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Module title = Tutorial: Lung Ultrasound
Lesson title = Pleural Effusion
This is lesson 6 of 8 in this module
Pleural Effusions
Normally there are 2-10 ml of fluid in pleural space.
In pathological conditions causing pleural effusions, the volume of fluid is increased. We can identify this fluid with non-invasive imaging:
upright CXR -
100 -150 ml
is required to blunt the costophrenic angle
supine CXR -
200 - 300 ml
is required to be identified
ultrasound
-
as little as 20 ml of fluid
can be identified
Probe Selection: a
low frequency probe (2-5 Mz.) for deeper penetration is best.
a smaller footprint is easier to get between ribs
the
phased array
("cardiac" probe) or the
curved array
("abdominal" probe) are good choices
do not use the linear array
("vascular" probe) - the images are too shallow
Phased array is good:
Curved array is good:
Linear array is not good:
Patient position
the patient can be either supine, semi-sitting or totally sitting up
raise the arm to increase space between the ribs
Step 1 – Palpate the xiphoid
place the probe with marker toward head on the
posterior axillary line
at the
level of the xiphoid
Step 2 – Locate the diaphragm
the diaphragm is a skinny, curved and bright white (hyperechoic)
if you are on the patient's right, you will see the liver below the diaphragm
if you are on the patient's left, you will see the spleen below the diaphragm
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Step 3 – Center the diaphragm
slide the probe toward (cephalad) or away from (caudad) the head to bring diaphragm into the center
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Step 4 – Identify the pleural cavity
remember that the orientation marker on the
screen
is on the left
the marker on the
probe
is toward the head
therefore, "screen left" = toward the head (cephalad)
the pleural cavity is cephalad to the diaphragm
therefore, the pleural cavity is to the left of the diagphragm on the screen
Step 5 – Sweep anterior and posterior to view
identify the region where the effusion is largest
select this space for inserting a needle or tube, if indicated
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Normal Lung findings
the lung is normally filled with air
air in lung scatters the ultrasound beam and therefore produces a snowstorm appearance
Effusions
fluid does not reflect ultrasound waves. Therefore, fluid is anechoic = black.
pleural effusions are black
frequently you will see
atalectatic (collapsed) lung
within the effusion. Lung without air takes on the appearance of a solid organ and will be white.
collapsed lung is white
if the lung is separated from the chest wall or diaphragm by more than 3 cm. of effusion, the pleural space contains at least 500 ml of fluid
The Spine Sign
Since the beam passes though the liver to the midline, it will often encounter a series of white lines representing the spine. Bone reflects all sound back to the probe, so deep to the white line will be shadowing.
since air does not transmit sound, you
will not be able to see the spine above the diaphragm
if there is pleural effusion, then there will be no air superior to the diaphragm as the lung is displaced by fluid
in this situation, the sound waves will be able to travel all the way to the midline, revealing the spine
if you can see the spine on the left of the liver/diaphragm, this finding supports the presence of a pleural effusion
Here is example of a normal ABSENT spine sign (no effusion):
Here is an example of a PRESENT spine sign with pleural effusion:
Here is a video showing a small effusion and the spine sign:
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Loculated Effusions:
Loculated complex effusion have a variety of appearances. Clotted blood and empyemas may take on the ultrasound characteristics of a solid organ.
Conclusions:
The pleural space is to the left of the diaphragm if screen marker on left and probe marker toward head
Liquid effusions are black
Effusions > 3 cm suggest effusion is > 500 ml
Collapsed lung (atalectasis) is white
Spine sign occurs with effusions
Loculated effusions will have white stranding
Clotted effusions or empyema can mimic a solid organ
Lesson 6 of 8
That was the last lesson!