PART ONE

Dr WALIF CHBEIR

Edited March02,2016

* We searched Medline and google for articles relating to Pneumothorax with focus

on imaging appearances and diagnostic approach. We also consult a book.

* No financial relationships with commercial entities to disclose.

I- Definition

PNO is air in the pleural space causing partial or complete lung collapse.

II-Etiology

* Primary spontaneous pneumothorax (PSP) occurs in patients without

underlying pulmonary disease. It is thought to be due to spontaneous rupture of

subpleural apical blebs or bullae that result from smoking or that are inherited.

* Secondary spontaneous pneumothorax (SSP) It most often results from rupture

of a bleb or bulla in patients with underlying pulmonary disease. SSP is more serious

than PSP because it occurs in patients whose underlying lung disease decreases

their pulmonary reserve.

–Most common:

– Chronic obstructive pulmonary disease

– Asthma

– Cystic fibrosis

– Pneumonia: Pneumocystis jirovecii infection / Tuberculosis /

Bacterial pneumonia.( Cavitary or Necrotizing) .

– ARDS

— Less common: – About 0.5% of pneumothoraces are associated with lung metastases, of

which 89% are caused by sarcomas, with osteogenic sarcoma being the most common

– Langerhans cell histiocytosis

– Lymphangioleiomyomatosis/tuberous sclerosis .

– Sarcoidosis.

– Connective tissue disorders: Ankylosing spondylitis , Ehlers-

Danlos syndrome, Marfan syndrome, Polymyositis and dermatomyositis, RA,

Systemic sclerosis.

– Catamenial pneumothorax: is a rare form of SSP that occurs

within 48 h of the onset of menstruation in premenopausal women and sometimes in

postmenopausal women taking estrogen . The cause is intrathoracic endometriosis,

possibly due to migration of peritoneal endometrial tissue through diaphragmatic

defects or embolization through pelvic veins.

* Traumatic pneumothorax is a common complication of penetrating or blunt chest

injuries.

– In patients with penetrating wounds that traverse the mediastinum,or with severe

blunt

trauma, pneumothorax may be caused by disruption of the tracheobronchial tree. Air

from

the pneumothorax may enter the soft tissues of the chest and/or neck (subcutaneous

emphysema), or mediastinum (pneumomediastinum).

– Iatrogenic pneumothorax is caused by medical interventions, including

transthoracic needle aspiration and Biopsy, thoracentesis, Thoracotomy, central

venous catheter placement, mechanical ventilation and barotrauma, and

cardiopulmonary resuscitation. Also: Surgical procedures in the thorax, head, or neck.

and Abdominal procedures using bowel or peritoneal distension.

III- Symptoms and Signs ( + PhysioPatho)

* Small pneumothoraces are occasionally asymptomatic.

* Symptoms of pneumothorax typically include pleuritic chest pain and shortness of

breath.

– Dyspnea may be sudden or gradual in onset depending on the rate of development

and size of the pneumothorax.

– Pain can simulate pericarditis, pneumonia, pleuritis, pulmonary embolism,

musculoskeletal injury (when referred to the shoulder), or an intra-abdominal process

(when referred to the abdomen). Pain can also simulate cardiac ischemia, although

typically the pain of cardiac ischemia is not pleuritic.

– Physical findings classically consist of absent tactile fremitus, hyperresonance to

percussion, and decreased breath sounds on the affected side. If the pneumothorax

is large, the affected side may be enlarged with the trachea visibly shifted to the

opposite side. With tension pneumothorax, hypotension can occur.

. Importantly, the volume of the pneumothorax can show limited correlation with the

intensity of the symptoms experienced by the victim, and physical signs may not be

apparent if the pneumothorax is relatively small.

* Primary Spontaneous Pneumothorax (PSP) :

– Classically in tall, thin, asthenic men. Most patients are between 20 and 40 years of

age, and the male-to-female ratio is approximately 5 to 1. It is thought to be due to

spontaneous rupture of subpleural apical blebs or bullae that result from smoking or

that are inherited. It generally occurs at rest, although some cases occur during

activities involving reaching or stretching. PSP also occurs during diving and highaltitude

flying .

– It usually causes limited symptoms. Chest pain and sometimes mild breathlessness are the

usual predominant presenting features. People who are affected by PSPs are often unaware of

potential danger and may wait several days before seeking medical attention. PSPs more

commonly occur during changes in atmospheric pressure, explaining to some extent why

episodes of pneumothorax may happen in clusters. It is rare for PSPs to cause tension

pneumothoraces.

* Secondary Spontaneous Pneumothorax: Symptoms in SSPs tend to be more severe than

in PSPs, as the unaffected lungs are generally unable to replace the loss of function in the

affected lungs. Hypoxemia is usually present and may be observed as cyanosis. Hypercapnia

is sometimes encountered; this may cause confusion and if very severe may result in comas.

The sudden onset of breathlessness in someone with COP), cystic fibrosis, or other serious lung

diseases should therefore prompt investigations to identify the possibility of a pneumothorax.

* Traumatic pneumothorax (TP) Traumatic pneumothoraces have been found to occur in up

to half of all cases of chest trauma, with only rib fractures being more common in this group.

The pneumothorax can be occult (not readily apparent) in half of these cases, but may enlarge

particularly if mechanical ventilation is required. They are also encountered in patients already

receiving mechanical ventilation for some other reason.

– Many patients also have a hemothorax (hemopneumothorax).

