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Module title = Tutorial: Lung Ultrasound
Lesson title = Pneumothorax
This is lesson 7 of 8 in this module
Lung Ultrasound – Pneumothorax
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Created by Dr. Danny Peterson, Dept of Emergency Medicine, University of Calgary.
Detection of pneumothorax
1,2
by ultrasound:
sensitivity 98%, specificity 95%
by chest x-ray:
sensitivity 67%, specificity 85%
Probe Selection:
A high frequency probe (10-12 Mz.) for high resolution is best. T
he linear array probe is best for assessing pneumothoraces.
Phased array is
not good
for pneumothorax.
Phased array is
not good
for pneumothorax
Linear array
is good
for pneumothorax
Step 1 - Position the patient and probe
position the patient supine (air will rise to anterior chest)
place probe in midclaviular line, 2nd or 3rd intercostal space
orient the probe with the
marker facing the patient's head
air is lighter than lung tissue. Therefore, it will be anterior when the patient is supine (on their back)
therefore, detection of pneumothorax by ultrasound is most sensitive by scanning the anterior chest
Step 2 - Optimize your intercostal space and ribs
Slide the transducer caudad & cephalad to maximize the intercostal spaces on the screen
do not need to sweep, as you would when scanning the abdomen
adjust your depth to optimize visualization of the pleural line (likely < 6 cm)
Step 3 – Identify the Pleural Line
the images seen "above" the pleural line are not artifact (ribs, muscle, fat)
there is a lot of reflection and scatter of the ultrasound waves by air
therefore, the images seen "below" the pleural line (lung) is mostly artifact
in the image below, a mirror artifact of the rib is also seen within the lung
A lines:
A lines are generated between the U/S probe and the pleura
A lines can exist with pneumothorax
presence or absence of A lines is non-contributory to the diagnosis of pneumothorax.
Lung Sliding
lung sliding is a normal finding
relative to the ultrasound probe, the chest wall does not move, but the lung does
Here is an example of lung sliding:
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Here is an example
of
ABSENT
lun
g sliding:
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if you can see lung sliding, there is no pneumothorax
absence of lung sliding
is suggestive but not diagnostic
of a pne
umothorax
other causes of absent sliding lung include:
pleurodesis or scarring (lung is stuck to the chest wall)
severe COPD (lung tissue might be bullous and not moving much)
severe consolidated pneumonia (no air going in and out of the lung = no movement)
Comet Tails and B lines:
comet tails and B lines are generated
only when the parietal and visceral pleural surfaces interact with each other
if there is a pneumothorax, then the pleural surfaces will be separated and will not interact with each other
therefore,
comet tails and B lines will be absent with pneumothorax
if you have
B lines and no lung sliding
, then there is no pneumothorax. Think about this for a second: B lines indicate pleural surface interaction; therefore, this combination is suggestive of
pleurodesis or severe consolidated pneumonia
review the video above: there are no comet tails or B lines and there is also no lung sliding
Lung Point:
the lung point is the edge of the pneumothorax
the larger the pneumothorax is, the more lateral and posterior it will extend
therefore, the further lateral and posterior the lung point is, the bigger the pneumothorax is
M-Mode signs:
we will discuss 2 signs found on M mode for lung ultrasound:
Seashore (Waves on the Beach) sign
Barcode sign
Seashore (Waves on the Beach) Sign
the seashore sign is a
normal finding
and represents lung sliding
the thick bright white line on the tracing is the pleural line
superficial to the pleura (chest muscles, skin, fat) is not moving, creating the solitary linear lines indicating a lack of motion
deep to the pleura is lung sliding causing irregular grainy artifact
Now use your imagination: the superficial (top) part of the image looks like waves approaching the beach. The pleural line is the surf break. The deeper (bottom) part of the image looks like the sand on the beach. Go grab your Speedos!
Barcode or Stratosphere Sign
when there is no movement, M mode creates straight lines (as in the ocean above)
if there
is
no lung sliding
, then
there is no movement
anywhere on the screen
the barcode sign occurs when when lung sliding is absent
the barcode or stratosphere sign is an
abnormal finding
tip a barcode on its side to see the similarities (this is the barcode from my pair of men's Speedos
Conclusions:
Presence of
lung sliding
rules out a pneumothorax at that location.
Presence of
comet tails
or
B lines
rules out a pneumothorax at that location.
Presence of
lung pulse
rules out a pneumothorax at that location.
Absence
of the following are
all required
for Dx of pneumothorax:
Lung sliding
Comet tails
B lines
Lung pulse
Absence of lung sliding with
presence
of comet tails, B lines or lung pulse suggests important pathology other than pneumothorax.
The lung point helps determine size/location of the pneumothorax.
Presence or absence of A lines is non-contributory to the Dx of pneumothorax.
Lung sliding in M mode = Seashore sign.
Absense of lung sliding in M mode = Stratosphere or Barcode sign.
References
Lichtenstein, D; Mezier, G, Bidman, P; Gepner, A. The “lung point”, an Ultrasound sign specific to pneumothorax. Intensive Care Med 2000:26 (10) 1434-40
Blaivas, M; Lyon, M, Duggal S. A Prospective Comparison of Supine Chest Radiographs and Bedside Ultrasound for the Diagnosis of Traumatic Pneumothorax. Acad Emerg Med 2005; 12(9); 844-9
Lesson 7 of 8
That was the last lesson!