Dr WALIF CHBEIR
* 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.
PNO is air in the pleural space causing partial or complete lung collapse.
* 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.
– Chronic obstructive pulmonary disease
– Cystic fibrosis
– Pneumonia: Pneumocystis jirovecii infection / Tuberculosis /
Bacterial pneumonia.( Cavitary or Necrotizing) .
— 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 .
– Connective tissue disorders: Ankylosing spondylitis , Ehlers-
Danlos syndrome, Marfan syndrome, Polymyositis and dermatomyositis, RA,
– 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
– In patients with penetrating wounds that traverse the mediastinum,or with severe
trauma, pneumothorax may be caused by disruption of the tracheobronchial tree. Air
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
– 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
– 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
* 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
– Air from the pneumothorax may enter the soft tissues of the chest and/or neck
emphysema), or mediastinum (pneumomediastinum).
– Patients commonly have pleuritic chest pain, dyspnea, tachypnea, and
– Breath sounds may be diminished and the affected hemithorax hyperresonant to
percussion—mainly with larger pneumothoraces. However, these findings are not
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
– 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
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
into the pleural space but not out of it (a one-way valve). As a result, air accumulates
compresses the lung, eventually shifting the mediastinum, compressing the
lung, and increasing intrathoracic pressure enough to decrease venous return to the
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
– 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
. 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,
pneumothorax can cause severe hypotension, and open pneumothorax can
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.
* 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.
* 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.
* 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
– 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
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
– 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
– 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 .
– 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
– 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.
* ‘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.
* 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’.
‘ 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
3- A lines are other important thoracic artifacts that can help in the diagnosis of a
– These are also reverberation artifacts appearing as equally spaced repetitive
horizontal hyperechoic lines reflecting off of the pleura. The space in between each A
corresponds to the same distance between the skin surface and the parietal pleura.
– 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.
‘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
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
as larger pneumothoraces are more likely to require thoracostomy.
* The ‘Power Slide’ refers to the use of power (angiography) Doppler to help identify
– 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
– This technique can be helpful in cases of subtle sliding when direct visualization may
– 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
prevent artifact and erroneous color flow over the pleural line, when sliding is actually
* 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.
* 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
* 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
* 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).
* 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
– 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) .
* Thoracic sonography for the detection of pneumothorax has become a well
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
* 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
* Bedside ultrasound obviates the need for patient transport in unstable situations, it
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
– 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.
* 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.
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