Why is the external jugular vein not routinely used to assess the JVP?

The external jugular vein is not routinely used to assess the JVP because, although it is superficial and easily visualized, it is prone to kinking, which can give misleading results. The internal jugular vein is preferred because its pulsation reflects right atrial pressure more reliably.

According to the text, the external jugular vein is more superficial and can be easily seen, but it should not be routinely used to assess the jugular venous pressure because it is prone to kinking. Kinking can produce misleading results. The internal jugular vein is used for JVP assessment despite being deep, because its height is directly related to right atrial pressure, and its pulsation, though diffuse rather than clearly outlined, is a more reliable indicator.