Pulmonary embolism is a common clinical picture. Although the statements in various studies differ, it can be assumed that on average about 1 person per 1000 inhabitants is affected by pulmonary embolism in Germany each year – older people more often than younger people. Among hospitalized patients, pulmonary embolism is one of the most common causes of death.
Clogged vessel as cause
The right heart pumps deoxygenated blood from the body into the large and small arteries of the pulmonary circulation. In these, it is carried to the alveoli, where it is reoxygenated.
Sometimes, however, the blood from the body not only brings carbon dioxide to be exhaled, but also flushes in dangerous particles: usually blood clots from a thrombosis in the leg veins, but also – much more rarely – fat, for example after bone surgery, air from an infusion, bacteria, tumor cells or amniotic fluid that enters the maternal circulation during birth. These substances can get stuck and block the corresponding vessel.
If the clot is only in a small artery, it may go unnoticed; if a larger or multiple vessels are affected, it can lead to severe, life-threatening disease.
How exactly does pulmonary embolism develop?
In most people affected, pulmonary embolism stems from a blood clot that has formed in veins in the pelvis or legs. Small particles detach from these clogged blood cells and are carried along with the bloodstream. The veins initially widen and eventually flow into the portal vein, which leads to the right heart. Only in the lungs do the vessels branch out again and become increasingly narrow. Therefore, it is only there that the particles reattach themselves and obstruct the vessel.
Once this process is underway, the blood backs up in front of it, slowing its flow, which can lead to more and more clots forming in the pulmonary vessels. The right heart has to pump against this suddenly increased pressure, and not enough blood reaches the left heart. This in turn leads, on the one hand, to a drop in blood pressure and insufficient blood flow to the coronary vessels, which reduces cardiac output, and, on the other hand, to too little oxygen-rich blood reaching the body and organs.
In addition, the body lacks oxygen because blood no longer reaches the area of the lungs behind the occluded vessel, leaving less surface area for oxygen exchange.
