Mystery Writer's Guide to Forensic Science - Pneumothorax (The Colapsed Lung)

There are two types of pneumothorax: Tension and Simple.

Simple pneumothorax

• In a simple pneumothorax, there is usually only partial collapse of a lung. The pressure built up in the lung cavity is not enough to cause cardiovascular dysfunction.
  
  
• The collapsed lung may be severe enough to lead to decreased amounts of oxygen in the blood, causing the patient to feel short of breath.
  
  
• This type of pneumothorax can be small and "stable", and not require emergency treatment. However, the pneumothorax may slowly or rapidly progress to cause more severe cardiovascular impairment and may often need to be monitored. 

Tension pneumothorax

• This refers to a condition in which air builds up under pressure and usually totally collapses one or both of the lungs. This causes severe dysfunction of the cardiovascular system.
  
  
• The pressure built up in the lung cavity slows or stops the return of blood to the heart from the veins. Because the heart has less blood available to pump into the main arteries, blood pressure drops, and other vital organs are rapidly affected.
  
  
• In an affected person does not receive emergency treatment, death may result.

Signs and Symptoms:

• Decreased or absent breath sounds on the affected side
• Unequal chest rise
• Shortness of breath
• Rapid breathing
• Rapid heart rate
• Low blood pressure
• Hypoxia (deficiency in the amount of oxygen reaching the tissues)
• Pale, cool, clammy skin
• Subcutaneous emphysema (air trapped beneath the skin)
• Bluish skin
• Jugular venous distension (enlarged jugular veins; late sign)

With Tension Pneumothorax, air gets trapped between the lung and chest cavity. Although the lung can expel air into the chest cavity, it can NOT go back into the lung. So, the pressure begins to build causing further collapse of the affected lung, good lung, and pressure upon the heart. Every breath taken only furthers the problem. This is often when you see on TV the hero jabs a large needle into the chest (between the ribs) and a gush of air signals success. Miraculously, the patient recovers from near death to near normal health in a matter of seconds!

Sources: emedicine.com, wikipedia, Trauma.org