How to Measure an NG Tube for Proper Placement

The most widely taught method for measuring a nasogastric (NG) tube before insertion, known as the NEX technique, consistently underestimates the length needed to reach the stomach. Research has shown that NEX predicts a tube length of roughly 51 cm in adults, while the actual distance to the body of the stomach is closer to 61 cm, meaning the tube tip may never clear the lower esophagus in a significant number of patients.¹ That gap has real consequences, and understanding how to measure correctly, which alternative methods exist, and how to confirm placement afterward can prevent serious complications.

What the NEX Method Actually Measures

NEX stands for nose-to-ear-to-xiphoid process. You hold the tip of the tube at the patient’s nose, loop it to the earlobe, then extend it down to the xiphoid process at the bottom of the sternum. The measured distance becomes the insertion depth. It has been the standard taught in nursing and medical programs for decades, and many hospital protocols still list it as the primary measurement technique.

The problem is straightforward: the NEX distance roughly approximates the path from the nose to the gastroesophageal junction, the point where the esophagus meets the stomach. It does not account for the additional length needed to get the tube tip safely past that junction and into the body of the stomach.² A tube sitting right at the gastroesophageal junction is technically in neither the esophagus nor the stomach in a functionally useful way. Feed or medication delivered there can reflux upward into the esophagus and potentially into the lungs.

A study comparing several measurement methods in adults found that NEX predicted a median length of about 51 cm while the actual distance to the gastric body flexure was 61 cm. The potential risk for esophageal placement using NEX was over 96%, and about 15% of patients faced a definite risk of the tube ending up in the esophagus rather than the stomach.¹ Those numbers make NEX one of the least reliable options for adult patients, despite being the most commonly used.

Measurement Methods That Perform Better

Several alternatives to NEX have been studied, though none is universally adopted yet. The most promising option in the adult research is a modification sometimes called XEN+10 or NEX+10, which simply adds 10 cm to the standard NEX measurement. In the same study that found NEX predicted 51 cm, XEN+10 predicted a median of 61 cm, matching the actual distance to the gastric body flexure. The definite risk of esophageal placement dropped to 0% with this method, though about 43% of patients still had a potential (not definite) risk of the tube sitting too high.¹

Other approaches try to move away from external landmarks altogether and use height-based formulas, since a person’s height correlates reasonably well with their internal anatomy. The Hanson formulas, for example, use height to calculate predicted insertion depth. One version (Hanson_A) predicted about 50.5 cm and another (Hanson_B) predicted about 56.1 cm, both falling short of the 61 cm target, though Hanson_B cut the definite esophageal risk down to around 1%. A narrative review in Critical Care concluded that the most frequently used insertion-length technique is too short and that safer methods are needed, along with more robust evidence to settle on a single best practice.³

A randomized trial comparing two estimation methods found that in more than 20% of all patients, both methods underestimated the required tube length.⁴ The consistent takeaway across these studies is that no single external measurement perfectly predicts internal anatomy for every patient, and erring on the side of slightly longer rather than shorter is generally safer, provided you verify placement afterward.

Measuring in Children and Newborns

Pediatric patients present an entirely different measurement challenge because of the dramatic range in body size from a premature newborn to a teenager. NEX performs even worse in children relative to alternatives specifically designed for younger populations.

Two methods outperform NEX in children: NEMU (nose-to-ear-to-midpoint-between-umbilicus-and-xiphoid) and ARHB (age-related height-based). In a study of children aged one month to 17 years, about 97% of tubes measured with NEMU and 89% measured with ARHB landed in the correct position, compared to only 59% with NEX. When researchers calculated the odds, using NEX instead of NEMU made misplacement roughly 23 times more likely.⁵ In neonates, a similar pattern held: NEX instead of NEMU raised misplacement odds nearly eightfold.⁶

For the smallest newborns, weight-based formulas have been developed because external landmarks on tiny bodies are difficult to use reliably. One widely referenced formula for nasogastric tubes in newborns is: insertion length in centimeters equals three times weight in kilograms plus 13. For orogastric tubes (inserted through the mouth), the formula uses plus 12 instead. In validation testing, this formula correctly flagged 100% of misplaced nasogastric tubes.⁷ For extremely low birth-weight infants under one kilogram, a different formula has been proposed: five times weight in kilograms plus 10.⁸ The existence of multiple competing formulas reflects how much internal anatomy varies even among newborns of similar size. No single formula covers every clinical scenario perfectly.

