indicator and must always be paired with pH testing or X-ray confirmation. The outdated method of auscultation (injecting air and listening for a rush over the stomach) is no longer recommended because a similar sound can be heard even if the tube is misplaced in the lungs.
Risks of Tube Misplacement
The most serious risk associated with an NG tube is pulmonary misplacement, where the tube inadvertently enters the trachea and bronchial tree instead of the esophagus. This misplacement carries life-threatening consequences. If feeding or medication is delivered into a tube resting in the lungs, it can cause aspiration pneumonia, a severe lung infection.
In some cases, a misplaced tube can puncture the lung lining, leading to a pneumothorax (collapsed lung). Even if the tube avoids the lungs, it may coil up in the esophagus or throat, preventing successful delivery or decompression. Misplaced tubes can also cause mild complications like chronic irritation of the nasal passages or the esophagus.
The risk of these complications underscores why robust verification procedures, such as X-ray imaging and pH testing, are crucial before any substance is administered through the tube.