Identification of the biphasic waveform of the JVP can be challenging. Here are some helpful tips:
Adjusting the angle of inclination
In contrast to the pulsation of the carotid artery, location of the JVP along the neck is dependent upon the angle of inclination of the patient. The usual angle of inclination initially used to attempt to detect the JVP is generally between 30-45 degrees. This positioning is adequate for JVP detection in a majority of patients, however may be insufficient for patients with marked hyper- or hypovolemia.
Patients that are hypotensive secondary to hypovolemia may have JVPs that are closer to 0 or 1 cm above the sternal angle. Detection of the JVP in these patients often requires for them to lie completely flat before a biphasic pulsation can be seen along the neck.
On the opposite end of the spectrum, the JVP in patients that are markedly volume overloaded may be so high that it cannot be visualized when patients are at 45 degree of inclination. In these patients, proper visualization often requires that patients be sat completely upright at a 90 degree angle and even with that relatively extreme positioning, the JVP may still be observed at the angle of the jaw.
Distinguishing the JVP from the carotid impulse
1. The high pressure carotid pulsation is palpable, whereas the JVP cannot be palpated owing to its being part of the low pressure venous system.
2. The JVP can be occluded causing the biphasic pulsation to extinguish by applying manual pressure over its course just above the clavicle, while the carotid pulsation cannot be occluded.
3. The carotid impulse is located medial relative to the JVP pulsation.
4. The biphasic JVP pulsation descends with inspiration, whereas the carotid pulsation remains unchanged.
5. The JVP is a biphasic pulsation, in contrast to the monophasic carotid pulsation.
6. Increasing the angle of incline of the patient relative to the horizontal causes the JVP pulsation to descend along the neck, while the carotid pulsation will remain unchanged.
A helpful mnemonic (POLICE) can be used to recall these points:
P (palpable) – O (occludable) – L (location) – I (inspiration) – C (contour) – E (elevation)
The abdominojugular, or alternatively hepatojugular, reflux involves applying pressure over the upper right quadrant of the abdomen in order to accentuate the pulsation of the JVP. This on its own can facilitate differentiation of the JVP relative to the carotid artery, given that the carotid artery pulsation will be unaffected by an increase in intra-abdominal pressure.
A positive abdominojugular reflux sign is considered an increase in the JVP of > 3 cm that persists for longer than 15 seconds. Any condition that prevents the right ventricle from accommodating increased venous return may result in a positive abdominojugular reflux sign.
When accessible, portable ultrasound can facilitate identification of the JVP through application of the ultrasound probe on the neck over the course of the internal jugular vein. The biphasic pulsation of the JVP will correspond visually on ultrasound to a “steeple sign”, whereby the vein collapses above the maximal height of the JVP. Following recognition of this site along the neck, its height above the sternal angle can then be ascertained.