– In patients with penetrating wounds that traverse the mediastinum or with severe

blunt trauma, pneumothorax may be caused by disruption of the tracheobronchial

tree.

– Air from the pneumothorax may enter the soft tissues of the chest and/or neck

(subcutaneous

emphysema), or mediastinum (pneumomediastinum).

– Patients commonly have pleuritic chest pain, dyspnea, tachypnea, and

tachycardia.

– Breath sounds may be diminished and the affected hemithorax hyperresonant to

percussion—mainly with larger pneumothoraces. However, these findings are not

always

present and may be hard to detect in a noisy resuscitation setting.

– Subcutaneous emphysema causes a crackle or crunch when palpated; findings

may be localized to a small area or involve a large portion of the chest wall and/or

extend to the neck; extensive involvement suggests disruption of the

tracheobronchial tree.

– Air in the mediastinum may produce a characteristic crunching sound

synchronous with the heartbeat (Hamman sign or Hamman crunch), but this finding is

not always present and also is occasionally caused by injury to the esophagus.

* Open pneumothorax

– Some patients with traumatic pneumothorax have an unsealed opening in the

chest wall. when the opening is sufficiently large, the ventillation on the affected side

is eliminated respiratory mechanics are impaired and the inability to ventilate the

lungs causes respiratory distress and respiratory failure.

* Tension pneumothorax ( TP) is accumulation of air in the pleural space under

pressure,

compressing the lungs and decreasing venous return to the heart. Although multiple

definitions exist, a tension pneumothorax is generally considered to be present when a

pneumothorax leads to significant impairment of respiration and/or blood circulation.

– Tension pneumothorax develops when a lung or chest wall injury is such that it

allows air

into the pleural space but not out of it (a one-way valve). As a result, air accumulates

and

compresses the lung, eventually shifting the mediastinum, compressing the

contralateral

lung, and increasing intrathoracic pressure enough to decrease venous return to the

heart,

causing shock. These effects can develop rapidly, particularly in patients undergoing

positive pressure ventilation.

– Causes include patients receiving positive-pressure ventilation (most commonly) with

mechanical ventilation or particularly during resuscitation, failed central venous

cannulation, simple (uncomplicated) pneumothorax with lung injury that fails to seal

following penetrating or blunt chest trauma and in patients with lung disease.

– Symptoms and signs initially are those of simple pneumothorax, tachypnea and

increased heart rate . As intrathoracic pressure increases, patients develop

hypotension, tracheal deviation, neck vein distention and respiratory distress.

The affected hemithorax is hyperresonant to percussion with reduced expansion and

often feels somewhat distended, tense, and poorly compressible to palpation. Rarely,

there may be cyanosis, altered level of consciousness.

– Recent studies have shown that the development of tension features may not always be as

rapid as previously thought. Deviation of the trachea to one side and the presence of raised

jugular venous pressure (distended neck veins) are not reliable as clinical signs.

– In case of Tension pneumothorax occuring in someone who is receiving mechanical

ventilation, it may be difficult to spot as the person is typically receiving sedation; it is often

noted because of a sudden deterioration in condition.

– This is a medical emergency and may require immediate treatment without further

investigations. Without appropriate treatment, the impaired venous return can cause

systemic hypotension and respiratory and cardiac arrest (pulseless electrical

activity) within minutes.

* Acute respiratory distress syndrome, critically ill adults and pneumothorax:

– pneumothorax is common in ventilated critically ill patients . Approximately 50% of

patients with ARDS who require mechanical ventilation will develop a pneumothorax

during their treatment. The ARDS damages the lung parenchyma, and the high

intrathoracic pressures resulting from mechanical ventilation of stiff lungs contributes

to rupture of the diseased lung tissue.

– In patients with minimal pulmonary reserve, even a small pneumothorax can have

adverse hemodynamic effects or cause tension that rapidly induces cardiovascular

collapse and death.

– Many factors may precipitate the occurrence of pneumothorax in ARDS, such as the

mechanical ventilation settings, the clinical severity of ARDS and the underlying

pulmonary pathology (like preexisting emphysema).

– Up to 96% of patients who develop pneumothorax while receiving ventilation will

progress to tension pneumothorax because the machine blows air out of the hole in

the lung into the pleural space with positive pressure.

– Tension pneumothorax occurs when intrapleural pressure exceeds atmospheric

pressure. Tension pneumothorax is a clinical diagnosis, not a radiographic diagnosis,

because the respiratory and hemodynamic consequences of tension pneumothorax

do not have radiographic equivalents in many circumstances.

. Radiographic signs of tension (mediastinal shift, inversion of diaphragm,

enlargement of affected hemithorax) can occur in the absence of adverse physiologic

effects, and the physiologic effects of pleural tension may be present without

radiographic signs of tension. In ARDS, the diseased noncompliant lung may not

collapse in the presence of a pneumothorax, and the controralateral lung may be too

stiff to allow mediastinal shift. Thus, tension pneumothorax in ARDS can present as a

loculated paracardiac or subpulmonic air collection with little or no mediastinal shift

and only slight changes of the cardiac contour. ++++

. Also, In patients with severe ARDS and pleural adhesions, most if not all of

cardinal clinical signs of Tension PNO (sudden increase in ventilation pressures,

severely reduced breath sounds on the affected side, jugular venous distention, and

the dreaded mediastinal shift) that results in cardiovascular collapse will be absent.

