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Invasive devices & lines

Up Bones Diaphragm Heart & great vessels Invasive devices & lines Lungs Major airways Mediastinum Pleura

Gavin Joynt

Nasogastric tubes

Most NGTs are about a few mm to1cm in diameter with a single thick radioopaque line. A gap in the line shows the position of side ports proximal to the tip. Both end and side port should be in the stomach. The most dangerous malposition is placement in the bronchus. CXR is the definitive method of ensuring correct position prior to feeding.

Chest drains

  • ~1cm diameter thick walled tube
  • radiographically similar to a thick NG tube. Single radio-opaque line with a break at the position of side ports
  • should be positioned through a latero-inferior skin puncture site with the distal tip placed superiorly within the pleural space for drainage of air, inferiorly for drainage of fluid
  • all side holes should lie within the pleural space

The chest drain is mispositioned: the side-hole of the drain lies outside the pleural cavity

Central Venous Lines

  • appear as smaller, 2‑3mm completely radioopaque catheters
  • in the thorax tip should lie in superior vena cava, midway between the azygous vein and right atrium
  • look for associated complications eg pneumothorax or haemothorax

The tip of the left subclavian line lies in the thoracic duct

The tip of the subclavian line is appropriately positioned but there is a line related pneumothorax. The nasogastric tube is incorrectly placed in the hiatus hernia instead of the stomach.


Text © Gavin Joynt, June 2005; images © Charles Gomersall, June 2005

©Charles Gomersall, January, 2018 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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