Walif Chbeir: Medical Imaging of PneumoThorax (PNO)–3

Edited March02,2016
Update sept 30, 2016
Medical Imaging of PneumoThorax (PNO3)
Dr WALIF CHBEIR
C- UltraSound
1- Introduction:
* Lung sonography has rapidly emerged as a reliable technique in the evaluation of various
thoracic diseases. One important, well established application is the diagnosis of a
pneumothorax.
* Ultrasound has a higher sensitivity than the traditional upright anteroposterior chest
radiography (CXR) for the detection of a pneumothorax. (Sonographic diagnosis of pneumothorax)
- Small occult pneumothoraces may be missed on CXR during a busy trauma scenario, and
CXR may not always be feasible in critically ill patients.
- In certain studies, the sensivity of US has been similar to that found in CT scan.
* Initial Ultrasonographic evaluation of the chest in the critically ill patient (Focus On: Ultrasound
Detection of Traumatic Anterior Pneumothorax.) demonstrated the superiority of bedside ultrasound in the
detection of anterior pneumothoraces, compared with supine chest radiographs (CXR).
- Recent data from acutely injured patients support the initial studies by demonstrating that
bedside ultrasound is more sensitive than chest radiography in the detection of an anterior
pneumothorax when computed tomography (CT) is used as the gold standard. (Focus On: Ultrasound
Detection of Traumatic Anterior Pneumothorax).
* Computed tomography, the gold standard for the detection of pneumothorax, requires
patients to be transported out of the clinical area, compromising their hemodynamic stability
and delaying the diagnosis.
* As ultrasound machines have become more portable and easier to use, lung sonography now
allows a rapid evaluation of an unstable patient, at the bedside. These advantages combined

with the low cost and ease of use, have allowed thoracic sonography to become a useful
modality in many clinical settings.
* The Focused Assessment with Sonography in Trauma (FAST) examination has now been
modified to include lung imaging as part of the evaluation in a trauma patient. The application
has been renamed as the EFAST examination, with ‘E’ standing for extended, including the
standard lung views.
* The diagnosis of a pneumothorax is usually made with a combination of clinical signs and
symptoms, which may be subtle, and plain chest radiography.
-- Regardless of its presentation, the early detection and treatment of a pneumothorax is
critical.
-- Small( 10% or less) or medium (11 to 40%) sized pneumothoraces are generally not
lifethreatening and their management varies.
- However, a delay in the diagnosis and treatment, especially in those who are mechanically
ventilated, may lead to the progression of a pneumothorax and resultant hemodynamic
instability. In these critical situations where a subtle pneumothorax may be missed, a quick
bedside lung ultrasound may expedite the diagnosis, treatment, and resuscitation of a patient
who may have otherwise decompensated.
* These findings underline the utility of performing a rapid bedside ultrasound, in emergent
traumatic setting, to possibly aid in the diagnosis, prior to sending a patient for a CT scan.
2-Probe selection and equipment
- The bedside sonographic diagnosis of pneumothorax can be performed with most ultrasound
machines, which is especially helpful in the critically ill and hemodynamically unstable patient,
as it obviates the need for transport.
- A straight linear array high frequency probe (5–13 MHz) may be most helpful in analyzing
superficial structures such as the pleural line and providing better resolution.
- A microconvex or curvilinear array probe may be more suitable for deeper lung imaging as it
provides better penetration (1–8 MHz), at the cost of less resolution.
- Finally, some advocate the use of the phased array probe, generally used in cardiac imaging
(2–8 MHz), as its flat and smaller footprint is better suited for imaging in between the ribs.
3- Technique and normal anatomy

*
- A pneumothorax contains air and no fluid, and therefore, will rise to the least dependent area
of the chest. In a supine patient this area corresponds to the anterior region of the chest at
approximately the second to fourth intercostal spaces in the midclavicular line. So, this
location will identify the majority of significant pneumothoraces in the supine patient.
- In contrast, air will accumulate in an apicolateral location in an upright patient.
- Based on the above, patients are scanned in a supine or near to supine position. The probe
should be placed in a sagittal position (indicator pointing cephalad) on the most anterior region
of the chest (usually around the nipple line/4th-5th rib space). In general, scanning of 2 - 3
intercostal spaces in the midclavicular line is recommended.
See fig2, in Sonographic diagnosis of pneumothorax, in J Emerg Trauma Shock. 2012
Jan-Mar; 5(1): 76–81, in PMC free articles, PMCID: PMC3299161, Received 2011 Jun 1;
Accepted 2011 Jun 6, (Page consulted February 12, 2016).
All right reserved.
Go to http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F1/
- The sonographer should first identify the landmarks of two ribs with posterior shadowing
behind them and visualize the pleural line in between them. This is typically called ‘the bat
sign’ where the periosteum of the ribs represents the wings and the bright hyperechoic pleural
line in between them represents the bats’ body.
See Fig 2 in Sonographic diagnosis of pneumothorax, in J Emerg Trauma Shock. 2012
All right reserved.
- If the ribs are not visualized the probe should be slowly moved in a caudal direction
(inferiorly) until two ribs appear on the screen. It is in between these two rib landmarks that the
two layers of pleura, parietal and visceral, are seen sliding across one another. As stated earlier,

