A lung embolus (pulmonary embolism) occurs when a blood vessel supplying the lung becomes clogged up by a clot - a lump of coagulated blood.

The clot may have travelled in the bloodstream from a vein in the pelvis, abdomen or in the leg; through the veins of the body, through the heart and into the lung. A damaged heart can also be the cause of these clots.

Signs of a small embolus:

• the most important symptom is breathlessness, which often occurs suddenly and for which there is no other explanation such as an asthma attack.
• you feel a sudden pain in your chest.
• you may cough up blood in your phlegm.
• you start feeling uncomfortable, nervous and anxious.
• in the days that follow you may have a slight fever and feel exhausted but after a while you may feel better and the symptoms may disappear within a couple of weeks.
• as there is a bigger risk of you getting a new embolus after the first, you should see a doctor immediately.
• in virtually all cases you will need preventive medicine because of the chance of a re-occurrence. This means that most people who have had even a small pulmonary embolus need to go to hospital as an emergency to confirm the diagnosis and to start treatment.

Larger emboli in the lungs can be lethal. Unfortunately, attempts to resuscitate a person with a larger embolus rarely succeed.

Signs of larger emboli:

• sudden appearance
• you become pale and break out into a cold sweat
• unconsciousness may follow quickly
• without medical attention, death may occur.