Common carotid artery
This will hardly ever be visible and is usually assessed by means of palpation.
Jugular vein/CVP measurement
The internal and external jugular veins are directly connected to the heart: during systole they are connected to the right atrium and during diastole with the right atrium and the right ventricle (the tricuspid valve is then open). The non-visible internal jugular veins (without valves) are used for the direct blood pressure determination of central venous pressure (CVP) by means of a catheter. The external jugular veins (with valves) are located superficially and are used for the external determination of CVP. The determination of CVP provides an indication of the pressure and degree of filling of the right-hand side of the heart. An elevated CVP can, for example, be found in the case of pulmonary stenosis, pulmonary hypertension, pulmonary embolism and tricuspid insufficiency, but mainly also in the case of right ventricular dysfunction in relation to left ventricle disorders.
Various techniques can be used. Here a qualitative determination has been chosen that does not require the use of a ‘venous arch’.
Procedure
The patient should lie on the examination table in the supine position. The head end of the table should be elevated at a 45-degree angle. The head and thorax of the patient should rest here while the measurement is being taken. The patient should then turn their head slightly to the left so that the external jugular vein is clearly visible [Figure 3].
Figure 3: Right external jugular vein is clearly visable when the head is turned slightly to the left
Then the extent to which the jugular vein is filled should be examined. Next, the collapse point (the exact point where the vein is no longer filled) should then be located and compared with the sternal angle. For a normal CVP, when measured vertically (in other words from the ground upwards) the collapse point should not be more than 2 to 4 cm above the sternal angle [Figure 4].
Figure 4: Comparison of the collapse point with the sternal angle
Comments
Sometimes pulsations in the jugular vein can make it difficult to determine the precise collapse point. This can be solved by compressing the cranial jugular vein (at the patient’s head) and then emptying it by stroking it in a downwards direction using the index finger of the other hand. The collapse point then becomes more clearly visible.
Often the visible part of the jugular vein in the neck is completely unfilled in this position. The collapse point is then located in the thorax and the CVP is not elevated.
In the case of a strongly elevated CVP the entire visible part of the jugular vein will be filled. The collapse point will then be somewhere in the head, and the CVP will be elevated.