The lung may be so diseased, stiff and noncompliant that it does not fully collapse

when air trapped in the pleural space presses on it. If only a small portion of the lung

is externally compressed, the mediastinum will not be affected Therefore,

radiographic evidence of extrapulmonary air collections becomes even more

important in this group of critically ill patients.

. Adherence of inflamed pleura to the chest wall ( parietal pl) may confine a

pneumothorax to a loculated portion of the pleural space around the site of the air

leak. Even daily chest radiographs can miss small loculated pneumothoraces. Two

studies reported by Chon and colleagues (cf num ref) reported that in critically ill,

mechanically ventilated adults, 33% to 50% of “missed” pneumothoraces (that is,

pneumothoraces too small or subtle to be seen on the radiograph until retrospective

review) progressed to tension. Even small areas of compression on the lung can have

a significant impact on pulmonary function when the lungs are so dysfunctional to

begin with.

– The most repeatable finding of PNO in patients with severe ARDS was a subtle

drop in oxygenation measurements. Patients showed an improvement in PaO2

within 24 hours of chest tube insertion and pneumothorax resolution.

. Loculated pneumothorax provides only subtle clinical clues. The only clinical

evidence may be deteriorating oxygenation without another obvious cause.

. The early and accurate diagnosis of pneumothorax in ARDS patients is

mandatory since this complication carries an increased mortality. Furthermore, small

pneumothoraces in these patients can cause severe hemodynamic or pulmonary

compromise. This is the reason why pneumothorax must always be suspected in any

patient with ARDS who experiences an acute worsening in respiratory function,

accompanied with dyspnea and hypoxemia, which is usually unresponded to oxygen

therapy.

. Although non-specific, the association of respiratory and haemodynamic

signs found with a tension pneumothorax are a medical emergency. Severe

haemodynamic compromise will require urgent needle decompression of the

pneumothorax before its diagnosis being confirmed radiologically. Fortunately this

situation is uncommon and there is frequently time for radiological investigations to

help establish the diagnosis of a simple pneumothorax.

* Complications of PNO

– In most reported series, the rate of recurrence of spontaneous pneumothorax on

the same side is as much as 30%.

– On the contralateral side, the rate of recurrence is approximately 10%.

– Other complications include the following: Reexpansion pulmonary edema .

Bronchopleural fistula Occurs in 35% of patients, Pneumomediastinum and

pneumopericardium and Tension pneumothorax. Tension PNO may occur after

spontaneous pneumothorax, although it is more common after traumatic

pneumothorax or with mechanical ventilation.

* In summary: A simple unilateral pneumothorax, even when large, is well tolerated

by most patients unless they have significant underlying pulmonary disease. However,

tension

pneumothorax can cause severe hypotension, and open pneumothorax can

compromise ventilation.

Part Two

IV- Imaging

A- Chest radiography

* Chest radiography is the first investigation performed to assess pneumothorax, because it is simple, inexpensive, rapid, and noninvasive. Traditionally a plain radiograph of the chest, ideally with the Xray beams being projected from the back (posteroanterior, or “PA”), has been the most appropriate first investigation. These are usually performed during maximal inspiration (holding one’s breath). As little as 50 mL of pleural gas may be visible on a chest radiograph, however, it is much less sensitive than chest computed tomography (CT) scanning in detecting blebs or bullae or a small pneumothorax.

* As with pleural effusion, the radiographic appearance of pneumothorax depends on the radiographic projection, the patient’s position, and the presence or absence of pleural adhesion and subsequent loculation.

* The radiographic diagnosis of pneumothorax is usually straightforward the outer margin of the visceral pleura ( and lung), known as the pleural line, is separated from the parietal pleura (and chest wall) by a lucent gas space devoid of pulmonary vessels.

— The pleural line may be difficult to detect with a small pneumothorax unless high quality

posteroanterior and lateral chest films are obtained and viewed under a bright light or under windowing and magnification on workstation

— In the upright patient, air rises in the pleural space, mostly in an apicolateral location and separates the lung from the chest wall, allowing the visceral pleural line to become visible as a

thin curvilinear opacity between vessel-containing lung and the avascular pneumothorax space. The (visceral) pleural line appears either straight or convex towards the chest wall and remains fairly parallel to the chest wall.

– May be laterally located with apical pleural adhesions

— Supine position ( Critically ill patient, in ICU, polytraumatism). Supine radiographs are the least sensitive in detecting pneumothorax, requiring 500 mL of pleural gas—10 times more than necessary to detect air in the apicolateral pleural space on an upright chest radiograph.

– If the pneumothorax is small or moderate in size ( in the setting of bronchopulmonary placement of a feeding tube on an abdominal radiograph, p.e.), the lung is not separated from the chest wall laterally or at the apex and therefore the pneumothorax may not be appreciated.

– The juxtacardiac area (or anteromedial pleural recess) , cardiophrenic recess, the lateral chest wall, the subpulmonic space, the posteromedial pleural recess and the costophrenic pleural recesses are the best areas to search for evidence of pneumothorax. +++ . Actually, the highest part of the chest cavity lies anteriorly or anteromedially at the base near the diaphragm, and free pleural air rises to this region

– The anteromedial pleural recess is the least dependent space in the thoracic cavity in a supine patient. A pneumothorax in this location results in a paramediastinal radiolucent band parallel to the cardiac outline, with sharp definition of the cardiac outline, known as the crisp (net) cardiac silhouette sign. An anteromedial pneumothorax may also displace the anterior junction line laterally. This can be differentiated from pneumomediastinum by determining the extent of the air collection. In pneumomediastinum, air spreads bilaterally, outlining the mediastinal structures.

