Measuring a nasogastric (NG) tube for a baby involves stretching the tube along external body landmarks to estimate how far it needs to reach the stomach. The most widely recommended method today is called NEMU, which measures from the nose to the ear to the midpoint between the bottom of the breastbone and the belly button. Getting this measurement right is critical: too short and the tube sits in the esophagus, too long and it curls past the stomach.
The NEMU Method Step by Step
NEMU stands for Nose-Ear-Mid-Umbilicus. You hold the tip of the tube at the baby’s nose, stretch it to the bottom of the earlobe, then continue down to the midpoint between the xiphoid process (the small bony point at the very bottom of the breastbone) and the umbilicus (belly button). The spot where the tube reaches that midpoint is your estimated insertion length.
An older technique called NEX stops at the xiphoid process instead of continuing to the midpoint with the belly button. NEX has been shown to underestimate insertion length, leaving tubes too high in the esophagus rather than safely in the stomach. In one study, the NEX method placed only about 61% of tubes correctly, while NEMU placed roughly 91% correctly. Because of this, many neonatal guidelines now recommend NEMU over NEX. Once you’ve determined the correct length, mark that point on the tube with a small piece of tape or a permanent marker so you have a visible reference for where the tube should sit at the nostril.
Length-Based Charts for Neonates
For newborns under one month corrected age, body length provides a more precise estimate than external landmark measurement alone. A regression formula developed specifically for this age group calculates insertion length as 1.95 cm plus 0.372 multiplied by the baby’s length in centimeters. In practice, clinicians use a chart derived from that formula rather than doing math at the bedside:
- 35–35.5 cm baby: 15 cm insertion length
- 38.5–39.5 cm baby: 16.5 cm
- 40–41 cm baby: 17 cm
- 44–45 cm baby: 18.5 cm
- 48–49 cm baby: 20 cm
- 51–51.5 cm baby: 21 cm
- 55–55.5 cm baby: 22.5 cm
For very small premature infants, earlier research suggested minimum insertion lengths based on weight: 13 cm for babies under 750 grams, 15 cm for those 750 to 999 grams, 16 cm for 1,000 to 1,249 grams, and 17 cm for 1,250 to 1,499 grams. These serve as starting references, but the length-based chart above is generally considered more accurate when a reliable body length measurement is available.
Choosing the Right Tube Size
NG tubes are measured in French gauge (Fr), where a higher number means a wider tube. For babies, size selection is based on weight:
- 2 kg: 6 Fr
- 3–9 kg: 8 Fr
- 10–20 kg: 10 Fr
Using a tube that’s too large for a baby’s nostril can cause tissue damage or block the airway on that side, which matters because infants are obligate nose breathers in the early weeks. If a baby needs a larger tube for surgical reasons, switching from nasal to oral placement (an orogastric tube) may be necessary to avoid nasal obstruction. For routine feeding purposes, nasogastric tubes placed through the nose are standard.
Nasogastric vs. Orogastric Measurement
Orogastric (OG) tubes go through the mouth instead of the nose. The measurement technique is similar, but the starting point is the corner of the mouth rather than the tip of the nose, which results in a slightly shorter insertion length. One formula used in neonatal units estimates OG insertion distance as 13.3 cm plus 0.19 multiplied by the baby’s length in centimeters, compared to 14.8 cm plus 0.19 for NG tubes in the same population. The difference is roughly 1.5 cm, reflecting the shorter distance from mouth to esophagus compared to nose to esophagus.
Why Accurate Measurement Matters
A tube placed too short can sit in the esophagus, where feeding or medication would cause aspiration into the lungs or reflux. A tube placed too deep can pass through the stomach into the small intestine, coil, or cause irritation. In neonates, the margin of error is small because the total distance from nose to stomach may be only 15 to 23 centimeters.
Pulmonary misplacement is the most dangerous complication. In one documented neonatal case, a tube that entered the right main bronchus caused a pneumothorax (collapsed lung) and a bronchopleural fistula, requiring chest drainage and ventilation. These events are rare but underscore why placement verification is not optional. An X-ray remains the gold standard for confirming that the tube tip is in the stomach, particularly after initial placement. Even after a malpositioned tube is removed, a follow-up chest X-ray may be needed to rule out lung injury.
Verifying and Monitoring Placement
After insertion, the external mark you placed on the tube tells you how much tube is outside the body. Check this mark regularly, because babies move, and tubes can migrate. If the mark shifts outward, the tube has likely pulled back and may no longer be in the stomach.
Aspirating a small amount of stomach contents and testing the pH is a common bedside check. Gastric fluid typically has a pH below 5.5. The old method of injecting air and listening with a stethoscope over the stomach is unreliable in infants, as sounds from a tube in the esophagus or lungs can mimic gastric placement. X-ray confirmation is recommended for initial placement and any time there’s doubt about position.
Supplies You’ll Need for Measurement
Before starting, gather the correctly sized tube, hypoallergenic tape or an approved securement device, a permanent marker or small tape strip for marking insertion length, water-soluble lubricant, clean gloves, a stethoscope, and a pulse oximeter to monitor the baby’s oxygen levels during the procedure. Lubricate the tip of the tube about 2 to 3 inches with water-based lubricant before insertion. Do not use oil-based lubricants, as they can damage lung tissue if aspirated.