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270 oracic ultrasound
e approach to the patient is comparable to that described in the introductory part of this
text, adapted to the trauma setting and to the patient’s conditions. It should not be redundant.
Very recently, a dynamic and practical viewpoint is entering into the practice of care to
the chest trauma. It is essentially an ECHO-ATLS, in which the priorities dictated by the
acronym ABC are satisfied with the use of ultrasound. In brief, the airway patency or a
correct intubation are proven by bilateral ventilation (bilateral pleural sliding), the absence
of pneumothorax presupposes pleural sliding and the absence of lung points, and a good
ventilation requires a free pleural cavity. Conversely, an improper intubation produces lung
pulse and (later) atelectasis in non-ventilated lung. ese brief instructions, expanded in the
paragraphs on specific pathology, guide the practical implementation of ultrasonography
in chest trauma.
In an algorithmic and ATLS-oriented approach, (i.e. a hot zones approach) the first scans
(A-B) must evaluate the pleural sliding: they are therefore addressed to the left and right
parasternal regions, where there is more accuracy for the diagnosis of pneumothorax. e
second assessment is directed to the pericardial cavity for the search of the haemopericardium.
Subsequent scans will evaluate posterior left and right costophrenic angles. In the supine
patient, this assessment is carried out by placing the probe posteriorly to the patient and
directing it upwards. ese scans are suitable for the diagnosis of hemothorax and belong to
the C stage of the evaluation of the trauma. Suitably, costophrenic assessment can continue
directly with scans for the study of the Morrison pouch and perisplenic regions. So FAST
can immediately follows the thoracic assessment. With this kind of approach, the ultrasound
thoracic assessment does not only extend the FAST, but it precedes (on a pathophysiological
and practical basis) the FAST.
For an accurate study of hemothorax, the subject should ideally be sitting with his arms
above his head. For the study of the heart, his bust should be slightly raised and tilted on
the left side. Naturally, depending on the cases, it may be impossible. erefore, a limit of
ultrasound in thoracic trauma is the impossibility to fully represent all lung surfaces, and
the posterior scans are disadvantaged.
is problem is even worse because of obstacles (clavicles, ribs, sternum and shoulder blades)
covering the surface explored, or when the situation is further complicated by skin lesions,
subcutaneous emphysema, drainage tubes or electrodes.
Particular attention should be paid to the pressure exerted by the probe, which may be painful if exercised on outbreaks of fracture.
e operator must therefore try to circumvent the obstacles or admit to not having obtained
an optimum anatomical representation. In the case of trauma, this is of particular importance
since the alteration is often focal.
Beyond these obvious limitations, chest ultrasound has a great diagnostic power in trauma
patients with hemo- and pneumothorax, which are usually located in predictable intrathoracic positions (hot zones).
A further advantage is related to the ease of approach of the ultrasound machine, especially
nowadays that the devices are significantly miniaturized.
For a trained operator, performing a complete scan of the chest, or extended FAST, takes
no more than three minutes.
oracic trauma 271
➣ Intubation
17-20
A proper intubation is a prerequisite for effective controlled ventilation. e correct position
of the endotracheal tube should be defined immediately after intubation, and the means used
are different. It is necessary to ensure that the chest wall expands or that breath sounds are
heard on both lung fields. Alternatively a detector of end tidal CO2 can be used or the tube
can be visualized by means of a chest X-ray. e latter option is clearly laborious in a context
of resuscitation or severe illness of the patient.
Ultrasonography has been proposed as a means for verifying the proper placement of the
endotracheal tube for its ability to define the pleural sliding. e normally ventilating or
properly intubated subject shows a bilateral sliding.
An accidental or intentional intubation of a main bronchus makes a lung non-ventilating and
it abolishes the sliding on the side excluded. e pleural pulse then replaces the pleural sliding
on this side. e exclusion from the ventilation of a lung or lobe, after a few minutes causes
a progressive resorption of the intraalveolar and intrabronchial air. is leads to detectable
degrees of atelectasis after about twenty minutes.
e repositioning of the endotracheal tube allows air to re-fill the airways and the excluded
lobular units, thus solving any atelectasis and reactivating a normal sliding of the pleura.
➣ Pneumothorax
Sonographic diagnosis of traumatic pneumothorax is similar to the diagnosis of PNX with
other etiologies. erefore, many data have already been reported in the chapter on spontaneous pneumothorax (Chapter 6).
