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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5836_Библиотеки_им_академика_М_И_Перельмана.pdf
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Figs. 4.3, 4.4, 4.5, and 4.6 Hemothorax. On the right of the fi gure, there is the texture of the solid
organ (spleen or liver). You may notice the bright, curved line of the diaphragm, and on the left
side (above the diaphragm) there is the fl uid. Note the collapsed lung appears “solid” with some
white spots (trapped air bubbles)
A.A. Casamassima and M. Zago
43
Figs. 4.3, 4.4, 4.5, and 4.6 (continued)
4 Thoracic Views: Anatomy, Techniques, Scanning Tips and Tricks, Abnormal Images
44
The probe will be applied longitudinally, on the midclavicular line, on the
uppermost area of the chest (your patient is in supine position) (Fig. 4.7 ).
You have to recall the anatomy of the chest wall. Think of it in layers: skin and
subcutaneous tissue, muscles, ribs, and pleura (Fig. 4.8 ).
When you apply the probe on the chest of the patient, the fi rst image you have to
look for is the “bat sign” (Fig. 4.9 ), an original way to describe normal US anatomy.
The bat sign is characterized by two ribs and their shadows and the pleural line.
As you can see in Fig. 4.9 , with a bit of imagination, you can see the wings of the
bat (the ribs with their acoustic shadow) and the back of the bat (the bright pleural
line), fl ying toward you.
This particular static sign allows us to know if our ultrasound exam will be con-
ducted properly: in fact if you’re not able to see the bold white line between the rib
shadows (pleural line), you cannot tell if there is a PTX.
(NB: properly, pleural line defi nes the visceral pleural interface sliding up and
down, so it is obviously not detectable if there is PTX, but to help you in familiar-
izing with chest US, let’s call pleural line the white line 1 cm below and between the
two rib shadows.)
Fig. 4.7 Position of the
probe on the chest when
scanning for PTX
Key landmarks
Rib shadow Rib shadow
Pleural line
Fig. 4.8 Scheme of a classic
US chest view for PTX: two
ribs with their shadows and
amidst them the pleural line
A.A. Casamassima and M. Zago
45
In trauma patient, we have to pay particular attention to subcutaneous emphy-
sema, since high acoustic impedance of the air in subcutaneous tissue will defl ect
the ultrasonic beam, preventing us to detect the bat sign and thus to perform the
exam.
Once we clearly see the pleural line, we can start the exam looking for a dynamic
sign called “sliding lung” or “gliding sign.”
The “sliding lung” can be described as a rhythmic sparkle of the pleural line,
moving synchronously with the breathing cycle of the patient.
It’s generated by the comet tail artifacts of the air in the outer alveoli, just beneath
the visceral pleura sliding on the parietal pleura (Fig.
4.10 ).
If you can detect the sliding lung, you can be sure there is no PTX.
In order to identify the sliding lung properly in diffi cult environment (i.e., bright
lights in ER refl ecting on the US machine screen), you can switch on the M-mode
(motion mode), and you’ll have a second useful dynamic sign: the seashore sign.
M-mode measures the intensity of each single point along the scanning line. If a
structure remains still, it will produce horizontal lines (since in M-mode our Y-axis
on the screen is depth and X-axis is time). If a structure moves, it will produce a
“granular” pattern (Fig. 4.11 ).
Fig. 4.9 Two ribs with their shadows and amidst them the pleural line: the so-called bat sign
No bat, no exam!
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46
Fig. 4.10 Close-up of the pleural line. Notice the small vertical comet tail artifacts departing from
the bright line
Fig. 4.11 Seashore sign. You may notice the different patterns in M-mode: above the pleural line,
the linear pattern, and the granular pattern below it
A.A. Casamassima and M. Zago
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As you can see in Fig. 4.11 , the chest wall stands still (i.e., makes lines), while
from below the pleural line (the bright line), all we have is granular pattern. With
a bit of imagination, you can describe this image as waves (lines) crashing on the
beach (granular pattern).
Seashore sign (M-mode) is a good method for ruling in/ruling out PTX when you
are a beginner or you are in doubt, because it makes often the diagnosis simpler and
quicker.
When our patient is affected by a PTX, no granular pattern could be detected,
and the seashore becomes the stratosphere sign (all horizontal lines; Figs.
4.12 and
4.13 ). Nothing is moving; horizontal lines are everywhere on the screen.
Sliding Lung: Tips and Tricks
• Amplitude of sliding lung increases from lung apex to basis progressively
• Dyspnea makes the diagnosis diffi cult, even in M-mode, because our
patient is using even his accessory muscles, making our image shake with
every breath
Fig. 4.12 Stratosphere sign. No granular pattern can be identifi ed. The very small intermittent
“granular” pattern columns are related to the movement transmitted to the lung by the beating heart
(“lung pulse”)
4 Thoracic Views: Anatomy, Techniques, Scanning Tips and Tricks, Abnormal Images
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Another important dynamic sign, pathognomonic of PTX, is the “lung point.” It
is pathognomonic for PTX. You can imagine the lung point to be the point in which
the collapsed lung touches the chest wall during breathing cycle. On your US
machine screen, the lung point will appear as an alternation between the presence
and absence of sliding lung (Figs.
4.14 and 4.15 ).
Lung point allows you to defi ne the extent of PTX; from medial to lateral, you
can assess where the lung point is (parasternal, on midclavicular, on anterior axil-
lary, on midaxillary, etc.), precisely evaluating the entity of PTX and relating it to
patient status. Complete PTX has no lung point!
• Pleural line is interrupted by rib shadows. If you’re in trouble, put the
probe on cartilages, next to the sternum: cartilage does not completely
block ultrasound!
• Sliding lung has to be seen in spontaneous and assisted ventilation. It’s
useful to diagnose a wrong endotracheal intubation!
• Apnea cancels the sliding lung (but not small vertical artifacts at the pleural
line – “comet tails”)
Fig. 4.13 A PTX, in both B- and M-modes
A.A. Casamassima and M. Zago
49
Lung point is better observed with the probe along the axis of the intercostal
space, eliminating the rib shadows.
Fig. 4.14 Lung point
Fig. 4.15 Lung point (M-mode): alternation between stratosphere and seashore signs
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Several other static signs were described and cataloged (Lichtenstein) using
alphabet letters. From our practical perspective, just three of them are the most
signifi cant for clinical approach:
1. A-lines
2. B-lines
3. E-lines
A-lines are horizontal reverberation artifacts, repeating themselves below the
pleural line at regular intervals, roughly equal to the distance between the skin and
the pleural line (Figs. 4.16, 4.17, and 4.18 ).
Warning!
• Don’t lose time with US if a tension PTX is suspected (patient is in shock)
• Priority is to decompress the thorax
• If needed, use the probe for a few seconds: rule out hemothorax, confi rm
PTX (parasternal), and insert the needle and drainage
Figs. 4.16, 4.17, and 4.18 A-lines. Notice the bright horizontal lines underneath the pleural line,
at regular intervals
A.A. Casamassima and M. Zago
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Figs. 4.16, 4.17, and 4.18 (continued)
4 Thoracic Views: Anatomy, Techniques, Scanning Tips and Tricks, Abnormal Images