A nasogastric tube (NG tube) is a thin, flexible plastic tube inserted through the nasal passage, down the throat and esophagus, until its tip rests temporarily within the stomach. This non-surgical medical device provides a direct conduit to the stomach for various therapeutic and diagnostic purposes. This method offers a relatively quick way to manage medical conditions that prevent normal oral intake or require direct stomach access.
Anatomy and Function of the NG Tube
NG tubes are constructed from materials like polyurethane, silicone, or polyvinyl chloride (PVC). They are sized using the French (Fr) gauge system, where smaller numbers indicate a narrower diameter. Fine-bore tubes (6 Fr to 12 Fr) are typically used for feeding, while larger-bore tubes (14 Fr to 18 Fr) are reserved for gastric drainage or aspiration.
The tube’s design varies based on its function. A Levin tube is a single-lumen design used for medication or short-term feeding. The Salem Sump tube features a double lumen; the smaller second channel acts as a vent to prevent the suction channel from adhering to the stomach lining during continuous drainage. The tube transports substances, either delivering liquid nutrition and medication or removing gas and fluids from the stomach.
Medical Reasons for Use
The applications for NG tube placement center on managing the gastrointestinal tract when the natural oral route is compromised. A primary use is enteral feeding, which provides nutritional support directly to the stomach for patients unable to swallow safely (dysphagia) or those who are unconscious. This method ensures individuals who cannot meet their caloric needs orally still receive necessary nutrients and hydration. Fine-bore tubes are preferred for this purpose to enhance patient comfort.
Gastric Decompression
Gastric decompression involves removing accumulated air, fluid, or other contents from the stomach using suction. This is frequently necessary in cases of bowel obstruction, paralytic ileus, or after certain surgeries where the digestive system is temporarily dysfunctional. Decompression relieves painful pressure and distention, preventing nausea, vomiting, and aspiration of stomach contents into the lungs.
Medication and Diagnostics
The tube is also used to administer medications when a patient cannot take them by mouth. In acute situations, NG tubes serve diagnostic purposes, such as aspirating stomach contents to check for signs of bleeding or to analyze the gastric pH level. They can also be used in emergencies to remove ingested toxins or poisons from the stomach.
The Insertion Process
NG tube placement is typically performed at the bedside, beginning with careful measurement of the required length. The standard method measures the tube from the tip of the nose to the earlobe, and then down to the xiphoid process. The tip of the tube is coated with a water-soluble lubricant to ease its passage through the nasal cavity.
The tube is gently guided through the chosen nostril toward the back of the throat and down the esophagus. To facilitate movement, the patient is often asked to tuck their chin and swallow small sips of water. Swallowing helps close the entrance to the trachea, reducing the risk of the tube accidentally entering the lungs. If the patient experiences coughing, choking, or respiratory distress, the tube must be withdrawn immediately.
Confirmation of the tube’s final position is critical before any substance is administered. An improperly placed tube poses a serious aspiration risk. While preliminary checks like aspirating fluid are sometimes used, the most reliable method for confirming placement is an X-ray. Alternatively, testing the pH of the aspirated fluid can confirm gastric placement, as stomach contents are highly acidic, typically a pH of 4 or below.
Daily Care and Management
Proper daily care maintains the NG tube’s function and minimizes patient discomfort. The tube must be securely fastened to the nose or cheek with tape or a specialized securing device to prevent accidental dislodgement. The tape should be changed daily and alternated between sites to prevent constant pressure and skin breakdown.
Patients often experience side effects, including a sore throat, nasal irritation, and dry mouth, due to reduced oral intake. Regular oral care, such as brushing teeth and using mouthwash, is important for hygiene and comfort. To ensure the tube remains functional, it must be flushed with water before and after each feeding or medication administration.
Monitoring the tube’s external length is an ongoing way to check for migration or dislodgement, which requires immediate re-verification of placement. Medical staff must be notified promptly if the patient develops signs of complication, including:
- Severe pain.
- Persistent coughing.
- Difficulty breathing.
- The tube appears blocked or damaged.
These signs may indicate a serious complication, such as the tube moving out of the stomach or into the lungs.