A tension pneumothorax is when air builds up inside the chest. So much air builds up that one or both lungs may collapse.  This causes serious breathing problems.  Also, the air in the chest pushes on the heart and other important parts of the body, and causes other serious problems.  If it is not treated quickly, a tension pneumothorax will kill a person.

How does a tension pneumothorax happen?
A tension pneumothorax usually happens because of an injury to the chest. For example, a knife or gunshot wound will cause a hole in a person's chest.  Air then gets sucked in through that hole.  The air starts to build up. It pushes on the lungs.  If the knife or gun has also caused a hole in the person's lung, air will leak out of the lung.  That air will also build up in the chest.  When enough air is pushing on the lung, the lung will collapse.

A tension pneumothorax can also happen because of other kinds of chest injury, like from a car accident or a fall.  When a person gets injured this way, there may not be any hole in his chest.  But inside the body, the person may be bleeding badly.  Instead of air, blood builds up in the chest. It pushes on the lung and makes it collapse.  This is called a hemothorax.

What happens as a tension pneumothorax gets worse?
Once a person's lung collapses, they will have trouble breathing.  As air or blood keeps building up in the chest, the person's symptoms will keep getting worse.

The air or blood in the chest will push against and squeeze the heart.  This can cause serious problems.  If the heart is squeezed too much, it cannot fill with blood very well.  This means it does not have enough blood to pump to the rest of the body.  Every part of the body needs blood to survive.  If the heart cannot pump enough blood to the body, other parts of the body can start to die.

Pressure in the chest can also squeeze the vena cavae, the big veins that bring blood from the body back to the heart.  If the vena cavae are squeezed too tightly, blood will not be able to get into the heart.  This means the heart will not have enough blood to pump to the lungs or the rest of the body.

If a person bleeds enough into their chest, they can go into shock and die from blood loss.

If enough pressure builds up in the chest, the other lung can collapse, too.  If both lungs have collapsed, there will be no way for the person to breathe.

Symptoms
A tension pneumothorax will cause some other symptoms.  For example:
 Mediastinal shift.  This means that everything in the mediastinum - the space between the heart and the lungs - will get pushed to one side by the air or blood in the chest. For example, a medical professional will be able to see that the trachea (windpipe) is pushed to one side.  In medicine, this is called tracheal deviation or tracheal shift.
 Jugular vein distention (JVD).  This means that the big veins in the neck will be filled with blood.  They will look big and full. This happens because blood cannot get to the heart through the vena cavae, because they are being squeezed too hard, so the blood backs up into the veins in the neck (the jugular veins).
 Bulging intercostals.  The muscles between the ribs may get pushed out because of the pressure inside the chest.
 Unilateral breath sounds.  When a medical professional listens to the lungs with a stethoscope, they will be able to hear breath sounds - the sounds of air going in and out of the lungs - only on one side.  They will hear nothing on the side where the lung has collapsed.

Treatment
A tension pneumothorax always needs emergency medical treatment.  If a person may have a tension pneumothorax (or has any bad injury to the chest), 911 or another emergency telephone number should be called right away.  The emergency medical dispatcher will be able to explain how to help the person until an ambulance gets there.

Emergency medical technicians (EMTs) or paramedics may give these treatments for a tension pneumothorax:
 Give the person oxygen
 Put something occlusive over the hole in the chest to keep air from getting through.  Examples of things that can be put over chest wounds are plastic wrap, aluminum foil, a hand with a medical glove on it, or special sticky plastic bandages (called occlusive dressings).  These will keep more air from getting in through the hole in the chest. They also keep even more pressure from building up in the chest.
 Put a hollow needle into the person's chest so air can get out through the needle.  This is called a needle decompression.

At the hospital, a patient with a tension pneumothorax will be given a chest tube.  This is a tube that is placed into the chest so that air or blood can get out and does not build up inside.  If the person has bled a lot into their chest, they may also get blood transfusions.

Related pages
 Pneumothorax
 Lungs

References

Medical emergencies
Respiratory system