This document provides an overview of pneumothorax (PNO), including its definition, causes, symptoms, diagnosis and complications. It discusses different types of PNO such as primary spontaneous PNO, secondary spontaneous PNO, traumatic PNO, tension PNO and PNO in patients with acute respiratory distress syndrome (ARDS). PNO is caused by air in the pleural space and can range from asymptomatic to life-threatening depending on the type and size. Imaging plays a key role in diagnosis. Complications include recurrence and tension PNO which can impair breathing and circulation.

1. Edited March02,2016
Medical Imaging of PneumoThorax (PNO1)
Dr WALIF CHBEIR
* We searched Medline and google for articles relating to Pneumothorax with focus on
imaging appearances and diagnostic approach.
* Key Words: - Pneumothorax/etiology. - Pneumothorax/radiography.
- Pneumothorax/ultrasonography. - Pneumothorax/diagnosis. - Acute respiratory distress
syndrome (ARDS) - Tension Pneumothorax - intensive care unit (ICU)- mechanical
ventilation. - critical care
* 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

2. - 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.

3. - 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 high-altitude 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.

4. - 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.

5. - 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).

6. - 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.

7. . 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.