air will rise to the anterior chest wall, and therefore a pneumothorax that is large enough to
require a chest tube will appear with this simple technique.
* The presence of pleural sliding is the most important finding in normal aerated lung. Lung
sliding corresponds to the to and fro movement of the visceral pleura on the parietal pleura that
occurs with respiration. It is a dynamic sign and can be identified on ultrasound as horizontal
movement along the pleural line. Sliding is best seen at the lung apex in a supine patient.
.The most important point to remember with lung sliding is that its signs arise at and below
the pleural line and never above (vital to misinterpreting muscular sliding in dyspnoea and
subcutaneous emphysema). If there is subcutaneous emphysema it can usually be moved out of
the way with pressure from the probe.
* The use of M mode, which detects motion over time, provides more evidence that the
pleural line is sliding. It is beneficial in patients where sliding may be subtle, such as, in the
elderly or in patients with poor pulmonary reserve, who are not taking large breaths. The M
mode cursor is placed over the pleural line and two different patterns are displayed on the
screen: The motionless portion of the chest above the pleural line creates horizontal ‘waves,’
and the sliding below the pleural line creates a granular pattern, the ‘sand’. The resultant
picture is one that resembles waves crashing in onto the sand and is therefore called the
‘seashore sign’ and is present in normal lung.
See Fig 3 in Sonographic diagnosis of pneumothorax, in J Emerg Trauma Shock. 2012
All right reserved.
* ‘B lines’ or ‘comet tail artifacts’ are reverberation artifacts that appear as hyperechoic
vertical lines that extend from the bright white hyperechoic pleural line to the edge of the screen
without fading. ‘Comettail artifacts’ move synchronously with lung or pleural sliding and
respiratory movements., in a normal well-aerated lung.
- These artifacts are seen in normal lung due to the acoustic impedance differences between
water and air.

- A few visualized ‘B lines’ in dependent regions are expected in normal aerated lung and are
visualized moving along with the sliding pleura.
- Excessive ‘B lines’, especially in the anterior lung, are abnormal and are usually indicative
of interstitial edema.
See Fig 4 in Sonographic diagnosis of pneumothorax, in J Emerg Trauma Shock.
2012 Jan-Mar; 5(1): 76–81, in PMC free articles, PMCID: PMC3299161, Received 2011 Jun
1; Accepted 2011 Jun 6, (Page consulted February 12, 2016).
All right reserved.
* The average time to perform this examination varies from two to three minutes; less than one
minute to rule out a pneumothorax and several minutes to rule it in.
4-Sonographic signs of pneumothorax
1-Absence of lung sliding:
* In a pneumothorax, there is air present that separates the visceral and parietal pleura and
prevents visualization of the visceral pleura. In this situation, lung sliding is absent. This lack of
lung sliding can be visualized by identifying the landmarks discussed earlier. Two ribs should
be identified with the pleural line in between them. The typical to and fro movement or
shimmering of the pleural line will not be present.
* The same technique using M mode can be used to confirm a lack of sliding. The resultant M
mode tracing in a pneumothorax will only display one pattern of parallel horizontal lines above
and below the pleural line, exemplifying the lack of movement. This pattern resembles a
‘barcode’ and is often called the ‘stratosphere sign’.
All right reserved.

* The negative predictive value for lung sliding is reported as 99.2–100%, indicating that the
presence of sliding effectively rules out a pneumothorax.
- However, the absence of lung sliding does not necessarily indicate that a pneumothorax is
present. Lung sliding is abolished in a variety of conditions other than pneumothorax, including
acute respiratory distress syndrome (ARDS), pulmonary fibrosis, large consolidations, pleural
adhesions, atelectasis, right mainstem intubation, and phrenic nerve paralysis.
* Specificity values range from 60–99% depending on the patient population, with higher
values in the general population and lower values in the Intensive Care Unit and in those with
ARDS.
- Although the absence of lung sliding is not specific for pneumothorax, the combination of
this with other signs improves the accuracy of the diagnosis.
2- loss of Comet tail artifacts or ‘B lines’
* Ultrasound demonstrates the loss of ‘comettail artifacts’ in patients with a pneumothorax.
These reverberation artifacts are lost due to air accumulating within the pleural space.
* The negative predictive value for this artifact is high, reported at 98–100%, such that
visualization of even one comettail essentially rules out the diagnosis of a pneumothorax.
3- A lines are other important thoracic artifacts that can help in the diagnosis of a
pneumothorax.
- These are also reverberation artifacts appearing as equally spaced repetitive horizontal
hyperechoic lines reflecting off of the pleura. The space in between each A line
corresponds to the same distance between the skin surface and the parietal pleura.
All right reserved.