– Subpulmonic pneumothorax results in hyperlucency of the upper abdominal quadrant, a deep lateral costophrenic sulcus (the well-known deep sulcus sign), visualization of the anterior costophrenic sulcus, and sharp delineation of the diaphragm in the presence of an opacified lung. However, hyperlucency of an upper abdominal quadrant may also be seen in the setting of pneumoperitoneum or subphrenic abscess.

– In summary, the signs of pneumothorax in a supine patient (27- Tocino IM, Miller MH, Fairfax WR. Distribution of pneumothorax in the supine and semirecumbent critically ill adult. AJR Am J Roentgenol. 1985;144:901 à 905.)

1- Relative increased lucency of the involved hemithorax 2- Increased sharpness of the adjacent mediastinal margin and diaphragm 3- Deep sulcus sign (Subpulmonic PNO): Deep, sometimes tongue-like, costophrenic sulcus; may be the only sign of PNO. 4-Visualization of the anterior costophrenic sulcus

5- Increased sharpness of the cardiac borders 6- Visualization of the inferior edge of the collapsed lung above the diaphragm 7- Depression of the ipsilateral hemidiaphragm.

* for equivocal cases:

— Lateral or decubitus views are recommended

– On standard lateral views a visceral pleural line may be seen in the retrosternal position or overlying the vertebrae, parallel to the chest wall.

– Shoot-through lateral or decubitus views may be used in ventilated patients or neonates.

— Although the value of expiratory views is controversial and seem to not increase sensitivity for PNO detection, many clinicians still find them useful in the detection of small pneumothoraxes when clinical suspicion is high and an inspiratory radiograph appears normal.

— Decubitus radiography can be helpful in differentiating PNO from apical bullous disease

* Accentuation of the PNO may be obtained with lateral decubitus studies of the appropriate side (for a possible left pneumothorax, a right lateral decubitus film of the chest should be obtained, with the beam centered over the left lung).

* MIMICS +++

1- Differentiating the pleural line of a pneumothorax from that of a skin fold, clothing, vascular lines, tubing, bedding, hair, the walls of bullae and cavities or chest wall artifact is important. Artifactual densities usually do not parallel the course of the chest wall over their entire length.

– Skin folds are straight or only minimally curved, and do not run parallel to the chest wall as with a true visceral pleural line. Careful inspection of the film may reveal that the artifact extends beyond the thorax or that lung markings are visible beyond the apparent pleural line ( or the artefact). In the absence of underlying lung disease, the pleural line of a pneumothorax usually parallels the shape of the chest wall.

– Clothing or bed sheets may produce a similar artefact. Skin folds also form a dense line—sharp on one side and blurred on the other—in contrast to the less dense visceral pleural line.

The latter distinction can, however, be rather subjective. Occasionally, doubt persists. In this situation, repeat radiography after removal of clothing and repositioning of the arm will be conclusive.

– Radio-opaque lines are often seen accompanying the inferior margins of ribs, which may

simulate a visceral pleural line. These are often called subcostal groove. This normal variant is characterised by its faithful relation to the inferior margin of the accompanying rib, whereas visceral pleural lines diverge from the rib to parallel the chest wall. Although usually close to the adjacent rib, companion shadows may sometimes protrude inferiorly for a variable distance, giving a confusing appearance.

2- Avascular bullae or thinwalled cysts or cavities may be mistaken for a loculated pneumothorax (pneumothorax with a pleural adhesion). .

A chest drain inserted into a bullous in the mistaken belief that it is a pneumothorax is not uncommon. This is not surprising as emphysema is a known predisposing factor for a pneumothorax and patients with an exacerbation of their emphysema can present with a fairly sudden worsening of their breathlessness.

The pleural line caused by a pneumothorax usually is bowed at the center toward the lateral chest wall. Unlike pneumothorax, the inner margins of bullae or cysts usually are concave to the chest wall rather than convex and do not conform exactly to the contours of the costophrenic sulcus. Presence of multiple bullae elsewhere in the lung is also cue clue to the diagnosis.

Decubitus radiography can be helpful in differentiating PNO from apical bullous disease. If in doubt about the diagnosis of a pneumothorax treat the patient and not the radiograph, and do not act on the appearances of a radiograph if it does not fit the clinical picture.

3- The medial border of the scapula can imitate a lung edge but once considered can be traced in continuity with the rest of the bone, revealing its true nature.

4- After pleurectomy for recurrent pneumothorax a radioopaque line may be visible at the operative site due to suture material or staples ( Radiological Review of PNO fig 8). This may be misinterpreted as a new air leak, especially if compared with preoperative radiographs or in ignorance of the history of previous surgery.

This patient underwent pleurectomy for recurrent pneumothorax. Suture material at right apex (arrow) is thicker than visceral pleural line and should not be confused with recurrent air leak. Compare with adjacent apical pneumothorax (arrowhead).

5- After removal of chest drain, a straight radio-opaque line is occasionally seen here along the line of the removed tube, known as a “drain track”. This may be misinterpreted as a recurrent

air leak, but its straight course and precise relation to the drain position on the radiograph before removal are usually conclusive. Presumably this finding is due to indentation of the pleura by the drain.

