A stab wound to the apex of the pleura, located about 1 inch (2.5cm) above the clavicle, by a surgeon's knife or an anaesthesiologists needle can cause pneumothorax.

Pneumothorax is the presence of free air or gas in the pleural cavity

Types of pneumothorax include open pneumothorax, spontaneous pneumothorax, and tension pneumothorax.

Collapse of ipsilateral lung due to pressure change and disruption of surface tension.

In pneumothorax, there is a potential for mediastinal shifts

- positive pressure introduced into the lungs from the atmosphere will cause the lungs to collapse.
- in pneumothorax, the pleural cavity is pushed in, causing the lung to collapse inwards, towards the middle.
- b/c there are two lungs, each in their own pleural cavity, one collapsing doesn't preclude the other from collapsing.  In bulls or oxen, their chest cavity is in a single pleural cavity, thus, if they are pierced with a spear, the whole chest cavity collapses from positive pressure from the external atmosphere.
- Symptoms include being breathless, absence of air, decreased air entry, too much air in the lungs, fall of blood pressure, tachycardia, lower temperature, increased respiration rate.

- Entry of air into a pleural cavity causing lung collapse causing lung collapse.
- Spontaneous pneumothorax  is partial collapse of the lung due to a rupture on the lung surface or due to a punctured lung.
- Open pneumothorax is due to a stab wound of the thoracic wall which pierce the parietal pleura so that the pleural cavity is open to the outside air via the lung or through the chest wall; also called blowing or sucking wound.
- Tension (vulvular) pneumothorax is when air builds up on the wounded side and pushes (shifts) the mediastinum toward the opposite side because air enters the affected pleural cavity during inspiration and is trapped during expiration; a dangerous situation (a medical emergency).  One lung is collapsed and the other is compressed by the shifted mediastinum
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Open Pneumothorax
- For inspiration: Air enters pleural cavity through open, sucking chest wound.  Negative pleural pressure lost, permitting collapse of ipsilateral lung and reducing venous return to the heart.  Mediastinum shifts, compressing opposite lung.
- As chest wall contracts , air expelled from pleural cavity via wound. Mediastinum shifts to affected side and mediastinal flutter further impairs venous return by distortion of venae cavae.
- Patient is often cyanotic and in severe respiratory distress or shock.  Immediate closure of sucking wound imperative, preferably petrolatum gauze pad, but if not available, with palm or anything at hand.
- Chest strapped over packing on top of petrolatum gauze.  Thoracostomy tube attached to underwater-seal suction drainage or Heimlich valve may of indicated to promote reexpansion of lung.  Wound debridement may be necessary.  Possible associated hemothorax must also be considered.


Tension Pneumothorax
- Inspiration: Air enters pleural cavity through lung wound or ruptured bleb (or occasionally via penetrating chest wound) with valvelike opening.  Ipsilateral lung collapses and mediastinum shifts to opposite side, compressing contralateral lung and impairing its ventilating capacity.
- Expiration: Intrapleural pressure rises, closing valvelike opening, thus preventing escape of pleural air.  Pressure thus progressively increased with each breath.  Mediastinal and tracheal shifts augmented, diaphragm depressed, and venous return impaired by increased pressure and vena caval distortion.
- Clinical manifestations include respiratory distress, cyanosis, tracheal deviation, chest pain, hyperresonance,
- A diagnotic tap with moistened glass syringe is performed.   Plunger pushed out by intrathoracic pressure.
- Therapeutic Manuevers: Incision in 3rd interspace with introduction of thoracostomy tube attached to underwater-seal suction.
- A large-bore needle inserted for emergency relief of intrathoracic pressure.  Finger cot flutter valve,Heimlich valve, or underwater seal should be attached.
- Knowledge of the extent of the lung and pleura is clinically important.  Their lower parts overlap abdominal organs such as the liver, kidney and spleen.  On the apical pleura lie the subclavian vessels and the brachial plexus.  Procedures such as exposure of the  kidney, liver biopsy, and cannulation of the subclavian vein may inadvertently produce a pneumothorax, resulting in collapse of the lung.