I often get asked the question about how to identify the internal jugular vein for measuring the Jugular Venous Distension (pressure).
It is sometimes not so easy to be able to identify by just positioning the patient.
Interestingly, in some US based examination texts, they mention that the patient should be positioned at 30 degrees. This concept is contrary to the traditonal way of checking the JVP which is at 45 degrees-- the UK standard.
Hence, with the patient at 45 degrees, they should turn their head to the left hand side thereby exposing the two heads of the sternocleidomastoid muscles (sternal head and clavicular head). The internal jugular vein should be seen to run between these two heads in an upward and anteroposterior incline.
The normal JVP is no more than 4cm H2O. This is measured in a vertical direction from the manubriosternal joint to the maximum height of the jugular venous pulse.
An estimated height is adequate because the most important thing is to identify if it is raised or normal i.e. just visible.
There are several different wave forms to the JVP, which although are described in the traditional physical examination textbooks, in everyday practise, only a few of them are clinically helpful.
If one is unable to idenfity the JVP by position at 45 degrees alone, then if the patient has no abdominal pain, try pressing on the liver and watch for a rise in the JVP. This is the hepatojugular reflex.
Moreover, the JVP has a double pulse compared to the carotid that has just one.
By positioning the patient vertically, the JVP should disappear (unless severe venous obstruction) whereas the carotid pulse does not. Conversely, by lying the patient flat, the JVP should then increase.
The JVP may sometimes be missed by the inexperienced eye particularly if the patient has a large neck with subcutaneous fascia. One other sign is to look for movement of the earlobe. With severely elevated JVP, with the large upstroke of blood in the internal jugular vein, it causes the earlobe, beneath which it runs, to move!
Why is the JVP important at all??
JVP is important because with the right clinical history, it may aid in the diagnosis of heart failure, atrial fibrillation, tricuspid regurgitation, cor pulmonale, PE, tamponade, iatrogenic fluid overload etc... Although it is relatively non-specific for the above conditions, it nevertheless gives the physician some idea that there is pathology occuring that requires further investigation.
For example, in a patient with slowly increasing breathlessness, dyspnoea on exertion and at rest, plus the complaint of bilateral leg swelling, the physical examination looking for the raised JVP and lung crackles would make one consider at least the common diagnosis of heart failure.
Conversely, sudden on onset of dypnoea, chest pain, haemoptysis, unilateral leg pain with an examination of a tachycardia, raised JVP and a clear chest would make most competent physicians consider a large pulmonary embolism.
I hope this helps!