* The British Thoracic Society guidelines divide pneumothoraxes into small and large based on the distance from visceral pleural surface (lung edge) to chest wall, with less than 2 cm being small and more than 2 cm large (means that the pneumothorax occupies about 50% of the hemithorax ) +++. These guidelines have traditionally stated that the measurement should be performed at the level of the hilum with 2 cm as the cutoff, while American guidelines state that the measurement should be done at the apex of the lung with 3 cm differentiating between a “small” and a “large” pneumothorax. The latter method may overestimate the size of a pneumothorax if it is located mainly at the apex, which is a common occurrence.

– A large pneumothorax is an objective indication for drainage.+++

– Clinical Calculator: Pneumothorax Degree of Collapse

PercentPneumo = 100 * (1 – (LungDiameter3 / HemithoraxDiameter3))

The size of a pneumothorax can be defined as the percentage of the hemithorax that is vacant. This percentage is estimated by taking 1 minus the ratio of the cubes of the width of the lung and hemithorax. For example, if the width of the hemithorax is 10 cm and the width of the lung is 5 cm, the ratio is 5 3 /10 3= 0.125. Thus, the size of the pneumothorax is about 1 minus 0.125, or 87.5%. If adhesions are present between the lung and the chest wall, the lung does not collapse symmetrically, the pneumothorax may appear atypical or loculated, and the calculation is not accurate.

http://www.merckmanuals.com/professional/pulmonary-disorders/mediastinal-and-pleural-disorders/pneumothorax

* A large tension pneumothorax can be a life-threatening situation requiring rapid decompression. It can result from penetrating injuries or can arise spontaneously. They are serious because air exchange is compromised in both the lung with the pneumothorax and the opposite lung which is being compressed.

– Radiologic signs of tension pneumothorax include controlateral displacement of Heart and mediastinal structures, inferior displacement or depression of the diaphragm, hyperlucent hemithorax, rib cage expansion and ipsilateral collapse of the lung.

– Any significant degree of displacement of the mediastinum from the midline position on maximum inspiration, as well as any depression of the diaphragm, should be taken as evidence of tension , although a definite diagnosis of tension pneumothorax is difficult to make on the basis of radiographic findings.

. It is not unusual for the mediastinum to be shifted away from the affected lung due to the pressure differences. This is not equivalent to a tension pneumothorax, which is determined mainly by the constellation of symptoms, hypoxia, and shock.

– The degree of lung collapse is an unreliable sign of tension, since underlying lung disease may prevent collapse even in the presence of tension.

* Pleural effusions occur coincident with pneumothorax in 15–25% of patients, but they usually are quite small.

* Hemopneumothorax occurs in 2–3% of patients with spontaneous pneumothorax. Bleeding is believed to represent rupture or tearing of vascular adhesions between the visceral and parietal pleura as the lung collapses.

* The chest radiograph should also be carefully examined for evidence of underlying parenchymal lung disease . The most common of these predisposing to pneumothorax are emphysema, pulmonary fibrosis of any cause, cystic fibrosis, aggressive or cavitating pneumonia, and cystic interstitial lung diseases such as Langerhans’ cell histiocytosis and lymphangiomyomatosis.

— Detection of an underlying condition is important for several reasons.

– Firstly, therapy of the parenchymal lung disease may be possible.

– Secondly, unlike primary spontaneous pneumothorax, patients with secondary air

leaks are not candidates for early discharge and require inpatient observation.

– Finally, all but the smallest (defined as apical or less than 1 cm in depth) secondary

pneumothoraxes require treatment, even when symptoms are minimal.

– Apical subpleural bullae is seen up to 15% in presence of PTX.

B- CT

* Is the gold standard in diagnostic of PNO.

* CT has increased sensitivity for pneumothorax but is not necessary for the diagnosis of pneumothorax

* However, it can be useful in particular situations, for problem solving; particularly in severe emphysema.

– It may be necessary to diagnose pneumothorax in critically ill patients, in trauma, in whom upright or decubitus films are not possible. The main indication for computed tomography in this clinical setting is to distinguish an emphysematous bulla from a pneumothorax, which can be difficult on standard radiographs.

– Emphysematous bullae may also mimic a loculated pneumothorax, particularly when there is a background of chronic lung disease. Sometimes internal lung markings are visible in a bulla

using a bright light. If there is clinical doubt in a patient with symptoms then computed tomography is helpful.

* High resolution computed tomography may also be helpful for Evaluation of underlying lung parenchyma when underlying parenchymal lung disease is suspected but not clearly identified or characterised by a chest radiograph.

– In presumed Spontaneous primary pneumothorax, it may help to identify Frequent paraseptal &/or centrilobular emphysema. Pleural blebs are indistinguishable from subpleural bullae. CT demonstrates focal areas of emphysema in more than 80% of patients with spontaneous pneumothorax, even in lifelong nonsmokers ((Mitlehner & al in Medscape) . These areas are situated predominantly in the peripheral regions of the apex of the upper lobes. In most patients with primary spontaneous pneumothorax (Mitlehner & al in Medscape), the abnormal findings consisted of a few localized areas of emphysema (n < 5) measuring less than 2 cm in diameter.

– and in secondary pneumothorax it can help to identify most of the causes listed above.

– Contralateral disease commonly identified : Important for operative planning

* CT scanning may prove helpful in predicting the rate of recurrence in patients with spontaneous pneumothorax. It was found (Mitlehner & al reported by Fahad M AlHameed ; Medscape) that patients with larger or more numerous blebs, as demonstrated on thoracic CT, are more likely to experience recurrences.