PNX is present in up to 25% of all closed chest traumas21. e accumulation of air in the
pleural cavity from outside (open pneumothorax) or from inside, causes a more or less marked
collapse of the lung with a disorder of the respiratory mechanics or, in the case of cardiomediastinal shift (hypertensive PNX), with hemodynamic alterations.
Chest findings are well known (dyspnea, thoracic hyper resonance, reduced breath sounds,
venous hypertension), so that in critical cases it may necessary not to wait for instrumental
investigations, but to proceed immediately to tube thoracostomy. However, the clinical suspicion of PNX is not confirmed in 20-30% of cases.
e instrumental demonstration of PNX is usually based on chest X-ray that in emergency
is performed with a mobile device using only anteroposterior scan. Under these conditions,
the sensitivity of radiography, especially for low volumes of lung collapse, can drop to values
of 50%22. ese undiagnosed pneumothorax are the so-called occult pneumothorax23. eir
demonstration was possible by the use of CT in the secondary instrumental evaluation of
abdominal trauma. In its high scans, even through the lung bases, CT shows anterior or
anterolateral air collections, extended to a few centimeters, unsuspected by chest X-ray
(Figs. 2-4)
cm thick and extended for no more than 4 cm; anterior, if more than 1 cm thick but not
extended beyond the middle coronal thoracic line (midaxillary line); anterolateral, if extended
beyond this line. is classification has some therapeutic implication.
ere is evidence that minimal PNX can be treated conservatively. e anterior ones can be
monitored clinically, provided that they do not involve subjects that have to undergo ventilation, in which case it may be prudent to put a pleural tube in place.
24-25
. Occult PNX were classified by Wolfman26 as: minimal, if not more than 1
272 oracic ultrasound
Figure 2 – Occult PNX: intrapleural air is
evident on CT (B), but the diagnosis of PNX can
escape the X-ray performed in the emergency
department (A).
Figure 4 – Occult PNX: severe closed trauma of the chest. To the left: X-ray performed in the emergency
department has low quality and gives very little information. A CT scan performed a few minutes later
(right) shows a moderate right hemopneumothorax and pulmonary contusions. The X-ray in the supine
patient may not show significant density changes, in the case of coexistence in the same hemithorax of
declive fluid and antideclive air.
Figure 3 – Occult PNX. A: X-ray performed
at admission, patient with closed trauma in left
hemithorax, false negative. B: X-ray performed
the following day in Radiology with patient in the
upright position. Evident left PNX.
oracic trauma 273
Drainage would instead be always appropriate for anterolateral PNX. Overall, about 20%
of occult PNX requires treatment. Recently27 it has been observed that, among patients with
occult pneumothorax by closed chest trauma, the simple clinical observation was possible in
79% of cases, with 6% of patients who subsequently required drainage. Among the subjects
undergoing ventilation with positive pressure, 14% of patients required tube thoracostomy.
e clinical significance of occult pneumothorax has always been uncertain, although it has
been recognized that even small PNX in humans undergoing mechanical ventilation, could
have significant aggravations28. is consideration gave rise to the need to quantify the volume of each PNX, in order to identify those at greater risk. In these cases the CT’s role is
irreplaceable29, being able to demonstrate both the lateral extension of the collected air, and
its thickness. Although this “malignancy” of small PNX has been called into question30, we
believe that it is necessary to be cautious, and in this context, echography can be a useful
monitoring tool. In fact, even if ultrasound may not estimate the thickness of the intrathoracic
collection, examination of lung points makes its lateral extension evident. Repeated detections can show both the reduction of the extension of the PNX after thoracostomy, both its
spontaneous aggravation or an enlargement induced by mechanical ventilation (Figs. 5-6).
Figure 5 – In non-massive PNX, the air collected in the supine patient outlines a parasternal region,
in which ultrasound will only show static artifacts. At the point where the lung sticks to the wall,
generally more laterally, a pleural mobile line becomes evident. This point is called “lung point” and its
representation is shown on the right. On the left, the CT image with lung point (arrow).
e use of ultrasound for the definition of PNX appeared in the early eighties, when Rantanen31
was able to diagnose pneumothorax in horses, demonstrating the absence of visceral pleural
movement.
e subsequent experiences on humans
correlated positively with the presence of air in the pleural cavity
To summarize what has already been described
31-37
have shown that the absence of this movement
43-47
in Chapter 6, in a patient in whom the
38-42
(Fig. 7).
