Nasogastric Intubation Technique - Medscape Reference

Explain the procedure of nasogastric (NG) intubation, as well as its benefits, risks, complications, and alternatives, to the patient or the patient's representative.

Examine the patient's nostril for septal deviation. To determine which nostril is more patent, ask the patient to occlude each nostril and breathe through the other.

Instill 10 mL of viscous lidocaine 2% (for oral use) down the more patent nostril with the head tilted backward (see the images below), and ask the patient to sniff and swallow to anesthetize the nasal and oropharyngeal mucosa. In pediatric patients, do not exceed 4 mg/kg of lidocaine. Wait 5-10 minutes to ensure adequate anesthetic effect.

Aspiration of viscous lidocaine into a syringe. View Media Gallery Instillation of viscous lidocaine 2%. View Media Gallery

A commonly used approach to estimating the length of insertion has been to measure the distance from the tip of the nose, around the ear, and down to just below the left costal margin. This point can be marked with a piece of tape on the tube. When the Salem Sump (Kendall, Mansfield, MA) NG tube (NGT) is used in adults, the estimated length usually falls between the second and third preprinted black lines on the tube (see the image below).

Estimation of nasogastric tube length from nostril to stomach. View Media Gallery

Apart from the nose-to-ear-to-xiphisternum (NEX) method, several other methods for determining the length of the tube have been described. Among the various options, a formula based on gender, weight, and nose-to-umbilicus measurement while lying flat was found to be safer and more accurate in a study by Santos et al. [13]

A review by Boeykens et al argued that the NEX method should not be used for estimating insertion length, because of the risk of underestimation, which could lead to esophageal intubation and aspiration. [14] The authors described a corrected NEX (coNEX) method that used a corrected Hanson formula: [(NEX × 0.38696) + 30.37 + 6 cm]. This method yielded a correct tip position (> 3 cm in the stomach) in all patients, with 94% at 6 cm or more under the left hemidiaphragm and no tubes seen to be migrating back into the esophagus.

Position the patient sitting upright with the neck partially flexed. Ask the patient to hold the cup of water in his or her hand, and put the straw in his or her mouth. Lubricate the distal tip of the NGT (see the image below).

Nasogastric tube lubrication with water-based lubricant. View Media Gallery

Gently insert the NGT along the floor of the nose, and advance it parallel to the nasal floor (ie, directly perpendicular to the patient's head, not angled up into the nose) until it reaches the back of the nasopharynx, where resistance will be met (10-20 cm). At this time, ask the patient to sip on the water through the straw and start to swallow (see the image below). Continue to advance the tube until the distance of the previously estimated length is reached (see the video below).

Patient flexing his neck and drinking water while a nasogastric tube is inserted. View Media Gallery Nasogastric tube insertion. View Media Gallery

If, at any time, the patient experiences respiratory distress, is unable to speak, or has significant nasal hemorrhage, or if the NGT meets significant resistance, stop advancing the tube and withdraw it completely.

Fan et al described a no-swallow technique of NG intubation that relieved patient discomfort during the procedure. [15] In this technique, when the NGT reached the pharynx, patients were required to take a deep breath and hold it, instead of swallowing as in the conventional technique. During breath-holding, the epiglottis covers the throat and the glottis closes, thereby reducing the likelihood of the tube entering the trachea. When the NGT was inserted 15-20 cm, the patient was required to perform abdominal breathing to reduce discomfort and avoid failure of intubation (some patients can only hold their breath for a short time).

This no-swallow technique was found to yield an increase in the success rate at first intubation, as well as reductions in the occurrence of nausea, tearing, mucosal injury, and changes in vital signs (heart rate, breath, systolic pressure), when compared with the technique used in the control group. [15]

A common practice has been to verify proper placement of the NGT by auscultating a rush of air over the stomach using the 60 mL Toomey syringe (see the image below) or by aspirating gastric content. The widespread use of the air insufflation method notwithstanding, various authors regard it as unsafe and inadvisable. [14]

Auscultation over the stomach. View Media Gallery

The authors recommend always obtaining a chest radiograph (see the image below) in order to verify correct placement, especially if the NGT is to be used for medication or food administration. Colorimetric capnography is another valid method for verifying NGT positioning in mechanically ventilated patients. [16]

Nasogastric tube in lung. View Media Gallery

In a retrospective descriptive analysis (N = 215) aimed at identifying factors associated with insufficient NGT visibility on radiography, Torsy et al reported that in 14.9% of patients, the image quality was insufficient to determine the position of the tube. [17] The factors associated with poor visibility were high body mass index (BMI), male sex, and the absence of a guide wire inside the NGT at the time of chest radiography.

Although radiographic confirmation of NGT position is conventionally considered the gold standard, it exposes the patients to ionizing radiation. In addition, radiologic investigations can be misinterpreted and may be associated with feeding delay and significant costs. Methods such as ultrasonography (US), electromagnetic guidance, and camera technology could detect respiratory placement earlier, reduce exposure to ionizing radiation, and shorten the time to NGT feeding.