What Can Go Wrong With a Misplaced Tube

The risks of a tube that ends up in the wrong place range from uncomfortable to fatal. The most feared complication is pulmonary placement, where the tube passes through the larynx and into the airway instead of the esophagus. A retrospective analysis of over 500 radiographs taken to check tube position found that about 2.2% of NG tubes had been inadvertently placed in the airway and another 1% were coiled in the upper esophagus.⁹ If feed or medication gets delivered into the lungs, the consequences can include pneumonia, pneumothorax, and lung laceration.¹⁰

Even when the tube is in the general area of the esophagus or stomach, problems can arise. A tube sitting in the esophagus rather than the stomach can impair the lower esophageal sphincter, increasing the risk of gastric reflux, esophagitis, and aspiration. With prolonged use, a poorly positioned tube can cause nasal tissue damage, chronic stomach irritation, and gastrointestinal bleeding.¹¹ These risks underscore why both accurate measurement before insertion and verification afterward are critical.

Confirming the Tube Is in the Right Place

Measuring correctly is only half the process. Once the tube is inserted to the intended depth, you need to confirm it actually landed in the stomach. The traditional gold standard is a chest and abdominal X-ray, which shows the tube’s path and tip position. However, X-ray verification has its own limitations: it is a snapshot of one moment in time, and by the time the film is taken and read, the tube has already been placed. One analysis noted that X-ray is essentially “too late” to prevent the roughly 1.5% of blind tube placements that enter the lung, and it causes delays to feeding and medication administration.¹² Despite these drawbacks, X-ray remains the most widely accepted confirmation method.¹³

A bedside alternative is pH testing of aspirated fluid. If you can draw back fluid through the tube and its pH is 5.5 or below, it is likely gastric acid, which confirms stomach placement. This avoids the radiation exposure and delay of X-ray. The catch is that aspirate is not always obtainable. Research on a pH testing protocol found that it could be successfully applied in only about 42% of all placements, meaning the majority of patients still needed another verification method.¹⁴ Patients on acid-suppressing medications like proton pump inhibitors can also produce misleadingly high pH readings, making this test unreliable in that population.

One method that should not be used is the auscultation or “whoosh” test, where air is injected through the tube while someone listens over the stomach with a stethoscope. The sound of air entering the stomach was long thought to confirm placement, but air injected into the lungs or esophagus can also transmit sounds that mimic gastric placement. Case reports have documented life-threatening complications in patients where auscultation falsely confirmed correct positioning.¹⁵ Most current clinical guidelines advise against relying on auscultation as a verification technique.

Point-of-Care Ultrasound as an Emerging Alternative

Ultrasound is gaining attention as a verification method that avoids radiation and can be performed at the bedside in real time. A pilot study in an intensive care unit tested two ultrasound approaches: directly visualizing the tube in the stomach, and an indirect technique called “dynamic fogging,” where a small amount of air or fluid is flushed through the tube while watching the stomach on ultrasound for the characteristic turbulence. Direct visualization confirmed placement in only about 30% of cases, but the dynamic fogging technique raised that to roughly 74–78%, with a specificity of 100%, meaning it never falsely confirmed a tube that was in the wrong place.¹⁶ The sensitivity is still not perfect, so a negative ultrasound finding does not rule out correct placement. But the high specificity means a positive finding is trustworthy, which can spare some patients from unnecessary X-rays.

Point-of-care ultrasound is increasingly being explored in emergency departments as well, where the speed advantage over waiting for an X-ray is especially appealing.¹⁷ The main barriers are operator skill and the learning curve involved. Ultrasound is not yet a replacement for X-ray in most hospitals’ protocols, but it is moving from experimental curiosity to practical bedside tool.

Electromagnetic-Guided Placement

Rather than placing the tube blindly and verifying afterward, electromagnetic tracking systems aim to guide the tube in real time. Devices like the CORTRAK system use a sensor at the tube tip that generates an electromagnetic signal, which a receiver translates into a visual display of the tube’s path on a screen. The clinician watches the tube’s progress and can stop or redirect if it appears to be heading toward the lungs.

A multicenter study compared electromagnetic-guided insertion to standard blind insertion and found comparable success rates: about 63% for the electromagnetic group and 66% for the blind group. The electromagnetic group did require fewer reinsertions and took less time per insertion (about 3.3 minutes versus 4.5 minutes).¹⁸ A separate feasibility study of an electromagnetic tracking device for small-bore feeding tubes reported no lung placements in 58 successful insertions, with almost complete agreement between the device’s readings and follow-up X-rays.¹⁹ The technology is promising for preventing pulmonary misplacement specifically, though the cost and equipment requirements limit its availability to larger centers.