“sliding sign” cannot be demonstrated or is uncertain in a particular area:
• e presence of even a single, real, lung point has a positive, almost total predictive power
for PNX;
• e presence of even a single, unambiguous, B Line has a negative, almost total predictive
power for PNX.
274 oracic ultrasound
Figures 8, 9, 10 illustrate these principles, while Figure 11 shows how to scan the chest for
the search of PNX in the supine patient. In the vast majority of cases the intrathoracic air
collection assumes a sloping position and is easily explored by the probe located in the deep
sulcus area, represented by the paracardiac regions and the anterior costophrenic angles.
In the case of trauma, when pain limits the respiratory excursions, sometimes it is difficult
to see the pleural sliding with the convex probe. Failure to visualize unequivocal lung points
can make the diagnosis uncertain.
In these cases it is useful to perform a sensitized pleural ultrasound, obtained using a linear
probe at 6-7 MHz, setting the device with a very low gain (to get the echogenicity only at
the level of the pleural line) and operating without tissue harmonics.
With this method, the pleural dynamics is seen better.
Figure 6 – PNX. A lung point (arrow) at the level of the chest hemicoronal line (black line). An air
collection extended beyond this line identifies the anterolateral pneumothoraces, usually visible on the
X-ray performed with the patient in the supine position.
Wall
Lung
Figure 7 – M-Mode representation document PNX even in a static image. The absence of
pleuropulmonary movement in PNX is highlighted by the absolute fixity of the lines (left).
oracic trauma 275
Pleural line
Figure 8 – A: static image of PNX. B: image obtained at the same level and in the same subject after
drainage of pneumothorax. When the lung is in contact with the wall, subtle differences are evident.
Note the slightly thicker pleural line, less evident A Lines and the more echogenic lung background.
B Lines
Figure 9 – Both physiological and pathological B Lines, allow to identify more easily the sliding sign
thanks to their movement, and they exclude PNX at that level.
Figure 10 – The demonstration of a parenchymal consolidation (A) or of an interstitial syndrome (B)
excludes the presence of PNX at that level (pulmonary contusions after drainage of PNX).
276 oracic ultrasound
Figure 11 – A pneumothorax in the supine patient is analyzed starting from the paracardiac regions
(deep sulcus area), where the air, tends to collect. Subsequently, by means of linear longitudinal scans,
the research should be extended in the front (1) and to the side (2).
Sometimes the presence of pleural adhesions creates PNX located in unusual positions; it is
therefore necessary to perform extensive scans very carefully, and if possible, with deep breaths.
Even in these cases, it is useful to apply the method of sensitization indicated just above.
SUPINE
Figure 12 – Hemopneumothorax. Top: X-ray shows a right pleural effusion. In particular, the figure on
the right shows a hydroaeric image at the level of the right lateral costophrenic angle. The ultrasound
scans (bottom) show a clear effusion. Right (large arrow): air artifacts in retroparietal position on the
pleural fluid. The small arrow indicates the pleural plane of the lung in the fluid. The air acts as a false
pleural plane.
oracic trauma 277
Other sonographic signs of PNX exist, but they occur with low frequency or in particular
circumstances: the disappearance of an underlying lesion, first visible, the cancellation, from
the air (which floats on the liquid) of a pleural effusion during respiration, or the presence
of air microbubbles in the context of a hemothorax (Fig. 12).
e identification of small left anterior pneumothorax is particularly delicate. Lungs normally expand with breaths on the acoustic window of the heart, obscuring it (Clips 1-2). In
case of PNX this “curtain-like” movement is absent and the cardiac window can disappear.
Sometimes it is replaced by momentary contacts of the heart against the chest wall caused
by the systole, generating short and rhythmic “heart points”.
Given its high values of sensitivity and specificity already discussed in Chapter 6, ultrasonography must enter into the early survey protocols for detecting PTX in trauma patients as an
extension of FAST (E-FAST), particularly targeted to the definition of occult pneumothorax48. Ultrasonography is typically an emergency or bedside examination, with a much better
accuracy than the simple physical examination and the technically imperfect radiography.
