The pleura is visualized under the intercostal muscles and subcutaneous tissue. Ribs obscure its view but serve as a convenient marker for image acquisition. If you can see a pleural line even below what you think is a rib, then this is probably cartilage. Cartilage transduces more ultrasound waves than ribs, allowing us to differentiate between ribs and cartilage.

Parietal and visceral pleura

Hansel J, Privsek M edts. (2016) PACE:POCUS Assisted Clinical Examination - a modular curriculum.

INTERCOSTAL SPACE (“BAT SIGN”)

When we are performing lung ultrasound, we need to find the proper position of the probe so that we will be able to find different artifacts and signs. The ultrasound probe is placed longitudinally on a patient’s chest. The long axis of the probe is parallel to the sagittal plane of the body. You should position it in the way that you cross two ribs. If your position of the probe is correct, you will be able to see a bat sign on the ultrasound screen.

When you manage to find and show the bat sign, you must be aware that what you see as bat wings is the acoustic shadow of the ribs. Ribs are bones, and bones have a much higher acoustic impedance than other tissues that cover them. Almost all ultrasound waves are reflected, and no ultrasound wave comes through, resulting in a shadow (black bat wings) you see behind the ribs. You can see a hyperechoic line between the two ribs, the so-called pleural line that resembles a bat’s head or back. It is hyperechoic because it represents the interface between the soft tissue and lung parenchyma, which has a different acoustic impedance than the covering tissue (mostly muscle and skin) and thus reflects ultrasound waves.

"Bat sign"

Available at:https://ai2-s2-public.s3.amazonaws.com/figures/2017-08-08/836d74628151ea0a5e7bb7ae153204bdba954462/18-Figure2-1.png (Accessed: 13 November 2019)

Probe position when evaluating pleural sliding PAME Maribor
Probe position when evaluating pleural sliding PAME Maribor
Intercostal space anatomy PAME Maribor

PLEURAL SLIDING (“SEASHORE” and “BARCODE SIGN”)

The lungs are enveloped by two membranous structures called visceral and parietal pleura. The visceral pleura covers the lungs tightly while the parietal pleura envelopes the visceral one and is in contact with the thoracic wall. Between both pleurae, there is a thin virtual space, which normally contains a few milliliters of fluid to lubricate the pleural space and offers minimal traction when breathing.

The diaphragm contracts and moves towards the abdomen when we breathe in. The muscles in the thoracic wall contract and expand the thorax, causing the volume of the thoracic cavity to increase. The pressure in the lungs decreases, and the air is sucked into the lungs, expanding the lungs. When we breathe in, the lungs and visceral pleura slide down at the same time as the parietal pleura, which is attached to the wall of the thorax. The opposite happens when we breathe out.

Figure 4

Pleural sliding PAME Maribor

If we examine the healthy lungs with ultrasound and find the pleural line, we can see how the visceral pleura slides at the same time as the parietal pleura when breathing. We cannot distinguish between the parietal and visceral pleura with ultrasound because they are close together. We can see the pleural sliding as “ants climbing the tree,” “beads on a string,” or “moving curtains”. The so-called lung sliding is seen as little spikes that move with each breath. Using B mode the so-called lung sliding is seen as little spikes that move with each breat. Using M mode, one-dimensional view, which shows the moving of the structures in time we can see the so-called “seashore sign”. The upper portion, which represents waves coming towards the shore, is the skin, subcutaneous tissue, and muscles in the thoracic wall. The lower part, which looks like sand on the shore, represents the lungs. The border between water (in reality, soft tissue) and sand (in reality, air-filled lungs) is the pleural line.

