Pneumothorax Flashcards
Define pneumothorax.
Pneumothorax occurs when air gains access to, and accumulates in, the pleural space.
How common is pneumothorax?
- Incidence of PSP in UK is 24/100,000 in men and 10/100,000 in women
- Men <20yrs and ~ 60yrs,
- Women ~30-34yrs and ~60yrs.
- Pneumothoraces are second most common chest trauma injury (following rib fractures).
What are the risk factors for spontaneous pneumothorax?
- cigarette smoking
- FH
- male sex
- tall and slender body build
- age <40 years
- underlying lung conditions e.g. acute severe asthma, COPD, tuberculosis, PCP, cystic fibrosis
- Structural abnormality e.g. Marfan, Ehlers-Danlos
- Menstruation → catamenial pneumothorax within 72hrs of menstruation; rare.
What are the key presenting symptoms of pneumothorax?
- Chest pain - on same side as pneumothorax
- Dyspnoea - degree depends on size of pneumothorax and presence and severity of pre-existing lung disease
- Extreme breathlessness (depending on size of lesion)
- Some may have no symptoms
What are the findings on physical examination of someone with pneumothorax?
Pulse exam:
- Tachycardia and pulsus paradoxicus (pulse slows on inspiration)*
- Hypotension may occur and JVP may be raised
Neck: Sometimes trachea is shifted to contralateral side in tension pneumothorax
Chest exam:
- Hyperexpanded ipsilateral hemithorax
- Hyper-resonant ipsilateral hemithorax
- Ipsilateral absent or diminished breath sounds
What is the difference between pulsus paradoxicus and sinus arrhythmia?
Pulsus paradoxicus occurs when the pulse slows on inspiration.
This is the opposite to sinus arrhythmia where there is a slight acceleration of the pulse with inspiration.
Explain the aetiology of pneumothorax.
- Pneumothorax = air in pleural space.
- Normally: alveolar pressure> intrapleural pressure and atmospheric pressure>intrapleural pressure.
- If a communication develops between an alveolus and the pleural space, or between the atmosphere and the pleural space, gases will follow the pressure gradient and flow into the pleural space
- Gases follow the pressure gradient.
- The thoracic cavity enlarges and the lung becomes smaller when a pneumothorax develops.
Tension pneumothorax = intrapleural>atmospheric - results from a ball valve mechanism that promotes inspiratory accumulation of pleural gases.
Catamenial pneumothorax= mechanisms unknown; intrathoracic endometriosis –> visceral pleural erosions –> pneumothorax.
Why does being tall predispose to formation of pneumothorax?
Alveoli at the lung apex are subjected to greater mean distending pressure in taller patients –> subpleural blebs + other abnormalities.
What investigations would you do for a pneumothorax? What would each show?
- CXR
- CT - more sensitive than CXR. Visceral pleural line is easily identified and atelectasis* of the lung can be seen. May show secondary causes.
- Chest ultrasound - absent lung sliding. Useful when PA CXR cannot be obtained.
- Bronchoscopy (in the setting of pneumothorax ex vacuo) –> direct visualisation of endobronchial obstruction
When would you do bronchoscopy to investigate a pneumothorax?
In the setting of pneumothorax ex vacuo because it gives direct visualisation of endobronchial obstruction.
What is pneumothorax ex vacuo?
- Rare - seen in atelectasis
- Rapid collapse of lung –> rapid decrease in intrapleural pressure –> increased -ve intrapleural pressure causes gaseous nitrogen molecules to migrate from the pulmonary capillaries into the pleural space.
How do you classify pneumothoraces?
-
Spontaneous pneumothorax (no preceding trauma/precipitating event)
- primary - no pulmonary disease
- secondary - complication of underlying pulmonary disease
- Traumatic pneumothorax (by penetrating or blunt injury to chest, or iatrogenic)
- Tension pneumothorax - intrapleural>atmospheric
- Pneumothorax ex vacuo
List some iatrogenic causes of pneumothorax.
- Transcutaneous needle aspiration of lung lesions
- Thoracentesis
- Endoscopic transbronchial biopsy
- Central venous catheter placement
- Barotrauma from mechanical ventilation
What are the complications of pneumothorax and its management?
Re-expansion pulmonary oedema - if large and present for >72 hours. May also develop in contralateral lung.
Talc pleurodesis-related ARDS
- Pleurodesis –> systemic inflammatory response which can play a role in ARDS pathogenesis.
- But talc pleurodesis is safe when size-calibrated talc is used in recommended dosages.
How do you manage a spontaneous pneumothorax?
Primary:
- >2cm or breathless → aspirate with 6-18G cannula (<2.5L)
- <2cm discharge and review in 2-4weeks
Secondary :
- >2cm or breathless → chest drain 8-14Fr and admit
- 1-2cm → aspirate 16-18G cannula (<2.5L)
- <1cm → admit and observe for 24hrs
What is the procedure with chest drains?
Inserted by Seldinger technique
Once inserted in triangle of safety 5th ICS midaxillary line do CXR to confirm position
Keep underwater bottle upright and drain always below the insertion site
Give appropriate pain relief - NSAID +/- codeine