* In critical care and in patients with severe ARDS (ARDS & PNO) , CT Scan identifie additional loculated air collections not seen with traditional radiography (Boland and associates) ( Bolland et & in Loculated Pneumothorax: A Special Challenge In Critical Care) .

CT scan in patients with ARDS (ARDS and PNO)

. can reveal a variety of abnormalities, such as ground-glass opacification, consolidation, interstitial thickening, evidence of fibrosis and pulmonary cysts.

• Chest CT is helpful in understanding the extent of the underlying lung parenchyma distraction and is quite more sensitive in identifying pneumomediastinum and pneumothorax, which are frequently observed in patients with ARDS .

• In a study of 74 ARDS patients who underwent a chest-CT, 32% of all patients presented a loculated pneumothorax (mostly anteromedial) and 30% had pulmonary air cysts (always multiple and mostly bilateral) (Tagliabue M,et & in Eirini Terzi1 et&)

* Cross sectional imaging guidance is occasionally necessary for drainage of loculated pneumothoraxes in difficult locations. and

Extrapleural or intrapulmonary catheter placement is readily seen on computed tomography.

Part Three

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.

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 .

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F2/

– 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.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F3/

* ‘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.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F4/

* 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’.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F5/

‘ stratosphere Sign ’ = barcode Sign

* 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.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F6/

– 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.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F7/

‘Lung point sign.’ (Right) B-mode depicting the lung point: Sliding lung touching the

chest wall. (Left) The ‘seashore sign’ (white arrow) and the ‘stratosphere sign’ (dotted

arrow) as the lung intermittently contacts the chest wall.

* 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.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161/figure/F8/

– 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.

Part Four

V- Diagnosis

* The diagnosis of PNO is suspected in stable patients with dyspnea or pleuritic chest pain and is confirmed with upright inspiratory chest x-ray. Radiolucent air and the absence of lung markings juxtaposed between a shrunken lobe or lung and the parietal pleura are diagnostic of pneumothorax.

– Tracheal deviation and mediastinal shift occur with large pneumothoraces.

* Small pneumothoraces (eg, < 10%) are sometimes overlooked on chest x-ray. In patients with possible pneumothorax, lung markings should be traced to the edge of the pleura on chest x-ray. Conditions that mimic pneumothorax radiographically include emphysematous bullae, skinfolds, folded bed sheets, and overlap of stomach or bowel markings on lung fields. -Ultrasonography (done at the bedside during initial resuscitation) and CT are more sensitive for small pneumothoraces than chest x-ray.

* Traumatic PNO: Diagnosis is usually made by chest x-ray. Ultrasonography (done at the bedside during initial resuscitation) and CT are more sensitive for small pneumothoraces than chest x-ray.

* The size of the pneumothorax, stated as percent of the hemithorax that is vacant, can be estimated by x-ray findings. The numerical size is valuable mainly for quantifying progression and resolution rather than for determining prognosis.

* Open PNO: The diagnosis is made clinically and requires inspecting the entire chest wall surface.

* In critical care and in patients with severe ARDS (ARDS & PNO) , Patients with pneumothorax did not have the traditional clinical and radiologic signs and the most repeatable finding may be a subtle drop in oxygenation measurements without another obvious cause

(Loculated Pneumothorax: A Special Challenge In Critical Care) .

The diagnosis of pneumothorax in critical illness is made from the history and examination of the patient and confirmed, where possible, by radiological investigation. The factors that are important in the history relate to the underlying disease process and any potential for iatrogenic pneumothorax .

The early and accurate diagnosis of pneumothorax in ARDS patients is mandatory since this complication carries an increased mortality. Furthermore, small pneumothoraces in these patients can cause severe hemodynamic or pulmonary compromise. This is the reason why pneumothorax must always be suspected in any patient with ARDS who experiences an acute worsening in respiratory function, accompanied with dyspnea and hypoxemia, which is usually unresponded to oxygen therapy.

– Portable chest X-ray is the first diagnostic evaluation imaging being used and the procedure of choice for the documentation of lung underlying pathology or the presents of lines, tubes or devices. Nevertheless, often exhibits diagnostic disadvantages, taking into account that

pneumothoraces in ARDS patients may have unusual, as well as subtle features and small sized pneumothoraces or loculated pneumothoraces, can be missed on chest X-ray. Furthermore, other types of air leaks, such as pneumomediastinum and interstitial pulmonary emphysema,

may be more difficulty observed by chest radiographs .

– Cases have been described in medical literature, referring to patients presenting clinical deterioration but unchanged chest X-ray and functioning chest drains (Acute respiratory distress syndrome and pneumothorax; ref 14). This is the reason why, especially in patients under mechanical ventilation, serial and daily chest radiographs are necessary in the evaluation of underlying lung pathology.

– There for, if a pneumothorax is suspected and is unrevealed on chest X-ray, a more specific diagnostic imaging like chest-computed tomography (CT) is necessary. CT scan in patients with ARDS, as explained above , can reveal a variety of abnormalities , is helpful in understanding the extent of the underlying lung parenchyma distraction and is quite more sensitive in identifying pneumomediastinum andpneumothorax, which are frequently observed in patients with ARDS.

– Nevertheless, chest-CT evaluation is seldom employed in patients with ARDS, especially patients with severe respiratory failure under mechanical ventilation, mostly due to problems concerning the transfer and monitoring of these critically ill patients.