How Positioning Affects Insertion Success

The measurement you take before insertion only works if the tube follows the expected anatomical path. Patient positioning during insertion affects how easily the tube navigates through the nasal passage, past the throat, and into the esophagus. In intubated patients, who often have a breathing tube already occupying part of the airway, getting the NG tube into the esophagus on the first attempt can be especially difficult.

A study comparing three positioning approaches in intubated patients found striking differences. Using a standard sniffing position (the default), first-attempt success was only about 33%. Adding neck flexion raised that to 55%. The best results came from using the standard sniffing position combined with lateral neck pressure, which achieved 85% first-attempt success and a 97.5% overall success rate within two attempts. Complications also dropped sharply with the lateral pressure technique, from 50% in the standard group to just 7.5%.²⁰ For non-intubated patients who can cooperate, sitting upright and swallowing sips of water during insertion remain the simplest ways to help the tube pass smoothly.

When Prior Surgery Changes the Rules

All of the measurement methods described above assume relatively normal anatomy. Patients who have had previous abdominal or esophageal surgeries may have altered internal pathways that make standard depth predictions unreliable or even dangerous. After a Roux-en-Y gastric bypass, for example, the stomach has been divided into a small pouch and a bypassed remnant. Inserting a standard-length NG tube in such a patient risks perforating the surgical pouch or anastomosis. A case report highlighted that the risk for perforation is increased in patients with prior abdominal surgeries, connective tissue disorders, or inflammatory bowel disease, and called for extreme care during placement in these populations.²¹

Patients with esophageal strictures, hiatal hernias, or esophageal varices also require modified approaches. In these cases, the question is not just “how far should the tube go” but “should the tube go in at all without direct visualization?” Endoscopic guidance or fluoroscopy may be safer than blind insertion in high-risk patients, regardless of how carefully the external measurement was performed.

Institutional Compliance and Why Protocols Matter

Knowing which measurement method is best and which verification technique to use matters less than whether the hospital actually enforces a consistent protocol. Data from the United Kingdom’s National Health Service illustrated this starkly. In the two and a half years after a national safety alert about NG tube placement was issued, 210 further incidents were reported, including 26 where enteral feed was delivered into the lungs. Five of those 26 patients died and six more suffered severe harm. In ten of those cases, checks had apparently been carried out, either X-rays or pH testing, yet the tube was still in the wrong place.²² The overall rate of serious events barely changed after the alert.

Quality improvement efforts that bundle measurement, verification, and documentation together tend to perform better than guidelines that simply recommend a technique. One hospital’s stroke unit trialed an NG tube bundle that included a standardized form, information poster, and nursing sticker. Guideline adherence rose to 83% of cases during the trial period.²³ A cross-comparison of Pennsylvania hospitals’ verification practices similarly concluded that the key risk reduction strategy is simply using recommended methods consistently and avoiding outdated ones like the whoosh test.²⁴ The evidence suggests that the single biggest risk factor for NG tube harm is not which measurement method a hospital endorses but whether bedside staff actually follow any verified method consistently every time.

Practical Steps for Getting It Right

If you are placing an NG tube, the research points to a handful of concrete actions that reduce risk. For adult patients, add at least 10 cm to whatever the NEX measurement gives you. Better yet, use a height-based formula if your institution has adopted one, and treat any external measurement as an estimate, not a guarantee. For children, switch to NEMU or an age-related height-based method instead of NEX. For neonates, use weight-based formulas appropriate to the infant’s size category.

After insertion, verify placement using pH testing first if aspirate is obtainable and the pH is 5.5 or below. If aspirate cannot be obtained or the patient is on acid-suppressing medication, obtain an X-ray. Do not rely on auscultation. If your unit has access to point-of-care ultrasound and trained operators, it can serve as a useful adjunct, particularly using the dynamic fogging technique, though it should not yet replace X-ray in equivocal cases. Mark the tube at the nostril after confirmed placement so that any migration can be detected later.

For patients with prior gastrointestinal surgery, esophageal disease, or any condition that alters normal anatomy, consult with the surgical or gastroenterology team before attempting blind insertion. Standard depth measurements assume standard anatomy, and these patients do not have it. Electromagnetic guidance or endoscopic placement may be the safest route.