"Seashore sign"

Available at: https://openi.nlm.nih.gov/imgs/512/103/3522086/PMC3522086_CPR-8-217_F3.png?keywords=condition,pneumothorax (Accessed: 13 november 2019)

Normally, there is no air in the pleural space. If air somehow enters the space between the parietal and visceral pleura, we call this condition pneumothorax. When there is air in the pleural space, the two leaves of pleura are not tightly connected anymore. Consequently, we cannot observe the pleural sliding with the ultrasound. Instead, we can observe the lack of sliding in both 2D and M-mode, where we see the special sign, which is called the “barcode” or “stratospheresign. There are many horizontal hyperechoic lines. They are produced when there is air in the pleural space. The air causes the reflection of ultrasound waves from the parietal pleura. Lines above and below the now static pleural line arise from the mechanism that is similar to the appearance of A-lines.

Lung sliding is an extremely sensitive indicator of normal lung movement and function. Absence, therefore, should raise a concern, and further investigations for other signs and symptoms should be conducted.

"Barcode (stratosphere) sign"

Available at: https://www.researchgate.net/profile/Zhongheng_Zhang/publication/282608993/figure/fig1/AS:391753795424258@1470412791214/Barcode-or-stratosphere-sign-typically-found-in-patients-with-pneumothorax-In-the.png (Accessed: 13 November 2019)

Pneumothorax

Pneumothorax is defined as the presence of air or gas in the pleural cavity, which can impair oxygenation and/or ventilation. The causes of pneumothorax are different, but it occurs when air leaks into the space between the lungs and chest wall. The air then pushes on the outside of the lungs and makes them collapse. The collapse can affect a complete lung, or it can be restricted to only a portion of the lung. Pneumothorax can be divided into two broad groups: traumatic or atraumatic (spontaneous).

Atraumatic can be further divided into primary or secondary. It can be caused by a chest injury, lung diseases, or even mechanical ventilation. A spontaneous pneumothorax occurs without a history of trauma. It is further classified as primary (young, fit, and healthy persons without a known lung disease) or secondary (a complication of the underlying lung pathology: COPD, cystic fibrosis, etc.).

By patophysiological mechanism pneumothorax can also be classified as closed (air enters through a hole in the lung), open (air enters through a lesion in the chest wall, e.g., following penetrating trauma), or as tension pneumothorax (air enters the pleural space on inspiration but cannot exit. This can lead to the collapse and compression of the thoracic organs and tissues).

It can be a life-threatening condition and requires immediate intervention by decompression.

Signs and symptoms of pneumothorax:

  • sharp chest pain, made worse by a deep breath or cough;
  • shortness of breath;
  • nasal flaring;
  • hypotension;
  • tachycardia or cyanosis.

Typical examination findings include reduced or absent breath sounds on auscultation, reduced ipsilateral chest expansion, and hyper-resonant percussion. Hemodynamic compromise (hypotension or cardiac arrest), or significant hypoxia is unusual in primary pneumothorax. It is more common and life-threatening in tension pneumothorax also because of mediastinal shift (tracheal deviation and jugular venous distention) and reduced venous return to the heart leading to cardiovascular collapse.

 

The diagnosis is usually made with a combination of clinical signs and symptoms. An ultrasound can be used to confirm the diagnosis.

Posterior-anterior chest radiographs remain the standard examination in patients with suspected pneumothorax and may be combined with lateral radiographs in difficult cases. The radiographic hallmark is the displacement of the pleural line and the absence of lung markings between the edge of the pleura and chest wall.

Scheme of closed, open and tension pneumothorax

Available at: https://www.vectorstock.com/royalty-free-vector/types-of-pneumothorax-vector-23094759 (Accessed: 13 November 2019).

Ultrasound examination

Ultrasound has a sensitivity of 78%-90% in diagnosing traumatic pneumothorax in comparison to 39%-52% with chest radiographs.

In pneumothorax, there is air in the lungs that will rise to the dependent area of the chest. When the patient is in the supine position, we look for air in the anterior region of the chest in the mid-clavicular line at the second to fourth intercostal space. But in the upright patient (e.g., patients in respiratory distress), air will accumulate in the apicolateral location. The presence of the clavicles makes this area less accessible for imaging, thus increasing the possibility of missing a small pneumothorax.

