Study with patient at 45°
Find the meniscal level at end expiration
Measure height from sternal notch and add 5cm for pressure in cmH20
American Journal of Emergency Medicine 2000;18(4):432)
ULTRASOUND OF NECK VEINS WITH NORMAL CVP
As the patient with a normal CVP (0 to 10 cm of H2O)
assumes a semiupright position, the pressure in the jugular
vein falls. At some point in the neck, the extravascular tissue
pressure is greater than the local venous pressure and the
vessel collapses. In the longitudinal plane, the shape of the
IJV in this transitional zone resembles a wine bottle with a
wide inferior base tapering to a narrow superior neck (Figure
3). It is in this tapering portion of the IJV that the vein walls
will appear to flutter in real-time. This is the site of the
jugular venous pulse. The most superior point of this
tapering portion is the location of vein collapse and is the
sonographic equivalent of the top of the column of blood in
the jugular vein. Occasionally, this point has been referred to
as a ‘‘meniscus.’’2 It is an inaccurate analogy, because a true
meniscus does not exhibit this tapering shape. In the sitting
position, the patient with a normal CVP will have an IJV that
is almost completely collapsed. In the transverse plane it will
either be nonvisualized or appear as a small crescent or slit
(Figure 4). The IJV will transiently distend with forced
expiration or Valsalva but will promptly collapse with
normal respiration. In the semiupright position with a
normal CVP, the top of the column of blood will be inferior
to the clavicles and the IJV will be collapsed in the middle of
the neck. The reclining angle must be lowered until the IJV
becomes distended. The vein should be visualized by
scanning the neck in the transverse plane. The probe is then
moved in a superior direction on the neck to locate the point
of vein collapse. The point under the transducer on the neck
is marked. The vertical distance in cm between this point and
the angle of Louis is measured; 5 cm is added to obtain the
estimated CVP.
ULTRASOUND OF NECK VEINS WITH ELEVATED CVP
If the CVP is elevated above 10 cm of H2O, the IJV
becomes distended, even in the semiupright position. Scanning
the midneck in the transverse plane, the IJV will
assume an oval or round appearance. With the patient in a
semiupright position it will appear as large or larger than the
adjacent CCA (Figure 1). Occasionally, a patient with an
extremely elevated CVP (above 20 cm of H2O) must be
scanned in the standing position to locate the point of vein
collapse between the clavicle and the angle of the mandible.
Again, the vertical distance between the point of collapse
and the angle of Louis is measured; 5 cm is added to obtain
the estimated CVP.
ULTRASOUND OF NECK VEINS WITH LOW CVP
If the CVP is very low (less than 0 cm of H2O) the vein
will appear almost collapsed, even in the supine position.
The sonographic appearance will be similar to the patient
with a normal CVP in the upright position (Figure 4).
TECHNICAL POINTS
Several caveats are important when scanning the IJV.
Veins are low-pressure vessels and when located superfi-
cially are easily compressed. Gentle pressure with the
transducer is all that is necessary; too much pressure will
collapse the vein and mislead the clinician. Because the
examination is performed in real-time, any operator-induced
collapse should be obvious. If a high frequency transducer is
not available, a lower frequency probe (5 MHz) may be
substituted, but image resolution will be poorer. Image depth
must be decreased manually to optimally visualize superfi-
cial structures. The vessels should be scanned with the head
in a neutral position, as the IJV tends to collapse with
extension of the neck.12 The point of collapse may fluctuate
up and down slightly with normal respiration, as pressure in
the central veins is affected by intrathoracic pressure. There
is usually a fall of the point of collapse of several cm on
normal inspiration.7,13 Mark the point in the neck at endexpiration;
this is the same phase of respiration that the CVP
is measured with a central catheter and pressure transducer.14
Position the patient so the point of vein collapse is located in
the middle third of the neck. The IJV, even with a normal
CVP, may be distended at the base of the neck. This is
because the vessel is ‘‘splinted’’ open by the negative
intrathoracic pressure as it enters the chest cavity. This is
also where thin, mobile valves in the IJV are often located.
e thyroid gland is located medial to the vessels low in the
neck. Cysts and nodules are common and are usually
clinically insignificant. Always start by scanning the right
IJV but confirm findings by examining the contralateral
vein. If the patient has had previous neck surgery, IJV
cannulation, or irradiation, the vein may not distend normally
with elevated pressure.
ROLE OF JUGULAR VENOUS ULTRASOUND
Ultrasound of the internal jugular vein is probably the
easiest examination for the novice sonographer to master.
However, not every patient needs an ultrasound examination
of his or her jugular vein. As clinicians, it is important to
perform an adequate visual inspection of the jugular pulse.15
Nonetheless, there are situations with some patients where
the physical examination does not furnish the information
needed. Bedside sonography performed by emergency physicians
provides immediate, important information that
would otherwise require the use of invasive catheters.