Considering that CT is the gold standard for this disease, it is easy to conclude that in the work
up of a chest injured patient, traditional X-ray does not currently have a coherent position.
e technique to be used for the ultrasound of pneumothorax has been described in the
general part concerning this pathology. According to ABC priorities, ultrasonography of
deep sulcus areas has priority over the research of cavitary (pleural or peritoneal) effusions,
which are relevant to C.
is method is very promising even in unusual contexts, such as on the scene of the trauma, in
the case of war events, during transportation of victims or in extreme environments (isolated
places, mountains or during space travel).
Clip 1 – Anterior PNX: presence of lung point and darkening of the cardiac
acoustic window by the PNX.
Clip 2 – Minimal anterior PNX. Two lung points with an area where no
pleural sliding is observed, due to a small PNX.
➣ Hemothorax
Blood in the pleural cavity is detected in at least 50% of chest traumas49. Hemorrhage origins
from the pulmonary parenchyma, the chest wall with its internal intercostal and mammary
arteries or from the heart and the mediastinal vessels. Hemothorax is present in the case of
lesions of abdominal organs (liver and spleen), in combination with diaphragm rupture.
At least 1000 ml of blood in the pleural cavity defines a massive hemothorax often associated
with hemodynamic instability50. 200-300 ml of blood in the pleural cavity in stable patients
can be revealed by a well performed chest X-ray, but minor bleedings can be hidden to X-ray,
if the patient is in the supine or upright position.
278 oracic ultrasound
In the supine position, blood tends to locate in the costovertebral recesses and it determines a
diffuse opacity in a hemithorax that it is difficult to estimate, even if it is 1 liter in quantity50.
e definitive diagnosis is therefore possible after the execution of CT scans. CT is a very
accurate examination in chest traumatology, because the blood determines typical attenuation values (35-70 HU), but it can be too sensitive in identifying injuries with low clinical
significance51.
In the presence of hemothorax and in the absence of serous synechiae, transonic images of
free fluid are produced. e blood collects in the sloping areas of the pleural cavities and is
easily detected by the ultrasound beam
52,53
.
e general principles for the recognition of pleural effusions have been described in the
section on pleural diseases (Chapter 5).
Blood
Atelectasis
Figure 13 – Hemothorax in a patient with blunt trauma and left rib fractures. The effusion appears as
a transonic area. Note the atelectatic pulmonary base.
Figure 14 – Hemothorax: the pleural fluid is corpusculated.
Fresh blood may appear devoid of echoes in suspension, as opposed to the material that has
remained in place for more or less long time and which can therefore appear corpuscular, with
oracic trauma 279
fibrin branches or weakly echogenic clots. Often, even in the acute stages, it is corpusculated
(echogenic) (Figs. 13-14).
Sometimes the fibrin is deposited on the visceral pleura or on the diaphragm, making them
irregular and thickened. e fluid is an excellent acoustic window to the underlying parenchyma, which appears mobile in the liquid and has a characteristic feature, related to the
compression of the tissue (Clip 3).
Clip 3 – Massive left hemothorax: the pleural fluid is corpusculated. Note
the complete atelectasis of the left lung. An acoustic window allows the
visualization of the thoracic aorta.
A moderately compressed lung shows B Lines and/or white lung artifacts. A greater compression results in a semisolid or solid appearance with or without air artifacts. e presence of
parenchymal changes is, in these circumstances, facilitated.
Except for the presence of adhesions, in a sitting, semi-sitting or standing position, the liquid
tends to collect on the diaphragm, raising the lung base. It therefore generates a height between
the diaphragm and the base defined “water level”, which correlates with the effusion volume.
On the contrary, laterally the liquid goes up to the armpit and gets thinner (Damoiseau-Ellis
line), generating a lateral meniscus or sneaking in the fissures, that become visible (Fig. 15).
An approximate estimate of the hemothorax volume can be expressed according to the formula
which multiplies the constant value of 70 and the sum of the retroparietal and subpulmonary
height of the effusion.
Hemothorax
Figure 15 – Perfect evidence of the pleura and a fissure, highlighted by the presence of a retroparietal
hemothorax.
For this assessment, the patient is scanned in the sitting or upright position, by sliding the
probe from top to bottom, along the thoracic lines, in particular by performing posterolateral
longitudinal scans above the diaphragm. Even in the supine position, with slightly raised
hemithorax, the image of a posterior effusion becomes clear when the probe is oriented upward.
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