Based on the above, the patient is scanned in a supine or near-to-supine position to allow the visualization of at least two ribs with the pleural line between them. This minimizes the risk of mistaking the rib border for a non-moving pleural line. The pleural line should be visualized at multiple intercostal spaces (2nd to 4th) and from medial to lateral in the presumed least dependent zone of the thorax. A comparison with findings on the contralateral side may facilitate the interpretation.

Air collection (blue) in the apical region in a sitting and supine position

Available at: https://www.youtube.com/watch?v=WOlz8-km6hE&t=176s (Accessed: 13 November 2019).

Probe position when evaluating pleural sliding PAME Maribor
Probe position when evaluating pleural sliding PAME Maribor
Collection of air between parietal and visceral pleura

Source: Hansel, J., & Privšek, M. (2016). PACE: POCUS Assisted Clinical Examination - A Modular Curriculum for teaching Point-of-Care Ultrasound to Undergraduate Med Students.

The absence of lung sliding

In pneumothorax, there is air between the visceral and parietal pleura, and the visualization of the parietal pleura is not possible. The lung sliding is absent in a situation like this.

  • the visceral and parietal pleurae are split because of the air,
  • lack of lung sliding does not always indicate pneumothorax – the clinical correlation is always required.
Absence of pleural sliding PAME Maribor

Barcode sign and seashore sign

When M mode is applied to the lung exam, the system displays a representation of tissue motion over time. In the case of normal lung sliding, there is a significant scatter resulting from lung sliding. Therefore, the area below the parietal pleura on the M mode takes on a granular or “sandy” appearance while the relatively immobile superficial tissues appear smooth and linear. This is the so-called “seashore sign,” as the superficial tissues resemble waves and the deeper tissues a sandy beach. The normal lung on ultrasound shows lung sliding with granular moving artifacts, which appear as seashores on M mode.

When lung sliding is not present, the superficial and deep tissues both appear smooth and linear, resulting in the classic “barcode sign“. This sing indicates a pneumothorax at the examined intercostal space.

Seashore sign

Stone, M. (2008) 'Ultrasound diagnosis of traumatic pneumothorax', Journal of Emergencies, Trauma and Shock, 1(1), 19. doi:10.4103/0974-2700.41788 Seashore Vectors. Available at: https://www.freepik.com/free-photos-vectors/seashore 1 (Accessed: 13 November 2019)

»Seashore and barcode sign« comparison

Available at: http://www.thepocusatlas.com/ (Accessed: 13 November 2019)

B-lines

For a comprehensive review of B-lines click here.

A-lines

For a comprehensive review of A-lines click here.

Lung point sign

Another sign, called the lung point sign, can be seen on the border of pneumothorax. It can be observed because sliding lungs intermittently come into contact with the chest wall during inspiration. It helps determine the actual size of pneumothorax. The sign has a 100% specificity and 66% sensitivity for pneumothorax. If there is a lack of lung sliding anteriorly on the chest wall, the probe can be moved slowly more lateral and posterior on the chest wall to find the lung point sign.

When a lung point is encountered, a pattern that alternates between “seashore” and “barcode” is seen, as normal lungs intermittently slide into the plane of the M mode tracing.

The more lateral or posterior the lung point is seen, the bigger is the pneumothorax. Therefore, if the point is located at an anterior location, then the pneumothorax is relatively small. In the case of total lung collapse (i.e., large pneumothoraces where there is no lung tissue in contact with the pleura), a lung point sign is not seen.

It is observed at the boundary between the pneumothorax (where there is no apposition of the pleura, so no lung sliding is seen) and the partially deflated lung (where there is still an apposition of the two pleural surfaces, so lung sliding is seen).

It is a junction of slide/no slide – the exact point where the air begins to separate the parietal and visceral pleura.

Lung point PAME Maribor

Lung point PAME Maribor

Pleural effusion

Pleural effusion is an abnormal amount of fluid in pleural cavity (around the lungs in the pleural space). Pleural space plays an important role in respiration and normally there is small amount of fluid (around 0.13 mL/kg of body weight) inside the pleural space, which serves as a lubricant for the pleural surfaces movement. This amount of fluid is maintained through the balance of hydrostatic and oncotic pressure and lymphatic drainage, a disturbance of which may lead to pathology. Pleural effusion is usually a result of excess fluid production or decreased absorption or both.