– Due to these technical difficulties of chest-CT, an essential diagnostic method in critically ill patient gaining respect is lung-ultrasonography, a relatively easy to perform, portable and inexpensive diagnostic imaging. 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 .

– In the same setting, Loculated pneumothorax provides only subtle clinical clues. The only clinical evidence may be deteriorating oxygenation without another obvious cause. US findings may be equivocal . The abscence of lung sliding may be caused by pno but it has others causes as well . The presence of Lung Sliding indicates that there is no PNO but alone doen’t exclude the diagnostic, while the abscence of lung sliding only indicates that there may be one ( because it has others causes as well). Scan the entire chest for B lines. (Clinical chest US: from the ICU to the bronchoscopic suite).

PNO that is not in immediate contact with the chest wall will not be identified on US ( e.g. Loculated PNO against medistinum).

Be prepared for chest CT scans if ever Lung US is inconclusive for this hard-to-catch complication of mechanical ventilation in patients with ARDS.

Right basilar tension pneumothorax in 19-year-old man with acute respiratory distress syndrome (ARDS) caused by severe trauma.

A, Chest radiograph shows right basilar pneumothorax (arrowheads) that caused tension and developed despite two ipsilateral surgical chesttubes. Note two contralateral

surgical chesttubes and small pneumomediastinum.

B, CT scan shows basilar pneumothorax (arrows), surgical thoracostomy tube in pleural space (large arrowhead), small pneumomediastinum, and diffuse changes of

ARDS in lungs. Fine needle (small arrowheads) as localizer has been inserted anteriorly. Note anterior left surgical chest tube.

C, CT scan obtained immediately after insertion of CT-guided 14-French chesttube (arrowhead) that resulted in evacuation of air. Partial resolution of right pneumothorax and lung reexpansion is shown. CT-guided catheter is located in subpulmonic pleural space between lung and dome of liver.

D, Follow-up chest radiograph obtained after drainage shows CT-guided catheter (arrowheads) in place. Note significant resolution of right pneumothorax. Heart has shifted back to normal position with relief of tension.

Bilateral anteromedial pneumothoraces in 19-year-old man with acute respiratory distress

syndrome (ARDS) caused by pneumococcal pneumonia and septicemia.

A, Chest radiograph shows bilateral anteromedial pneumothoraces (arrowheads) that developed

despite presence of bilateral large-bore surgical thoracostomy tubes.

B, Localizing CT scan obtained just before drainage shows bilateral anteromedial pneumothoraces

(arrowheads) and bilateral diffuse parenchymal infiltrates of ARDS and pneumonia.

C, After insertion of bilateral catheters (arrowheads) under CT guidance, chest radiograph

shows that both pneumothoraces have resolved and patient’s condition has improved.

* Tension pneumothorax is a clinical diagnosis, not a radiographic diagnosis, because the respiratory and hemodynamic consequences of tension pneumothorax do not have radiographic equivalents in many circumstances. Radiographic signs of tension (mediastinal shift, inversion of diaphragm, enlargement of affected hemithorax) can occur in the absence of adverse physiologic effects, and the physiologic effects of pleural tension may be present without radiographic signs of tension ( critically ill p.) .

– In ARDS, the diseased noncompliant lung may not collapse in the presence of a pneumothorax, and the controralateral lung may be too stiff to allow mediastinal shift. Thus, tension pneumothorax in ARDS can present as a loculated paracardiac or subpulmonic air collection with little or no mediastinal shift and only slight changes of the cardiac contour.

– Treatment should not be delayed pending radiographic confirmation. Although cardiac tamponade also can cause hypotension, neck vein distention, and sometimes respiratory distress, tension pneumothorax can be differentiated clinically by its unilateral absence of breath sounds and hyperresonance to percussion.

– Although non-specific, the association of respiratory and haemodynamic signs found with a tension pneumothorax are a medical emergency. Severe haemodynamic compromise will require urgent needle decompression of the pneumothorax before its diagnosis being confirmed radiologically. Fortunately this situation is uncommon and there is frequently time for radiological investigations to help establish the diagnosis of a simple pneumothorax.

VI- Significant Points

* A large pneumothorax is radiographically defined as one with > 2 cm from pleural surface to lung edge; this is an objective indication for drainage

* Don’t wait for a radiograph if there are clinical signs of a tension pneumothorax.

Tension pneumothorax is a medical emergency and may require immediate needle decompression before radiological investigation.

– Treat the patient not the radiograph. Don’t act on a radiographic appearance if it does not fit the clinical picture. Get an expert opinion on the radiograph first.

* Skin folds, companion shadows, the scapula, and previous lung surgery or chest drain placement may all mimic pneumothoraxes on XRay Chest.

* In the supine patient, pneumothoraxes are best seen at the lung bases and adjacent to the heart.

The “deep sulcus sign” describes a costophrenic angle that extends more inferiorly than

usual as a result of air lying in the costophrenic angle. The liver appears more radiolucent than

usual due to air lying anteriorly in the costophrenic angle, and on the left side, air will

outline the medial aspect of the hemidiaphragm under the heart.

* What other radiological investigations may be used to confirm the diagnosis of PNO in acute traumatic setting and in critically ill patients?

– A radiograph with the patient in a lateral decubitus position, with the affected side uppermost, can be helpful in demonstrating a lung edge.

– In patients well enough to be transported, thoracic computed tomography can be helpful in locating the position of a pneumothorax and accurately siting a chest drain.

