Pneumothorax Flashcards
What is a pneumothorax?
an abnormal collection of air in the pleural space
(between the lung and the chest wall)
How can pneumothorax be categorised?
they can be primary or secondary
primary - there is no underlying lung disease
secondary - there was already underlying lung disease (such as COPD)
they can then be seperately classified as spontaneous or traumatic
What is a tension pneumothorax and how does it develop?
the majority of cases of spontaneous pneumothorax are minor and will self resolve
sometimes, a one way valve can form, allowing more and more air into the pleural space
this is a tension pneumothorax and it is a medical emergency
What is a primary spontaneous pneumothorax (PSP) usually the result of?
Who is most commonly affected?
usually the result of rupture of a pleural “bleb”
the bleb is often from a congenital defect in the tissue of the alveolar wall
blebs are more common in tall young men
PSPs are more common in men (M:F is 2.5:1)
What is the recurrence rate for PSPs?
What age tend to be affected?
recurrence rate is 25-50% and they usually recur within the first year
patients affected are typically in their 20s
PSPs are rare after the age of 40
What are the risk factors for PSPs?
In what % of cases does tension pneumothorax occur?
-
smoking (including cannabis)
- 90% of cases occur in smokers
- risk is proportional to the amount smoked
-
family history
- 25% of cases have an associated family history
- Marfan syndrome
- homocystinurea
a tension pneumothorax occurs in 1-2% of cases
What are the possible causes of secondary pneumothorax?
- COPD
- cystic fibrosis
- lung malignancy
- pneumonia
- tuberculosis
What are the differences in the ways that primary and secondary pneumothoraces present?
they are often very similar acute events
symptoms are often more severe in secondary pneumothorax
this is presumably due to the reduced reparatory reserve seen in underlying lung disease
What symptoms are associated with pneumothorax?
How quickly do they present?
sudden onset of shortness of breath and pleuritic chest pain (usually on the side of the pneumothorax)
symptoms are often proportional to the size of the pneumothorax
symptoms typically develop at rest
What signs may be found on clinical examination in pneumothorax?
- reduced breath sounds on the affected side
- hyperresonance to percussion on affected side
-
hypoxia
- hypercapnia is NOT usually present
What is a simple pneumothorax?
How can it be identified on chest X-ray?
air in the pleural space, but the volume is NOT increasing
on CXR the trachea is not deviated
lung collapse may be visible (sometimes subtle with decreased vascular markings around the outer lung field)
What is a tension pneumothorax?
What does it look like on chest X ray?
air in the pleural space, and the volume continuing to increase
this is typically due to the formation of a one-way valve that allows air into the pleural space on inspiration, but not out again on expiration
on CXR the trachea may be deviated away from the side of the pneumothorax
lung collapse is likely to be more obvious
Why is tension pneumothorax a medical emergency?
it is life threatening
it rapidly increases intra-thoracic pressure
this reduces venous return to the heart and causes cardiac arrest if not treated quickly
What are the clinical features of a tension pneumothorax?
- pleuritic chest pain
- breathlessness
- tracheal deviation
- reduced breath sounds in the affected area and hyper-resonant on percussion
these features may not be present - and when they are present they are a very late sign
How can a tension pneumothorax be differentiated from a simple pneumothorax?
- a tension pneumothorax has worsening clinical signs and symptoms, whereas a simple pneumothorax is stable
- there is tracheal deviation in a tension pneumothorax
- a tension pneumothorax is haemodynamically unstable
- hypotensive
- tachycardic
- elevated respiratory rate
What are potential complications of pneumothorax?
compression of the mediastinum leads to decreased cardiac output as the heart is compressed
this leads to increased heart rate, jugular vein distension and cardiac arrest
How is pneumothorax typically diagnosed?
it is often a clinical diagnosis
tension pneumothorax should be a clinical diagnosis as there is no time to wait for an X-ray
called “the x-ray you never want to see” as it should have been diagnosed and treated beforehand
What does a typical pneumothorax look like on chest X-ray?
- typically they are small
- they often appear as a “rim” of air around the lung
- it is often possible to see a white line which represents the edge of the normal lung tissue
- there are no vascular lung markings externally to this
What does a large pneumothorax look like on chest X-ray?
- they tend to be more obvious
- there is usually a clearly collapsed lung and a large proportion of the hemithorax with no vascular margins
What sign should be looked for on chest X-ray to differentiate a tension pneumothorax from a simple pneumothorax?
mediastinal shift indicates the presence of a pneumothorax
the absence of mediastinal shift does not exclude tension pneumothorax and diagnosis is often clinical (signs of haemodynamic instability) as it is often not possible to tell the difference on X-ray findings alone
How can primary and secondary pneumothoraxes be differentiated on X-ray?
check for underlying lung disease to differentiate between a primary and secondary pneumothorax
What are the indications for CT investigation?
- evidence of underlying lung disease on CXR
- uncertain diagnosis
- not routinely indicated
What tends to mimic a pneumothorax?
Why is further investigation needed?
a large bleb / emphysematous bullae may mimic a pneumothorax
this makes diagnosis unclear so a CT scan should be considered
if the diagnosis is uncertain and there is NOT a pneumothorax, you may cause one by attempting a decompression
How can you identify a tension pneumothorax on chest X-ray?
- absent lung markings
- collapsed (left) lung
- mediastinal shift (to the right)