There are several different conditions that can lead to pleural effusion. It is especially important to determine the cause because solving the cause will also solve the pleural effusion (beside pleural drainage if needed). However, untreated or inappropriately treated parapneumonic effusions may lead to empyema, constrictive fibrosis, and sepsis.

The most common causes for pleural effusion are:

  • congestive heart failiure
  • liver or kidney disease
  • infection (eg. pneumonia, tuberculosis)
  • malignancy (most commonly lung or breast cancer, lymphoma, leukemia)
  • pulmonary embolism
  • autoimmune disorders (eg. lupus erythematosus (LE), rheumatoid arthritis (RA), …)
  • chest trauma
Anatomic scheme of pleural effusion and surrounding anatomical structures

https://upload.wikimedia.org/wikipedia/commons/4/48/Diagram_showing_a_build_up_of_fluid_in_the_lining_of_the_lungs_%28pleural_effusion%29_CRUK_054.svg (Accessed: 13 November 2019).

Based on the mechanism of the fluid formation pleural effusions are usually divided into transudates and exudates.

Transudate pathophysiological mechanism is imbalance in oncotic and hydrostatic pressures (congestive heart failiure, cirrhosis, atelectasis, hypoalbuminemia, nephrotic syndrome, peritoneal dialysis, myxedema, …), whereas exudate results from inflammation of the pleura or decreased lymphatic drainage (pneumonia and parapneumonic causes, malignancy, collagen-vascular conditions (LE, RA), tuberculosis, trauma, postcardiac injury syndrome, pancreatitis, esophageal rupture, …). It is also possible for pleural effusion to result from both mentioned mechanisms.

Symptoms of pleural effusion may contain any of the listed ones but it is also possible for the patient to present asymptomatic:

  • shortness of breath
  • chest pain (it is usually described as pleutiric pain – results from pleural irritation and is usually described as sharp or stabbing and is exacerbated with deep inspiration; NOTE – pain may diminish in intensity as the pleural effusion increases in size and the inflamed pleural surfaces are no longer in contact with each other!)
  • cough (often mild and nonproductive, if productive or severe it can indicate an inflammatory underlying condition, such as pneumonia)
  • other occuring symptoms may indicate the underlying condition

Physical examination:

If the effusion is smaller than 300 mL the patient is usually asymptomatic. When the effusion exceeds 300 mL, the physical examination findings may include:

  • percussion dullness at the point of pleural effusion,
  • decreased tactile fremitus,
  • asymmetrical chest expansion (diminished or delayed expansion on the side of the effusion)
  • mediastinal shift with tracheal displacement to the side opposite of the effusion (when the effusion exceeds 1000 mL)
  • silenced breath sounds
  • pleural rubbing

Other physical examination deviations usually indicate the underlying condition.

Considering differential diagnosis it is important to distinguish between transudate and exudate in order to narrow the possible causes of pleural effusion.
The fluid is defined as exudate if any of the following measurements is found:

  • pleural fluid vs. serum protein ratio greater than 0,5
  • pleural fluid vs. serum LDH ratio greater than 0,6
  • pleural fluid LDH is greater than two thirds of the upper normal serum value limit

If all of the above are absent the fluid is considered a transudate.

However, one must never forget about clinical judgement, especially when the test results are near the cut off points of measurements. When assessing the pleural effusion fluid one must also check LDH, glucose and pH levels, cell count, cultures and cytology. Additional laboratory test are not routinely made but are warranted when we suspect a specific etiology.

Chest X-ray: pleural effusions of more than 175 mL are usually apparent as blunting of the costophrenic angle on upright posteroanterior chest radiographs.

CT scan: should be performed in all patients with an undiagnosed pleural effusion.