– US and CT are more sensitive than Chest X-Ray Radiography in detection PNO. CT is the gold standard. US is done at the bedside during initial resuscitation of trauma patient and in critically ill patient in ICU.

– The early and accurate diagnosis of pneumothorax in ARDS patients is mandatory since this complication carries an increased mortality. Portable chest X-ray is the first diagnostic evaluation imaging. If a pneumothorax is suspected and is unrevealed on chest X-ray, Lung USG is now an alternative method to Chest CT mostly due to the cumbersome nature of this technique in critically ill patients.

* The negative predictive value of Chest US for lung sliding is reported as 99.2–100%, indicating that the presence of sliding effectively rules out a pneumothorax. For some authors,

lung sliding ALONE does not exclude PNO and scanning of the entire anterior chest for B-Lines is mandatory (Ultrasonography in the ICU: Practical Applications).

– However, the absence of lung sliding does not necessarily indicate that a pneumothorax is present. In fact, Lung sliding is abolished in a variety of conditions other than pneumothorax.

– Lung Sliding and B lines are not present on a patient with PNO. M Mode can help differenciate between a seashore sign or Stratosphere or bar code signs ( SeaShore = no PNO).

* Blind chest drain placement into a loculated pneumothorax may lead to an iatrogenic air leak

from direct trauma to the pleura and worsening the patient’s clinical condition.

* An immediate post-treatment radiograph is essential to detect complications and ensure a

satisfactory drain position

* A chest drain apparently well positioned on frontal radiograph may be lying in the soft tissues, in a lung fissure, or within the substance of the lung.

VII- References

1– Fahad M AlHameed, MD, AmBIM, FCCP, FRCPC; Chief Editor: Eugene C Lin, MD. Pneumothorax Imaging: Overview, Radiography, Computed Tomography, in emedecine / Medscape, Updated: Oct 04, 2015, (Page consulted February 12, 2016).

[http://emedicine.medscape.com/article/360796-overview#showall]

2-Patricia Carroll, RN,C, CEN, RRT, MS Loculated Pneumothorax: A Special Challenge In Critical Care., in Clinical Update for the Professional Nurse, September 2000. Clinical Update is an educational newsletter provided by Atrium Medical Corporation.

[http://www.atriummed.com/en/chest_drainage/Clinical%20Updates/ClinicalUpdateSept00.pdf]

3– Chon KS, vanSonnenberg E, D’Agostino HB, O’Laoide RM, Colt HG, Hart E: CT- guided catheter drainage of loculated thoracic air collections in mechanically ventilated patients with acute respiratory distress syndrome. American Journal of Roentgenology 1999;173(5):1345-1350, in PubMed – indexed for MEDLINE , PMID: 10541116. [http://www.ajronline.org/doi/abs/10.2214/ajr.173.5.10541116]

[http://learningradiology.com/new/quizzes/quiz0004/index0004.htm].

[http://radiopaedia.org/articles/pneumothorax-ultrasound. Page consulted February 12, 2016. ]

6- Terrance Healey, MD– Pneumothorax, Primary Spontaneous, in

Chest > Diagnosis > Pleural Diseases > Pneumothorax. (Page consulted February 12, 2016).

[https://my.statdx.com/document/pneumothorax-primary-spontaneous/eb1b4e8a-d718-45c8-9935-34da254c9af3?searchTerm=Pneumothorax,%20Primary%20Spontaneous]

7– Lubna F Husain, Laura Hagopian, Derek Wayman, William E Baker, and Kristin A Carmody: 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).

[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3299161]

8- Jain, Arpana (et al.). Thoracic Ultrasonography in the Critically Ill, in Paula Ferrada (Ed.), Ultrasonography in the ICU: Practical Applications Pages 37-52, © 2015 Springer International Publishing, eBook ISBN 978-3-319-11876-5, in google Books, (Page consulted February 12, 2016).

[https://books.google.com.lb/books?id=9Fx1CQAAQBAJ&pg=PA51&lpg=PA51&dq=loculated+pneumothorax+and+ultrasonography&source=bl&ots=re2jhh0 lu&sig=lOXixQ68hsRD1ZegQCQSpQ9YTs&hl=fr&sa=X&ved=0ahUKEwj566y21uzKAhWDthoKHauLDO0Q6AEIVjAI#v=onepage&q=loculated%20pneumothorax%20and%20ultrasonography&f=false].

9- Arun Nagdev, MD, and Michael Murphy, MD: Focus On: Ultrasound Detection of Traumatic Anterior Pneumothorax, in Copyright © 2014 American College of Emergency Physicians American website, December 2008. (Page consulted February 12, 2016).

[http://www.acep.org/Clinical—Practice-Management/Focus-On–Ultrasound-Detection-of-Traumatic-Anterior-Pneumothorax ]

10- A R O’Connor, W E Morgan. Radiological review of pneumothorax, in BMJ 2005;330:1493–7, in PMC free articles, PMCID: PMC558461

[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC558461]

11- Pneumothorax From Wikipedia, the free encyclopedia. Page was last modified on 16 January 2016, at 22:13, (page consulted February 12, 2016).

[https://en.wikipedia.org/wiki/Pneumothorax]

13- Richard W. Light, MD. Pneumothorax in Merck Manual, Professionnal Version, [http://www.merckmanuals.com/professional/pulmonary-disorders/mediastinal-and-pleural-disorders/pneumothorax], Last full review/revision September 2014, ( page consulted February 12, 2016).

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