An Orogastric (OG) tube is a flexible device inserted through the mouth and guided down the esophagus until its tip rests within the stomach. This procedure is a fundamental intervention in the management of critically ill patients, particularly those who require mechanical ventilation. The primary function of an OG tube is to provide direct access to the stomach for gastric decompression (removal of air and fluid) or for the administration of liquid nutrition and medications. Inserting an OG tube into a patient who is already intubated presents a specific procedural challenge because the Endotracheal Tube (ETT) occupies a significant portion of the oropharynx. This article focuses on the rationale, preparation, and technique required for the successful placement of an OG tube in a patient with an ETT already in place.
Why OG Tubes Are Necessary for Intubated Patients
The necessity for an OG tube in a mechanically ventilated patient stems from several physiologic and mechanical factors related to critical illness and airway management. Intubation impairs the normal protective airway reflexes, significantly increasing the risk of pulmonary aspiration. Gastric decompression is therefore employed to reduce the volume of stomach contents that could be regurgitated and then aspirated into the lungs.
Mechanical ventilation itself can contribute to gastric distension, especially if bag-mask ventilation was used before intubation, as air may be inadvertently forced into the stomach. This gastric inflation can elevate the diaphragm, which compromises lung capacity and interferes with effective breathing mechanics. Placing an OG tube allows for the removal of this trapped air, optimizing the patient’s ventilation and lung compliance.
Critically ill patients often require nutritional support and medications that cannot be taken orally due to their underlying condition or level of consciousness. The OG tube provides a reliable route for delivering enteral feeding, which is the preferred method of nutrition over intravenous feeding in many intensive care settings. Using the oral approach (OG tube) over the nasal approach (NG tube) is often preferred in intubated patients to avoid complications like sinusitis or nasal bleeding.
Essential Preparations Before Insertion
Successful OG tube insertion relies heavily on preparation, beginning with the assembly of the necessary equipment. Tube selection depends on purpose; a larger bore (typically 14 to 18 French for adults) is used for decompression, while a smaller bore is used for long-term feeding. Required supplies include a large syringe (often 60 milliliters) for aspiration, water-soluble lubricant, securing tape, and a stethoscope.
Proper patient positioning involves ensuring the patient is lying supine with the head of the bed slightly elevated, if tolerated, to aid in the tube’s descent and prevent reflux. Determining the correct insertion length is crucial to ensure the tip reaches the stomach. This is achieved by measuring the distance from the patient’s mouth to the earlobe and then down to the xiphoid process (the small cartilaginous section at the lower end of the sternum).
This traditional measurement, called the O-E-X (mouth-earlobe-xiphoid) method, is marked on the tube. This marked length is the minimum distance the tube must be advanced to ensure gastric placement and prevent coiling in the esophagus. The tip of the tube is then generously coated with the water-soluble lubricant to minimize friction and tissue trauma during passage.
Step-by-Step Guide to Insertion Technique
The actual insertion of the OG tube in an intubated patient leverages the presence of the ETT. After lubricating the tube, the operator should gently guide the tip into the patient’s mouth, aiming it toward the back of the throat. The ETT acts as a barrier, blocking the tube from accidentally entering the airway.
The OG tube should be advanced along the side of the ETT, toward the posterior pharyngeal wall, directing it into the esophagus. The operator may use a finger to physically guide the tube around the curve of the oropharynx and past the glottic opening. Maintaining a gentle, steady force is necessary, as excessive force can cause trauma or cause the tube to coil.
The tube is advanced in a smooth, continuous motion until the pre-measured mark reaches the patient’s mouth. If resistance is encountered, slight rotation or a small withdrawal and re-advance may help it pass. Since the patient is sedated, typical signs of misplacement, such as coughing or gagging, are absent, but sudden changes in ventilator pressures may indicate a problem.
If difficulty is encountered, techniques such as elevating the patient’s jaw or using a rigid guide (like a stylet placed inside the OG tube) can be employed to stiffen the tube. Some advanced techniques involve using a laryngoscope to directly view the hypopharynx and guide the tube past the vocal cords. Once the predetermined insertion length has been reached, the final step of confirming position is performed.
Verifying Correct Tube Placement and Securing
Before the OG tube is used, its placement must be definitively confirmed to prevent the catastrophic complication of administering fluids into the lungs. The gold standard for confirming intragastric placement is a chest and abdominal X-ray, which visually demonstrates the tube’s radio-opaque line extending below the diaphragm and coiling within the stomach. This radiological confirmation is mandatory, particularly before initiating any feeding regimen.
Several bedside methods are used as initial checks, but they are not reliable enough on their own to replace X-ray verification for feeding tubes. One common method is to aspirate contents from the tube and test the fluid’s pH. Gastric fluid is highly acidic, and a pH reading of 5.5 or lower strongly suggests the tube is correctly positioned.
Another method involves injecting a small volume of air (typically 10 to 30 milliliters) through the tube while listening with a stethoscope over the epigastrium. The sound of a distinct rush or “gurgle” suggests the tube has entered the stomach, but this technique cannot reliably distinguish between the stomach and the lung, limiting its use. Once placement is confirmed, the tube is secured to the patient’s cheek or face using a specialized tube holder or medical tape to prevent dislodgement.