Left pleural effusion with positive spine sign and left pleural effusion, PAME Maribor
Pleural effusion with air bronchogram and pleural effusion with positive spine sign, PAME Maribor

Available at: https://radiopaedia.org/cases/pleural-effusion-7 (Accessed; 13 November 2019).

Chest X-ray of pleural effusion (right hemithorax)

Available at: https://radiopaedia.org/cases/pleural-effusion-7 (Accessed; 13 November 2019).

Ultrasound examination

The probe of choice for assessing pleural effusion is curvilinear but one can also use cardiac probe. The patient lies in supine position. Sometimes it is helpful if the patient is sitting – in that case the fluid will collect in the bases of thoracic cavity. We place the probe in the mid axillary line with small corrections anteriorly or posteriorly from patient to patient – we are searching for the lowest part of thoracic cavity. The probe indicator should be pointing cranially. To get rid of the ribs we can rotate the transducer parallel to the ribs into the intercostal space – this is how we get the clearest picture.

Transducer movement and effusion position in seated patient.

Available at: https://litfl.com/lung-ultrasound-pleural-effusion/ (Accessed: 13 November 2019).

Pleural effusion accessibility in different patient positions.

Available at: https://litfl.com/lung-ultrasound-pleural-effusion/ (Accessed: 13 November 2019).

Transducer pathway in different patient positions.

Available at: https://litfl.com/lung-ultrasound-pleural-effusion/ (Accessed; 13 November 2019).

We can assume the presence of pleural effusion by assessing (or checking for) three main ultrasound changes:

  • hypo- or anechoic structure (fluid) in the lung bases
  • negative mirror sign
  • positive spine sign

Transudate should give the appearance of normal (anechoic) pleural fluid. Exudate on the other hand can in some cases have similar echo texture as the liver or the spleen. In this case the mirror sign would not be present but one can see positive spine sign – those two phenomenas help us to distinguish between exudate and healthy lung tissue in the lung recesses. Although all the differences between transudate and exudate it is hard to distinguish them with ultrasound as they can both have an anechoic appearance.

Pleural effusion and surrounding anatomical structures.

Killu K, Dulchavsky S, Coba V. (2010) 'The ICU Ultrasound Pocket Book', 1st Edition.

Anechoic pleural effusion.

Killu K, Dulchavsky S, Coba V. (2010) 'The ICU Ultrasound Pocket Book', 1st Edition.

Echoic pleural effusion with septations (characteristic for exudate).

Killu K, Dulchavsky S, Coba V. (2010) 'The ICU Ultrasound Pocket Book', 1st Edition.

Hemothorax

Hemothorax is a collection of blood in the space between the chest wall and the lung (the pleural cavity). Massive hemothorax is defined as an initial blood loss of more than 1.5 liters of blood or as continuing blood loss of more than 200 ml/h in 2-4 hours.

Possible causes may include chest trauma, lung or pleural cancer, defect of the blood clotting mechanism, thoracic or heart surgery, or pulmonary infarction (death of lung tissue).

Depending on the amount of blood or air in the pleural cavity, a collapsed lung can lead to respiratory and hemodynamic failure (tension pneumothorax).

Symptoms of hemothorax

  • breathlessness, chest pain, and occasionally lightheadedness;
  • reduced or absent breath sounds and reduced movement of the chest wall on the affected side;
  • percussion: a dull sound;
  • tachycardia,  pale, cool, clammy skin, and cyanosis.

Ultrasound appearance of hemothorax:

Ultrasound is more sensitive than x-ray as it can detect as little as 20 ml of fluid compared with 50–100 ml and 175 ml for upright and supine chest radiographs.

A sensitivity for ultrasonography in the diagnosis of hemothorax is 82.97%, with a specificity of 98.05%, a positive predictive value of 90%, and a negative predictive value of 92.66%.

Blood appears anechoic (black) when the hemothorax is acute and free-flowing, but hypoechoic (gray) when subacute or clotted.

Hemothorax

Available at: https://www.rcemlearning.co.uk/reference/thoracic-trauma/ (Accessed: 19 November 2019).

