Anatomy

The nasal cavity is lined by highly vascularized and innervated mucosa and continues posteriorly as the nasopharynx. Within the nasal cavity are the superior, inferior, and middle nasal conchae (turbinates), which divide the cavity into four passages (Fig. 203-3), the meatuses. Traditionally, the nasogastric tube is inserted blindly through middle and inferior meatuses. Beyond the nasal cavity, the pharynx extends from the base of the skull to the inferior border of the cricoid cartilage. It is divided into three parts: the nasopharynx, oropharynx, and laryngopharynx (hypopharynx). The nasopharynx gives rise to the oropharynx at the level of the soft palate, which then gives rise to the laryngopharynx (hypopharynx) at the superior border of the epiglottis (see Chapter 77, Nasolaryngoscopy, Fig. 77-6). The laryngopharynx becomes continuous with the esophagus at the inferior border of the cricoid cartilage. The posterior part of the upper nasopharynx is surrounded by the cribriform plate and the body of the ethmoid and sphenoid bones, which can easily be broken by a traumatic blow to the midface, resulting in a maxillofacial or basilar skull fracture. Such fractures can create a route into the cranial vault, which is a prerequisite for one of the most disastrous complications of inserting a nasogastric tube, intracranial intubation. This can result in brain damage or death. Therefore, placement of a nasogastric or nasoenteric tube in a patient with a possible skull or maxillofacial fracture should be avoided, if possible (an orogastric route may be a better option).

Figure 203-3 Pharyngeal anatomy: sagittal section of the head and neck.

(From Thibodeau C, Patton KT: Structure and Function of the Body, 11th ed. St. Louis, Mosby, 2000.)

Beyond the laryngopharynx and the larynx, the trachea lies anterior to the esophagus at the level of the cricoid bone and is supported by fibrocartilaginous tracheal rings. The superior aperture is covered by the epiglottis of the larynx during swallowing.

The anatomy also confers the ability to estimate the length of tube that should be inserted. Because the median distance from the anterior aspect of the nasal septum to the cricopharyngeus muscle (tracheoesophageal junction) is about 8 inches, and the esophagus is on average about 10 inches long, and given that the tip of a nasogastric tube should lie 4 inches below the gastroesophageal junction when in place, the nasogastric tube should ideally be secured at the 20- to 24-inch mark at the nasal vestibule. Alternatively, the distance can be approximated by holding the tube up to the patient’s ear and across to the nose, and then extending it to 6 inches below the xiphoid process (8 to 10 inches for a nasoenteric tube; this is described later in the Technique section).

The anatomy of children regarding the insertion of a nasogastric tube warrants a special note. Children have larger tonsils and adenoids, and their tongues are large compared to adults and may push into the oropharynx, all of which can hamper the insertion of a tube. At the same time, these tissues are soft and easily injured, thereby increasing the risk of bleeding with nasogastric intubation. Limiting the size of the tube to the smaller sizes of the nostrils and nasal cavity in children usually minimizes the difficulty with insertion, despite these anatomic differences.

Indications

Contraindications

All the following contraindications are relative.

Equipment and Supplies

TABLE 203-1 Enteral Alimentation Tubes

Preprocedure Patient Preparation

Although the insertion of a nasogastric tube is a common and fairly simple procedure, serious complications can occur. The risk for complications can be minimized by taking a few precautions: obtaining the full cooperation of the patient, informing the patient carefully at each step of the process, using a decongestant and local anesthesia for the nasal and retropharyngeal mucosa, premeasuring and marking the length of the tube needed for insertion, using gentle technique during insertion, and carefully confirming that the tube is in the proper position before use.

Insertion of a nasogastric tube is considered by many patients to be one of the most uncomfortable and distressful procedures they have ever experienced. Although most hospitals do not require written informed consent, the risks, benefits, indications, and any possible alternatives should be explained to patients. Even with the use of decongestants and anesthetics, patients should be prepared for some discomfort. The unpleasant nature of the procedure should not be minimized.

Patients should know that their eyes may water and they may have some tearing. They may have an intense tickling sensation or an urge to sneeze. During insertion, they may experience a gagging sensation. Swallowing rapidly will minimize this response and shorten the total length of the procedure. At some point during the procedure, they will probably be asked to assist by sniffing or later by swallowing. To help them swallow, give them a glass of water and a straw. If they are not able to swallow, if they will mimic swallowing or make the sound “eeee” it may help. Patients should be reassured that after the tube has been placed, they will usually adapt to it very soon and no longer notice it.

Before nasogastric tube removal, the patient should be informed of the procedure and what to expect. Towels, surgical Chux, or other drapes should be placed around the patient’s neck and chest. He or she should be handed an emesis basin and tissues.