- In the normal patient, when ‘B lines’ are present, they extend from the pleural line and
erase ‘A lines’, as they emanate out to the edge of the screen.
- ‘A lines’ will be present in a patient with a pneumothorax, but ‘B lines’ will not.
- If lung sliding is absent with the presence of ‘A lines’, the sensitivity and specificity for an
occult pneumothorax is as high as 95 and 94%, respectively.
4- Lung- point sign
* The ‘lung- point sign’ occurs at the border of a pneumothorax. It is due to sliding lung
intermittently coming into contact with the chest wall during inspiration and is helpful in
determining the actual size of the pneumothorax.
* This sign can further be delineated using M mode where alternating ‘seashore’ and
‘stratosphere’ patterns are depicted over time.
All right reserved.
* The ‘lung point sign’ is 100% specific for pneumothorax and defines its border. The location
of the lung point is beneficial in determining the size of the pneumothorax.
* If a lack of lung sliding is visualized anteriorly, the probe can progressively be moved to more
lateral and posterior positions on the chest wall searching for the location of the lung-point. The
more lateral or posterior the ‘lung-point sign’ is identified, the larger the pneumothorax.
* Therefore, if the ‘lungpoint sign’ is seen in an anterior location on the chest wall, the
sonographer can be assured that the pneumothorax is relatively small. Although the
specificity is high, the sensitivity of the ‘lung-point sign’ is relatively low (reported at 66%) and
is not seen in cases of total lung collapse.
* Studies have shown concordance between pneumothorax size on ultrasound and CT scan,
reportedly within 1.9–2.3 cm (ref. 28 in Sonographic diagnostic of PNO).

* The determination of the size of a pneumothorax is important for clinical decision making,
as larger pneumothoraces are more likely to require thoracostomy.
5-Other signs
* The ‘Power Slide’ refers to the use of power (angiography) Doppler to help identify lung
sliding.
- Power Doppler is very sensitive and picks up subtle flow and movement.
- If there is lung sliding present, power Doppler will light up the sliding pleural line with color
flow.
All right reserved.
- This technique can be helpful in cases of subtle sliding when direct visualization may be
difficult.
- The disadvantage of this type of Doppler is that due to its increased sensitivity, the probe
needs to be held in a steady manner and the patient has to be motionless in order to
prevent artifact and erroneous color flow over the pleural line, when sliding is actually absent.
* The ‘lung pulse’ refers to the rhythmic movement of the pleura in synchrony with the
cardiac rhythm. It is best viewed in areas of the lung adjacent to the heart, at the pleural line.
These movements form a T (T Line) with the pleural line on Mmode.
- The ‘lung pulse’ is a result of cardiac vibrations being transmitted to the lung pleura in poorly
aerated lung. Cardiac activity is essentially detected at the pleural line when there is absent
lung sliding.
- In normal well aerated lung, the ‘lung pulse’ is not present.
- As transmission through lung is required they rule out a pneumothorax.

5- Limitations
* Lack of lung sliding and comet tail artifacts may not always indicate a pneumothorax.
Recently intubated patients may have a mainstem bronchus intubation preventing adequate
aeration of one lung and not demonstrate either lung sliding or comet tail artifacts, giving the
operator a false impression of pneumothorax.
* Causes of Reduced sliding
- Low tidal volume (ventilator settings, abdominal compartment syndrome, acute asthma
etc)
-ARDS.
* Causes of Abolished sliding:
Pneumothorax / Severe consolidation / ARDS / Atelectasis/ Pneumonectomy.
Pneumonia and ARDS abolish sliding by adherences secondary to inflammation (exudative
process) otherwise known as pleural symphysis. Both will usually show B lines allowing the
ruling out of pneumothorax.
* Bullae: Even with large bullae the 2 pleural layers are still opposed so sliding will still be
observed. Therefore bullae should not causes false positives for pneumothorax.
* If a pneumothorax is septated there may be some septa still attached to the parietal pleura
giving rise to B lines at these points. This is more likely to be observed in cases of recurrent
pneumathoraces. There will be no sliding and the lung point will still be visible.
* Occasionally pneumothoraces may not be anterior for example where there are lung
contusions stopping the free movement of air against gravity. This is more commonly seen in
children. They will be visible in the axillae.
* Also, when evaluating the paracardiac regions on the left chest, care must be taken to
identify the pleural line. The heart rises and falls with the movement of the diaphragm, and this
motion may be misinterpreted as a "lung point," especially if the probe marker is pointed
caudad instead of cephalad (as recommended).
6- Management
* A small anterior pneumothorax will usually not need draining even in mechanical
ventilation. They can resolve spontaneously.