Fibrothorax

Fibrothorax is a condition characterized by the accumulation of fibrous tissue in the pleural cavity in reaction to undrained pleural fluid, where a thick “peel” can form on either pleural surface, eventually preventing the complete expansion of lungs. The main insult is the presence of an undrained pleural effusion that may result from any of these conditions: empyema, hemothorax, undrained pleural effusion, recurrent effusions after open-heart surgery, chronic pneumothorax, tuberculosis or asbestos exposure. An inflammatory response in the pleural space causes fibrin deposition and formation of a collagen-rich “peel”, covering both the parietal and visceral pleurae.

Undrained pleural effusion already has a space-occupying effect compressing the lung parenchyma. If the organization of the fibrotic peel continues, this results in the restrictive pathophysiologic pattern of lung disease. Consequently, hypoxic pulmonary vasoconstriction limits blood flow and results in ventilation/perfusion mismatches leading to pulmonary hypertension.

Depending on the degree of parenchymal involvement, symptoms may vary. Hypoxia may be absent at rest; however, desaturation can be seen with exercise. Patients with fibrothorax may be asymptomatic or complain of dyspnea. The dyspnea is the most common symptom followed by chest discomfort and nonproductive cough. Patients usually present with a recurrent or persistent pleural effusion that can be easily correlated with a traumatic event and/or injury.

Clinicians may detect signs such as decreased chest wall movement, decreased breath sounds, and dullness to percussion.

The most effective treatment of fibrothorax is prevention. Early treatment of hemothorax and recurrent pleural effusions with chest tube drainage or thoracoscopy within the first few weeks of injury may avoid the formation of the thick fibrous peel. If the thoracoscopy is not performed, the surgery is needed to remove the fibrous peel – this is called decortication.

Ultrasound appearance:

The ultrasound finding associated with fibrothorax is thickened, echogenic rind of pleural plaque that parallels the ribs.

Fibrosis has different echogenicities. Newly developed fibrosis may be very hypoechogenic. Thus it is sometimes misinterpreted as effusion, usually hypoechoic. The older fibrosis tends to be more echogenic. Calcifications are present sometimes in the thickened pleura, more often in tuberculosis or empyema.

Pleural drainage

Pleural drainage is a procedure by which fluid or air is removed from the pleural space – the space between the visceral and parietal pleura. The drainage system consists of a tube inserted into the pleural space. The other end of the drainage tube is connected to the negative pressure sucking machine, which sucks the fluid or air out of the body.

Using ultrasound to image the thoracic cavity, we can find excessive fluid called fluidothorax or excessive air called pneumothorax. For drainage, we typically insert the tube in the 4th or 5th intercostal space in the anterior or mid-axillary line. We can find the intercostal vein, artery, and nerve in the upper part of each intercostal space with ultrasound. If tension pneumothorax is suspected, the needle decompression is usually performed. The procedure includes placing a needle through the second intercostal space in the midclavicular line.

Location of pleural drainage.

Vetrugno, L. et al. (2018) ‘An easier and safe affair, pleural drainage with ultrasound in critical patient: a technical note’, Critical Ultrasound Journal. Springer-Verlag Italia s.r.l., 10(1), p. 18. doi: 10.1186/s13089-018-0098-z.

US guided pleural drainage

Vetrugno, L. et al. (2018) ‘An easier and safe affair, pleural drainage with ultrasound in critical patient: a technical note’, Critical Ultrasound Journal. Springer-Verlag Italia s.r.l., 10(1), p. 18. doi: 10.1186/s13089-018-0098-z.

Resources

Basics of Lung Ultrasound for the Nephrologist: What are A-lines and B-lines? - Renal Fellow Network. Urology of Virginia. Available at: https://www.urologyofva.net/articles/category/nephrology/3049084/basics-of-lung- ultrasound-for-the-nephrologist-what-are-a-lines-and-b-lines-renal-fellow-network (accessed October 30, 2019).

Gargani, L. and Volpicelli, G. (2014) ‘How i do it: Lung ultrasound’, Cardiovascular Ultrasound. BioMed Central Ltd., 12(1), p. 25. doi: 10.1186/1476-7120-12-25.

