Chest X-ray - Tubes
CV Catheters - Position

Key points

  • The carina is clearly visible on most chest X-rays and so is used as a landmark to help determine central venous catheter (CVC) location
  • Correct positioning of a CVC tip depends on the side of entry
  • Correct positioning of a CVC tip also depends on the intended use of the catheter
  • Identifying the exact position of a catheter tip is limited by the quality of the X-ray

Catheter positioning

Positioning the tip of a central venous catheter (CVC) within the superior vena cava (SVC) at or just above the level of the carina is generally considered acceptable for most short-term uses, such as fluid administration or monitoring of central venous pressure. Ideally the distal end of a CVC should be orientated vertically within the SVC.

CVCs placed for the purpose of long term chemotherapy may be placed more inferiorly at the cavo-atrial junction - the junction of the SVC and right atrium (RA). Catheters used for haemodialysis may be placed at the cavo-atrial junction or even in the RA itself.

Positioning the catheter tip too proximally, for example in the right or left brachiocephalic veins, is associated with increased risk of line infection and thrombosis.

Anatomy

The lower part of the SVC is surrounded by the pericardial reflection; this is where the upper pericardium folds back on itself to form a sac. Positioning a CVC tip within the SVC and below the level of the pericardial reflection is associated with a small risk of pericardial tamponade.

Neither the SVC nor the pericardial reflection are visible on a chest X-ray. As the carina is a visible structure, which is located above the level of the pericardial reflection, it can be used as an anatomical landmark to help determine the level of a CVC tip within the SVC and above the pericardial reflection.

Superior vena cava (SVC) anatomy

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Superior vena cava (SVC) anatomy

  • The internal jugular and subclavian veins join to form the brachiocephalic veins (asterisks)
  • The brachiocephalic veins (also known as the innominate veins) join to form the SVC
  • The SVC is located to the right side of the mediastinum above and below the level of the carina

SVC anatomy - detail

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SVC anatomy - detail

  • The pericardial reflection is located below the level of the carina
  • The cavo-atrial junction is located approximately the height of two vertebral bodies below the level of the carina

Right-sided catheters

CVCs are most commonly inserted via the right internal jugular vein. Right internal jugular catheters are positioned on the right side of the neck, and pass vertically from a position above the clavicle.

Right internal jugular vein catheter

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Right internal jugular vein catheter

  • The catheter is orientated vertically
  • The tip is projected over the anatomical location of the SVC - approximately 1.5 cm above the level of the carina
  • This is an ideal position for right-sided catheters for fluid administration and venous pressure monitoring, but not for long-term chemotherapy or dialysis

Catheters inserted into the subclavian vein pass below the clavicle and then curve into the SVC.

Right subclavian vein catheter

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Right subclavian vein catheter

  • The catheter passes below the level of the clavicle
  • The distal catheter is orientated vertically
  • The tip is located 1 cm above the level of the carina

Left-sided catheters

Left-sided catheters approach the SVC at a shallow angle such that they may abut the right lateral wall of the SVC (see next page). They may need to be inserted further so the distal end obtains a vertical orientation. This may mean locating the tip below the level of the carina. In this position the risk of vessel wall erosion is reduced, but with a small increased risk of pericardial tamponade.

Left subclavian vein catheter

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Left subclavian vein catheter

  • This left subclavian catheter is located with its tip below the level of the carina
  • Positioning the tube vertically avoids abutment of the tip against the right lateral wall of the SVC

Long-term catheters

Catheters which are used for long-term administration of chemotherapy drugs (inserted either from the right or left) are usually positioned more inferiorly, at the level of the cavo-atrial junction. These catheters are usually inserted by radiologists or other specially trained staff.

Long term catheter - PICC line

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Long term catheter - PICC line

  • This peripherally inserted central catheter (PICC) is correctly located with its tip at the level of the cavo-atrial junction - approximately the height of two vertebral bodies below the level of the carina
  • This is often considered a preferable location for long-term catheters

Radiographic quality

Obtaining good quality X-rays in patients with CVCs is often technically difficult. Variance of radiographic quality factors, such as patient rotation or incomplete inspiration, means that identifying anatomical landmarks is often difficult. If in doubt about catheter location, ask a senior colleague or a radiologist.