- It should be regularly assessed however as it can evolve. Check the lung point is not moving
laterally. Lung protective ventilation will lessen the chances of a pneumothorax increasing in
size. A lateral lung point suggests a drain will be required.
- Repeat CXRs are not required. US is better for monitoring a pneumothorax.
* US should be routine after procedures which may cause a pneumothorax (central line
insertion, thoracocentesis).
* Mapping the location of a pneumothorax means that traditional insertion sites for drains do
not need to be used. Drains should be inserted away from the lung point.
* US should be used to demonstrate that the lung had expanded following drainage. It can
then also be used to show that the lung remains expanded (the leak has sealed) following
clamping a drain thus allowing confident removal before again repeating US to confirm no
reaccumulation of air post removal.
* In stable trauma patients with ultrasonographic signs of a pneumothorax and a negative
supine chest radiograph, we recommend a repeat upright plain film after clearance of cervical
immobilization for confirmation of an occult pneumothorax.
- In patients where cervical immobilization cannot be removed, we recommend computed
tomography of the chest to delineate the pneumothorax early in trauma care (before
transportation or intubation).
* Lung-ultrasonography can prove an alternative diagnostic procedure in the difficult
diagnosis of pneumothorax in critically ill patients with severe ARDS, which not only permits
bedside assessment of lung pathology but also assists in the evaluation of mechanical
ventilation parameters, as well as the evaluation of lung overdistension and PEEP-induced lung
recruitment (ARDS et PNO; Journal of Thoracic Disease).
* Recently, US has been used to assist in the placement of chest tubes, and in aspiration of
loculated pneumothorax. (Ultrasound-assisted aspiration of loculated pneumothorax: A new technique) .
7- CONCLUSIONS
* Thoracic sonography for the detection of pneumothorax has become a well established
modality in the acute care setting. It is indispensible in the blunt or penetrating chest trauma
patient, where the identification of a pneumothorax can prevent lifethreatening consequences.

* The traditional upright AP radiograph has become less important due to its poor sensitivity
in diagnosing a pneumothorax compared to ultrasound.
* Although CT scan remains the gold standard and may still catch smaller occult
pneumothoraces that ultrasound misses, its disadvantages are becoming more apparent.
* Bedside ultrasound obviates the need for patient transport in unstable situations, it eliminates
radiation exposure, it is quicker to perform and is immediately interpreted at the bedside
without unnecessary delays. In addition, it is more costeffective and can be repeated multiple
times during a resuscitation.
- In addition, ultrasound is the perfect modality in the emergency and critical care setting after
performing certain procedures, such as a thoracentesis or the placement of a central line, to
quickly confirm the presence of lung sliding and to rule out an iatrogenic pneumothorax.
- It has also been found to be beneficial in the postintubation scenario, where a confirmation of
bilateral lung sliding rules out a right mainstem intubation.
- The increasing portability of newer ultrasound machines makes them easier to use in first
responder and disaster settings, wilderness medicine, air medical transport, rural medicine, and
even space explorations.
- Studies indicate that the recognition of key artifacts in thoracic ultrasound is readily teachable
to both physicians as well as nonphysician health care providers and its uses continue to expand
in the out of hospital setting.
8- Vidéos
1-
lung-point-sign-of-pneumothorax-on-ultrasound.mp4
Case courtesy of Dr Andrew Dixon, <a href="https://radiopaedia.org/">Radiopaedia.org</a>. From the case <a
href="https://radiopaedia.org/cases/45149">rID: 45149</a>
Or go to
https://radiopaedia.org/articles/pneumothorax-ultrasound
2-Ultrasound Lung Scanning Tutorial with Dr. Shane Arishenkoff - Clarius
https://www.youtube.com/watch?v=jh7EP7jiW98

3- URL Link:
https://www.youtube.com/results?search_query=pneumothorax+ultrasound

Walif Chbeir: Medical Imaging of PneumoThorax (PNO)–3

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Walif Chbeir: Medical Imaging of PneumoThorax (PNO)–3