Verifying nasogastric (NG) tube placement requires confirming the tube tip sits in the stomach, not the lungs or esophagus. The gold standard is a chest and abdominal X-ray, but bedside methods like testing the pH of stomach aspirate play a critical role in ongoing checks. Getting this right matters: roughly 2 to 3 out of every 100 NG tubes end up in the airway, and respiratory complications from misplacement can be fatal.
Why Verification Is Critical
An NG tube that lands in the lungs instead of the stomach can cause pneumothorax (a collapsed lung), aspiration pneumonia, or death. Between 2005 and 2010, the UK’s National Patient Safety Agency documented 21 deaths and 79 serious events caused by displaced NG tubes. The US Food and Drug Administration recorded 51 reports of pneumothorax linked to NG tube placement over a five-year period. Respiratory complications are by far the most common category of NG tube harm, and patients who receive feeding through a misplaced tube are 15 times more likely to develop aspiration and face twice the mortality risk compared to those with correctly placed tubes.
These aren’t just risks during initial insertion. Tubes can migrate after placement due to coughing, vomiting, or simply moving in bed. That’s why verification isn’t a one-time event.
X-Ray: The Gold Standard
A chest and upper abdominal X-ray is the most reliable way to confirm initial placement. On the image, the tube should follow a specific path: it descends vertically along the midline (or just left of midline), passes below the point where the windpipe splits into the two main airways, and continues straight down through the diaphragm into the stomach. The tube must not veer to follow either airway branch.
The tip should be visible on the left side of the abdomen, at least 10 cm beyond the point where the esophagus meets the stomach. If the tip is higher than that, the tube may be coiled in the esophagus or sitting at the junction rather than reliably in the stomach. Radiographic confirmation is required before any feeding, medication, or flushing begins through a newly placed tube.
pH Testing at the Bedside
Once X-ray has confirmed initial placement, pH testing of aspirated fluid is the primary bedside method for re-checking position. A small amount of fluid is drawn from the tube and tested with pH indicator paper. Gastric fluid is acidic, typically falling at a pH of 5 or below. Respiratory secretions, by contrast, tend to be much more alkaline, averaging around 8.4 in studies of airway samples, with none dropping below 6.
A pH of 5 or lower is generally considered reliable confirmation that the tube tip is in the stomach. Some guidelines use a stricter cutoff of 4 or below. The difference matters in certain populations: patients taking acid-reducing medications may have a higher gastric pH, making aspirate harder to interpret. In those cases, if the pH result is ambiguous, an X-ray is the safest next step.
Getting a Good Aspirate Sample
Sometimes drawing back on the syringe produces nothing, which doesn’t necessarily mean the tube has moved. The tip may be resting against the stomach wall, or the tube may be kinked. Repositioning the patient onto their left side, gently advancing or withdrawing the tube by a small amount, or injecting a small air flush before reattempting aspiration can help. If you still can’t obtain aspirate and can’t confirm placement, do not use the tube until position is verified another way.
The “Whoosh Test” Is Not Reliable
The auscultation method, sometimes called the “whoosh test,” involves pushing air through the tube while listening over the stomach with a stethoscope. For decades this was routine practice, but it is now widely discouraged. One study found auscultation correctly identified tube position in only 34.4% of cases. The core problem is that air entering the lungs through a misplaced tube can produce sounds that are easily mistaken for stomach gurgling, especially in a noisy clinical environment. Another study reported high sensitivity (96%) but a specificity of just 17%, meaning it almost never correctly identified a misplaced tube. Major nursing and patient safety organizations no longer recommend this method.
CO2 Detection for Airway Misplacement
Colorimetric carbon dioxide detectors, the same small devices used to confirm breathing tubes during resuscitation, can be attached to the end of an NG tube after insertion. If the tube is in the airway, the device changes color (typically from purple to yellow) as the patient exhales carbon dioxide through it. A pooled analysis of 16 studies covering nearly 1,900 tube placements found this method had 96% sensitivity and 99% specificity for detecting respiratory placement.
This approach is useful as a quick safety check to rule out airway placement, but it doesn’t confirm the tube is in the stomach specifically. The tube could still be in the esophagus. CO2 detection works best as an additional layer of safety rather than a standalone method.
Ultrasound as an Emerging Option
Point-of-care ultrasound can visualize the NG tube in the stomach at the bedside without radiation. In comparative studies, ultrasound achieved 95.5% sensitivity and 100% specificity, slightly outperforming pH testing (90.9% sensitivity and 100% specificity) in the same patient groups. Ultrasound is particularly appealing in settings where repeated X-rays are undesirable, such as in pregnant patients or neonatal units. However, it requires a trained operator and isn’t yet universally adopted as a standard verification method.
Measuring Insertion Length
Before inserting an NG tube, the estimated length needed is traditionally measured using the NEX method: the distance from the nose to the earlobe, then from the earlobe to the bottom of the breastbone. This technique has been standard practice since 1951, but a meta-analysis covering all available evidence found it is accurate only about 72% of the time or less. The main concern is that NEX tends to underestimate the required length, leaving the tube tip too high, potentially in the esophagus rather than the stomach.
Because locating the bottom of the breastbone can be tricky, measuring in the reverse direction (breastbone to ear to nose) is sometimes easier. Regardless of the measurement method used, insertion length alone never confirms placement. It is a starting estimate, not a verification tool.
Ongoing Checks After Initial Placement
Tube position should be re-verified before every use, whether that’s a feeding, a medication dose, or a flush. For patients on continuous feeding, the American Association of Critical-Care Nursing recommends checking and documenting tube position every four hours. The two key bedside checks are measuring the visible external tube length (and comparing it to what was recorded at the time of the initial X-ray) and testing aspirate pH.
If the external length has changed, the tube may have migrated. If the patient develops any new respiratory symptoms, such as coughing, difficulty breathing, or a drop in oxygen levels, feeding and medications should be stopped immediately and the tube position reverified before anything else goes through it.
Special Considerations for Newborns and Children
pH testing is trickier in neonates. Newborns naturally have a higher stomach pH because they swallow amniotic fluid during birth and produce less stomach acid in the first days of life. This means a pH reading above 5 doesn’t necessarily indicate misplacement in this population, but it also makes the test less definitive. On top of that, neonates have very small gastric fluid volumes, making it physically difficult to withdraw enough aspirate for testing. X-ray confirmation carries greater weight in this age group, and clinicians often rely on it more heavily than bedside pH checks alone.