Choi et al reported the use of US to confirm the placement of NGTs in pediatric patients. [18] They found that this method yielded good esophageal imaging; however, the gastric imaging was challenging, and it was improved by injecting an air bolus.

Despite efforts by national organizations, NGT placement still is not a fail-safe process. A scoping review by Hamdaoui et al examined clinical practices and national guideline adherence in the United Kingdom with respect to placement and position confirmation of NG feeding tubes in adults. [19] Substantial variations were noted. The review focused on the following three specific themes:

• Referral and authorization of radiography - Different practices are in place for checking NGT position and ordering a chest radiograph; some local policies also require that the referral mention the length of the NGT at the nostril and the pH of the gastric aspirate
• Examination description - An NGT check is not always clearly differentiated from a standard chest radiograph
• Visualization of NGT tip - There is little agreement in guidelines or the literature about where the NGT tip should be placed

Manometry is another safe and reliable method for differentiating airway placement of an NGT from gastric placement. [20] A biphasic pressure change synchronous with airway pressure during mechanical ventilation indicates airway misplacement, and a pressure change during compression of the epigastric area indicates a gastric placement.

Apply benzoin or another skin preparation solution to the nose bridge. Tape the NGT to the nose to secure it in place (see the image below). If clinically indicated, attach the tube to wall suction after verification of correct placement.

Secured nasogastric tube. View Media Gallery

Pearls

A randomized controlled trial by Tongyoo et al found that the use of lidocaine nasal drops before NGT insertion reduced discomfort and lowered the rate of procedure-related complications. [21] Patients received two or three drops of either 3% lidocaine or normal saline, and the NGT was lubricated with jelly in all cases. After insertion, pain (assessed via Visual Analogue Scale [VAS]) was signifcantly lower in the lidocaine group (1.41 ± 0.50) than in the placebo group (4.54 ± 1.03); procedural time was shorter in the lidocaine group as well (1.52 ± 0.76 vs 3.38 ± 1.36 min). Complications (eg, vomiting, coughing, difficulty breathing, and aspiration) occurred only in the placebo group.

During insertion, if concern exists that the NG tube is in the incorrect place, ask the patient to speak. If the patient is able to speak, then the tube has not passed through the vocal cords and/or lungs.

The NG tube may coil in the nasopharynx or oropharynx. If this occurs, or if the tube is difficult to pass in general, try curling the distal end and partially freezing it in a cup of ice so it temporarily holds its curled shape better. Insert the lubricated tube tip through the nose with the curled end pointing downward. Once the distal tip passes into the hypopharynx, the curved tip faces anteriorly. Rotate the tube 180º so that the curved end points posteriorly toward the esophagus. Continue to insert in the usual manner by having the patient swallow water.

Another option (applicable only in patients who are sedated and paralyzed) is to place two or three fingers through the patient’s mouth into the oropharynx. The fingers are used to guide the NG tube into the hypopharynx.

Lifting the thyroid cartilage anterior and upward might open the esophagus and allow passage into the proximal esophagus.

A method of freezing an NG tube with distilled water was shown to increase the success rate of insertion for intubated patients. [22]

Direct laryngoscopy or video laryngoscopy can aid in placing an NG tube in sedated patients by enabling visualization of the tip entering the esophagus. [23]

A randomized crossover manikin trial conducted by Li et al introduced a newer technique of gastric tube placement via an 8.4-French deflection flexible ureteroscope, which served as a visual guidance system. [24] Placement time was substantially shorter and the incidence of procedure-related complications considerably lower than with the standard method.

In a study by Lee et al that used a manikin simulator, the time required for NG tube placement was reduced significantly in both intubated and nonintubated patients if the procedure was done under visualization with a video-guided laryngoscope, as compared with manual and laryngoscope-assisted intubation. [25]

Endotracheal tube assistance and video laryngoscopy can be used to facilitate NG tube insertion in anesthetized and intubated patients. The success rate is increased, and complications such as kinking of the tube are reduced. [26]

Although pH, enzyme, bilirubin, and carbon dioxide testing have been used to distinguish respiratory from gastrointestinal placement of NG tubes, none of these methods has enabled detection of tube placement in the esophagus or gastroesophageal junction. [27] Therefore, the authors recommend the routine use of x-ray verification.

A survey of critical care nurses around the United States showed that recommendations from multiple national-level organizations to obtain radiographic confirmation that each blindly inserted feeding tube is correctly positioned before the first use of the tube are not adequately implemented. [28] Auscultation is widely used despite recommendations to the contrary.

In a randomized, controlled study that included 200 anesthetized patients, Appukutty et al found that three techniques can increase the success rate of NG tube placement. [29] The use of a ureteral guide wire as stylet or a slit endotracheal tube as an introducer increased the success rate in comparison with control subjects, though the latter technique significantly lengthened the time for insertion. However, head flexion with lateral neck pressure proved to be the easiest technique, with a high success rate and the lowest complication rate.

Sharma et al described the use of a bubble technique for NG tube insertion, which they found to have higher confirmation rate than the conventional technique (76.8% vs 59.7%). [30] In this technique, 2% lidocaine jelly was added to the proximal end to form a single bubble, and tube placement was later confirmed by means of fluoroscopy.