TENSION PNEUMOTHORAX

DEFINITION
Air entering the pleural space under pressure, collapsing the lung and causing haemodynamic compromise due to mediastinal shift and obstruction to cardiac inflow, possibly causing death if not promptly treated.

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INCIDENCE
Incidence
Any age.

Risk Factors
Asthma
Emphysema
IPPV
CT disorders eg Marfans.

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AETIOLOGY

Neonates

Spontaneous, even without IPPV.
Adults
Chest trauma with or without rib #s.
- most commonly mechanical PPV in a pt with a visceral pleural injury.
- can follow a simple pneumothorax where a parenchymal lung injury has failed to heal.
- occasionally follows a chest wall injury if incorrectly covered with occlusive dressings or creating a flap/valve.
- may occur in markedly displaced T-spine #s.
Any procedure involving the chest can induce one.

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BIOLOGICAL BEHAVIOUR

Pathogenesis

Air enters the pleural space through a defect.
The opening acts as a one way valve.
- air enters as resp effort draws a negative pressure
- but cannot escape during expiration.
Harder breathing, coughing or IPPV worsens tension.

Pathophysiology
Lung collapse causes hypoxaemia as for any pneumothorax.
- as pressure rises, mediastinal shift occurs.
--> contralateral lung is compressed.
Shift may occlude the IVC at the diaphragm.
- and SVC above heart
--> venous return is impaired --> decreased preload --> CO diminishes.
--> cardiovascular collapse.


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MANIFESTATIONS

i) Severe Respiratory Arrest
ii) Shock


Symptoms

Chest pain, often sudden and unilateral.
Air hunger.
Deteriorates rapidly
Loses consciousness
Turns blue
Appears to be dying (and is)

Signs
Observe
Progressively worsening respiratory distress
Distended neck veins
Cyanosis / hypoxia
Palpate
Shock, with hypotension & tachycardia
- become bradycardic if near death.
Tracheal deviation
Subcutaneous emphysema
Percussion
Hyper-resonance
Auscultate
Decreased / absent breath sounds on side of pneumothorax

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INVESTIGATIONS

Tension pneumothorax is a clinical diagnosis.
There should never be a CXR of a tension pneumo.
Radiology
Mediastinal displacement, absent lung marking, lung border collapsed.

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MANAGEMENT

Needle Decompression

- converts tension to simple.
- commonly done by paramedics.
However, finger thoracostomy probably better in ED / resus context.

Chest Tube Insertion
As soon as able.
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