Lichtenstein D. (2005) ‘General ultrasound in critically ill’, Berlin, Heidelberg, New York: Springer.

Lichtenstein D. (2005) ‘General ultrasound in critically ill’, Berlin, Heidelberg, New York: Springer.

Boron WF, Boulpaep EL. (2017) Medical Physiology. Phiadelphia: Elsevier.

Charalampidis C, Youroukou A, Lazaridis G, et al. (2015) Pleura space anatomy. J Thorac Dis.;7(Suppl 1):S27-32.

Husain, L. et al. (2012) ‘Sonographic diagnosis of pneumothorax’, Journal of Emergencies, Trauma, and Shock. Medknow Publications and Media Pvt. Ltd., 5(1), p. 76. doi: 10.4103/0974-2700.93116.

Bedside Ultrasound for Pneumothorax The Sliding Lung Technique. Available at: https://www.teleflex.com/anz/en/australia-education/clinical-resources/Sliding-Lung-Technique-102016.pdf (Accessed: 13 november 2019)

Complete Learning Platform for Medical Students. Available at: https://www.amboss.com/us/knowledge/Pneumothorax (Accessed: 13 November 2019)

Goffi, A., Kruisselbrink, R. and Volpicelli, G. (2018) ‘The sound of air: point-of-care lung ultrasound in perioperative medicine’, Canadian Journal of Anesthesia. Springer New York LLC, pp. 399–416. doi: 10.1007/s12630-018-1062-x.

Source: Hansel, J., & Privšek, M. (2016). PACE: POCUS Assisted Clinical Examination - A Modular Curriculum for teaching Point-of-Care Ultrasound to Undergraduate Med Students.

Husain, L. et al. (2012) ‘Sonographic diagnosis of pneumothorax’, Journal of Emergencies, Trauma, and Shock. Medknow Publications and Media Pvt. Ltd., 5(1), p. 76. doi: 10.4103/0974-2700.93116.

Khaladkar, S. M. et al.‘Diagnosis and signs of pneumothorax on ultrasound with radiological review’. Available at: www.ijhbr.com (Accessed: 13 November 2019)

Mayo, P. (2018). Bedside pleural ultrasonography: Equipment, technique, and the identification of pleural effusion and pneumothorax. Available at: https://www.uptodate.com/contents/bedside-pleural-ultrasonography-equipment-technique-and-the-identification-of-pleural-effusion-and-pneumothorax (Accessed: 13 November 2019)

Papagiannis, A. et al. (2015) ‘Pneumothorax: An up to date “introduction”’, Annals of Translational Medicine. AME Publishing Company, 3(4). doi: 10.3978/j.issn.2305-5839.2015.03.23.

Raheja, R. et al. (2019) ‘Application of Lung Ultrasound in Critical Care Setting: A Review’, Cureus. Cureus, Inc., 11(7). doi: 10.7759/cureus.5233.

Retief, J. and Chopra, M. (2017) ‘Pitfalls in the ultrasonographic diagnosis of pneumothorax’, Journal of the Intensive Care Society. SAGE Publications Inc., 18(2), pp. 143–145. doi: 10.1177/1751143716681034.

Roberts, D. J. et al. (2014) ‘Clinical manifestations of tension pneumothorax: Protocol for a systematic review and meta-analysis’, Systematic Reviews. BioMed Central Ltd., 3(1). doi: 10.1186/2046-4053-3-3.

TPA. Available at: http://www.thepocusatlas.com/ (Accessed: 13 November 2019) Tschopp, J. M. et al. (2015) ‘ERS task force statement: Diagnosis and treatment of primary spontaneous pneumothorax’, European Respiratory Journal. European Respiratory Society, 46(2), pp. 321–335. doi: 10.1183/09031936.00219214.

WebMD. Available at: https://www.webmd.com/lung/pleural-effusion-symptoms-causes-treatments (Accessed: 19 Novemer 2019).

