The lungs exist inside the chest cavity, which is a hollow space. Air is drawn into the lungs by a powerful abdominal muscle called the diaphragm which separates the chest cavity from the lower internal organs. The pleural cavity is the region between the chest wall and the lungs. If air enters the pleural cavity, either from the outside or from the lung, the lung collapses and it becomes mechanically impossible for the injured person to breathe, even with a clear airway.
If a piece of tissue forms a one-way valve that allows air to enter the pleural cavity from the lung but not to escape, overpressure can build up with every breath; this is known as tension pneumothorax. It may lead to severe shortness of breath as well as circulatory collapse, both life-threatening conditions.
Small pneumothoraces often resolve spontaneously and may require no other treatment than clinical observation. A large pneumothorax or tension pneumothorax can be a medical emergency.
Causes of pneumothorax
Common causes of pneumothorax are a penetrating chest injurytrauma, atmospheric overpressure, and preexisting lung disease; a pneumothorax may also occur spontaneously without apparent cause. A tension pneumothorax is caused by interior injury to the lung which does not breach the chest wall, or by an improperly applied dressing for a penetrating chest wound. Rarely it may result from lung illnesses such as advanced pneumonia or lung cancer.
Diagnosis of pneumothorax
A person with injuries as above is unable to breathe even though they have a clear airway. They may spit or cough up blood. They will turn "blue" and become unconscious. Immediate treatment is required within minutes or the injured person will die. There may be only one wound (an entrance wound) or two (an exit wound as well). Both must be treated.
Treatment of pneumothorax
One standard first aid treatment is to cover the wound with pressure bandage(s) made air-tight with petroleum jelly or clean plastic sheeting. The sterile inside of plastic bandage packaging is good for this purpose; however any airtight material, even the cellophane of a cigarette pack, can be used.
IMPORTANT: do not completely close off the opening. Leave a flap or corner open so that air does not build up in the lungs yet the patient can still breathe.
Any patient with a penetrating chest wound must be closely watched at all times and may develop a tension pneumothorax or other immediately life-threatening respiratory emergency at any moment. Do not leave them alone, even for a moment.
Field Care (for EMTs)
Apply airtight pressure bandage(s) as above. Provide oxygen therapy. Use caution in applying positive pressure ventilation and the use of bag-valve masks; follow local protocols. Intubation may be required, even of a conscious patient. Advanced medical care and immediate evacuation are strongly indicated.
Watch carefully for tension pneumothorax. One paramedic procedure to treat tension pneumothorax is to open a small wound into the chest cavity with a large hollow needle which can be capped or uncapped as required.
DANGER: if in the mountains or evacuating by air (MEDEVAC), consider the effects of change of altitude on the patient. If the patient experiences respiratory distress immediately after a change in altitude, immediately return to the former altitude. This may require a series of short "hops" by helicopter until a roadway is reached for ground ambulance transport.
Immediate surgery to close the hole in the chest wall and/or lung. Supportive therapy including mechanical ventilation. A long period of hospitalization is likely, including respiratory therapy.