Chest X-ray - Tubes
ET Tubes - Position

Key points

  • The tip of an endotracheal tube (ET tube) should be located in the trachea above the carina
  • To see the carina use a good quality screen in a darkened room

A chest X-ray is often acquired following placement of an endotracheal tube (ET tube) to determine the position of its tip.

The trachea, carina and main bronchi are almost always identifiable on a chest X-ray image, as long as the image is viewed on a high quality screen in a darkened room.

Tracheobronchial anatomy

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Tracheobronchial anatomy

  • The trachea is located on the right side of the aortic knuckle and slightly to the right of the midline
  • The carina is the point at which the lower edge of left and right main bronchi meet

Correct endotracheal (ET) tube position

As ET tubes are fixed at the mouth, neck position affects the location of the ET tube tip. Neck extension pulls the tube superiorly and neck flexion pushes the tube inferiorly. Neck rotation may also displace the tube.

On a radiograph acquired with the neck in the neutral position, a distance of 5-7 cm above the carina is generally considered acceptable for adults. In this position it is unlikely that the tube could be pushed beyond the carina or pulled towards the vocal apparatus.

Use the measurement tool provided by the digital viewing software and make sure the position is documented.

Correct ET tube position

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Correct ET tube position

  • The ET tube tip is correctly located in the trachea, 5 cm above the carina
  • Most ET tubes have an inflatable cuff which forms a seal against the trachea; these cuffs are not visible radiographically

Carina position

If the carina is not clearly visible, then the vertebral bodies can act as an anatomical landmark to estimate carina position. In most individuals the carina is located between the levels of the 5th and 7th thoracic vertebral bodies.

Note: This is an inaccurate method for locating the carina and if the patient is kyphotic or has a chest wall deformity, or if the image is a kyphotic or lordotic view, then this method should not be relied upon. Remember to look at the image on a high quality screen in a darkened room. If you still can't see the carina, then ask a senior colleague or a radiologist.

Carina position

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Carina position

  • The carina is more difficult to identify in this image so the vertebral bodies can be used as a rough estimate of carina position
  • If the vertebral bodies themselves are not seen clearly, as in this case, the ribs can be used as landmarks to locate the correct vertebral level, and hence the approximate level of the carina
  • If you look very carefully, the carina is faintly visible in this image, as is almost always the case

Tracheostomy tubes

Tracheostomy tubes are fixed at the skin by a flange located immediately anterior to the trachea. Therefore, the tip of a tracheostomy is less susceptible to change in position on neck flexion or extension than is the case for an ET tube.

Tracheostomy tubes are positioned so that their tips are located at a midpoint between the upper end of the tube and the carina.

Carina position

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Carina position

  • This tracheostomy tube tip is located 6 cm above the carina - approximately half the distance between the top of the tube and the carina