Medscape. Available at: https://emedicine.medscape.com/article/299959-overview#a6 (Accessed: 19 November 2019).

CORE ULTRASOUND. Available at: https://www.coreultrasound.com/pleural-effusions-part-1/ (Accessed: 19 November 2019).

Lung Ultrasound: Pneumonia • LITFL • Ultrasound library. Available at: https://litfl.com/lung-ultrasound-pleural-effusion/ (Accessed: 19 November 2019).

MedicalNewsToday. Available at: https://www.medicalnewstoday.com/articles/318021#causes (Accessed: 19 November 2019). Killu K, Dulchavsky S, Coba V. (2010) 'The ICU Ultrasound Pocket Book', 1st Edition.

Brooks, A. et al. (2004) ‘Emergency ultrasound in the acute assessment of haemothorax’, Emergency Medicine Journal. Emerg Med J, 21(1), pp. 44–46. doi: 10.1136/emj.2003.005438. Plankton sign (ultrasound): Radiology Reference Article. Available at: https://radiopaedia.org/articles/plankton-sign-ultrasound (Accessed: 14 November 2019).

Ojaghi Haghighi, S. H. et al. (2014) ‘Ultrasonographic diagnosis of suspected hemopneumothorax in trauma patients’, Trauma Monthly. Kowsar Medical Publishing Company, 19(4), pp. 5–8. doi: 10.5812/traumamon.17498.

Hemothorax following chest trauma. Available at: https://sonoworld.com/CaseDetails/Hemothorax_following_chest_trauma.aspx?ModuleCategoryId=568 (Accessed: 14 November 2019).

Hemothorax. Available at: https://www.wikiwand.com/en/Hemothorax (Accessed: 14 November 2019)

Hilendarov, A., Velkova, K., Georgiev, A., Siracov, N., & Tchervenkov, L. (2018) ‘Ultrasound diagnosis of traumatic hemothorax’, International Journal of Radiology & Radiation Therapy, 5(4). doi:10.15406/ijrrt.2018.05.00177.

Lichtenstein, D. A. (2007). General ultrasound in the critically ill. Berlin: Springer. TRAUMA/HEMORRHAGE. Available at: http://www.erpocketbooks.com/er-ultrasounds/trauma-ultrasounds-from-the-ed/ (Accessed: 14 November 2019)

Alhassan, S., Fasanya, A., & Thirumala, R. (2017) ‘Extensive Calcified Fibrothorax’, American Journal of Respiratory and Critical Care Medicine, 195(4). Doi: 10.1164/rccm.201606-1265im. Chira, R., Chira, A. & Mircea, PA. (2011) 'Thoracic wall ultrasonography-normal and pathological findings. Pictorial essay', Medical Ultrasonography, 13(3):228-233.

Dietrich, C. F. (2012). EFSUMB course book on ultrasound. London: EFSUMB. Papadakos, P. J., & Gestring, M. L. (2015). Encyclopedia of trauma care. Berlin: Springer Reference.

Sperandeo, M. et al. (2008) ‘Role of thoracic ultrasound in the assessment of pleural and pulmonary diseases’, Journal of Ultrasound. J Ultrasound, 11(2), pp. 39–46. doi: 10.1016/j.jus.2008.02.001.

Strzalka, CT., & Yost, MF. (2002) 'Treatment of fibrothorax using intrapleural tissue plasminogen activator', Hospital Physician, 65–67.

Sugarbaker, D. J. (2015). Adult chest surgery. New York: McGraw-Hill Education.

Porcel, J. M. (2018) ‘Chest Tube Drainage of the Pleural Space: A Concise Review for Pulmonologists’, Tuberculosis and Respiratory Diseases. Korean National Tuberculosis Association, pp. 106–115. doi: 10.4046/trd.2017.0107.

Prosen G et al. (2014). Šola urgence- zbornik predavanj. Available at: http://www.szum.si/media/uploads/files/Zbornik%20Sola%20urgence%201_%20letnik%20FINAL%20VERZIJA%201_1.pdf (Accessed: 29 October 2019)