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What is the blue thing at the end of an ng tube?

Nasogastric tubes, commonly referred to as NG tubes, are frequently used in healthcare settings to deliver nutrition, fluids, and medications directly into a patient’s stomach. These tubes are inserted through the nasal cavity, past the throat, and down into the stomach. At the end of an NG tube is a blue plastic device called an NG tube bolster that helps keep the tube in place and prevents it from migrating further into the stomach.

What is an NG Tube Bolster?

An NG tube bolster, also sometimes referred to as an NG tube bumper or NG tube anchor, is a small plastic device about the size of a quarter that is threaded onto the end of the NG tube once it is correctly positioned in the stomach. The bolster is blue so that it is easy to recognize. It serves several important functions:

  • Anchors the NG tube in place – The bolster is too large to pass through the opening of the stomach into the pylorus and small intestine. This helps prevent the tube from migrating down further than intended.
  • Secures the NG tube to the patient’s nose – Special tape or adhesive is used to secure the protruding end of the NG tube to the patient’s cheek or nose. This prevents the tube from slipping out.
  • Indicates proper tube placement – Seeing the blue bolster protruding from a patient’s nostril is a quick visual confirmation that the NG tube is correctly positioned in the stomach.
  • Allows administration of feeds/medications – Having the anchored bolster in place allows fluids, liquid nutrition, and medications to be given through the NG tube directly into the stomach.

The NG tube bolster is a simple but vital component that makes nasogastric feeding and medication administration possible. Most NG tubes will come packaged with an accompanying blue bolster specifically designed to fit that tube size.

How Does the Bolster Work?

The NG tube bolster works by essentially clamping the distal end of the NG tube where it emerges from the patient’s nostril. This is made possible by the bolster’s tapered shape.

The bolster has a narrow cylindrical hole through the middle that allows the tube to pass through. However, the opening is sized such that it creates friction against the tube walls. This is what creates the anchoring effect.

To thread an NG tube through the bolster:

  • Lubricate the tip of the NG tube with water or lubricant to help it slide through the opening
  • Gently insert the NG tube through the hole in the bolster
  • Continue threading it through until the bolster sits at the measured distance marking on the NG tube

This measured marking indicates how far the tube should be inserted. Having the bolster positioned at this marking is crucial for proper placement.

Once in place, the tapered walls of the hole create friction on the tube exterior to prevent sliding or migration. The bolster is soft enough, however, that the NG tube can still slide back and forth slightly through it as needed for repositioning.

Material and Design

NG tube bolsters are most commonly made of flexible plastic, usually polyethylene or silicone. This allows the opening to maintain close contact with the tube exterior.

Some key design features help bolsters serve their purpose:

  • Tapered shape – As mentioned, the tapered shape allows the hole opening to create optimal friction.
  • Beveled edges – Angled outer edges ensure no sharp corners irritate the nasal/lip area.
  • Larger than nostril opening – A diameter wider than the nasal cavity prevents passage into the stomach.
  • Thin walls – Thin plastic walls maintain a pliable, soft feel.
  • Color coding – Blue dye aids quick visual identification.

These attributes allow an effective grip on the NG tube while remaining gentle on patients.


NG tube bolsters come in a range of sizes to properly fit various diameter NG tubes. Tubes are sized using the French scale, with each French unit equaling 0.33 mm diameter.

Common sizes include:

NG Tube French Size NG Bolster Inner Diameter
8 2.6 mm
10 3.3 mm
12 4.0 mm
14 4.6 mm
16 5.3 mm
18 6.0 mm

Using a bolster specifically sized for the NG tube is important for a snug fit. The tube packaging or specifications will indicate what size bolster is needed.

Placement of the NG Tube Bolster

Proper positioning of the NG tube bolster on the tube is crucial for accurate feeding into the stomach. Placement steps include:

  1. Insert the NG tube through the nose to the predetermined depth marked on the tube for stomach placement.
  2. X-ray or pH testing of aspirate may confirm gastric positioning.
  3. Thread the bolster onto the protruding end of the NG tube.
  4. Slide the bolster down to align with the marked measurement on the tube.
  5. Secure the NG tube to the patient’s face with tape.
  6. Confirm external bolster placement with x-ray if necessary.

Having the blue bolster precisely aligned with the measurement markings prevents the tube from slipping too far down and coiling in the stomach. Protocols typically specify placing the bolster 5-10 cm from the nasal opening.

Replacing the NG Tube Bolster

Over time, the plastic bolster may wear out or become cracked. A worn out bolster may no longer maintain secure contact with the NG tube. If feedings or medications seem to be leaking out around the base of the bolster, it likely needs replacement.

Additional reasons the bolster may need replacing include:

  • Tube replacement is needed and existing bolster doesn’t fit new tube
  • Bolster has become loose or slipped out of place
  • Cracking or tearing of the plastic
  • Lost or misplaced bolster

To replace the NG tube bolster:

  1. Obtain a new bolster designed specifically for the tube size in use.
  2. Remove any tape securing the tube.
  3. Carefully snip and remove the old bolster from the tubing.
  4. Thread the new bolster onto the NG tube tip.
  5. Reposition it at the measurement marking.
  6. Retape the NG tube to the patient.
  7. Confirm correct placement.

Replacing the bolster quickly restores security and function. Bolsters are an inexpensive component easily changed on an as needed basis.

Risks of NG Tube Bolster Problems

Like any medical device, issues can sometimes arise with NG tube bolsters. Potential risks include:

  • Tube feeding leakage – A loose or ill-fitting bolster may allow stomach contents to leak from around the base of the tube.
  • Bolster slipping into stomach/intestines – A detached bolster can potentially slip down and cause intestinal obstruction.
  • Tube migration – Lack of secure bolster anchoring can allow the NG tube to shift downward into the intestines.
  • Necrosis of nasal tissue – An over-tightened bolster can exert excessive pressure on nasal tissue, resulting in tissue damage.

Using properly sized bolsters changed per protocol helps minimize risks. But care providers must continually monitor for signs of complications.

Alternatives to NG Tube Bolsters

Though NG bolsters are commonly used, there are a few other options for securing NG tubes:

  • Internal retention ring – Some tubes have an internal retention bumper or balloon near the tip that prevents downward migration.
  • Adhesive patches – External patches stick to the face to anchor the exposed tubing.
  • Taping methods – Special taping techniques, like a bridle tape, may be used to secure the NG tube.

However, NG tube bolsters remain the predominant method used. When changed per protocol, they provide an inexpensive, low-profile, and effective means of securing NG tubes.


The small blue bolster attached to the protruding end of an NG tube serves important anchoring and positioning functions. This tapered plastic component creates friction on the tubing to hold it in place, while also preventing internal migration. A properly sized and positioned NG tube bolster secures the tube for delivering nutrients, fluids, and medications directly into the stomach. Being aware of proper bolster placement and replacement guidelines is important for safe NG tube management.