Pulmonary embolism is a blockage in one of the pulmonary arteries in lungs. In most cases, pulmonary embolism is caused by blood clots that travel to the lungs from deep veins in the legs or, rarely, from veins in other parts of the body (deep vein thrombosis).

Because the clots block blood flow to the lungs, pulmonary embolism can be life-threatening. However, prompt treatment greatly reduces the risk of death. Taking measures to prevent blood clots in our legs will help protect us against pulmonary embolism.

SYMPTOMS OF PULMONARY EMBOLISM

Pulmonary embolism symptoms can vary greatly, depending on how much of lung is involved, the size of the clots, and whether have underlying lung or heart disease.

Common signs and symptoms include:

• Shortness of breath
• Chest pain
• Cough

Other signs and symptoms that can occur with pulmonary embolism include:

• Rapid or irregular heartbeat
• Lightheadedness or dizziness
• Excessive sweating
• Fever
• Leg pain or swelling, or both, usually in the calf caused by a deep vein thrombosis
• Clammy or discolored skin (cyanosis)

CAUSES OF PULMONARY EMBOLISM

Pulmonary embolism occurs when a clump of material, most often a blood clot, gets wedged into an artery in our lungs. These blood clots most commonly come from the deep veins of  legs, a condition known as deep vein thrombosis (DVT).

In many cases, multiple clots are involved in pulmonary embolism. The portions of lung served by each blocked artery are robbed of blood and may die. This is known as pulmonary infarction. This makes it more difficult for our lungs to provide oxygen to the rest of your body.

Occasionally, blockages in the blood vessels are caused by substances other than blood clots, such as:

• Fat from the marrow of a broken long bone
• Part of a tumor
• Air bubbles

RISK FACTORS

Although anyone can develop blood clots and subsequent pulmonary embolism, certain factors can increase the risk.

Someone at higher risk if there family members have had venous blood clots or pulmonary embolism in the past.

In addition, some medical conditions and treatments put at risk, such as:

• Heart disease - Cardiovascular disease, specifically heart failure, makes clot formation more likely.
• Cancer - Certain cancers  especially brain, ovary, pancreas, colon, stomach, lung and kidney cancers, and cancers that have spread can increase the risk of blood clots, and chemotherapy further increases the risk. Women with a personal or family history of breast cancer who are taking tamoxifen or raloxifene also are at higher risk of blood clots.
• Surgery - Surgery is one of the leading causes of problem blood clots. For this reason, medication to prevent clots may be given before and after major surgery, such as joint replacement.
• Disorders that affect clotting - Some inherited disorders affect blood, making it more prone to clot. Other medical disorders such as kidney disease can also increase the risk of blood clots.
• Coronavirus disease 2019 (COVID-19) - People who have severe symptoms of COVID-19 have an increased risk of pulmonary embolism.

Prolonged immobility

Blood clots are more likely to form during periods of inactivity, such as:

• Bed rest. Being confined to bed for an extended period after surgery, a heart attack, leg fracture, trauma or any serious illness makes  more vulnerable to blood clots. When the lower extremities are horizontal for long periods, the flow of venous blood slows and blood can pool in the legs, sometimes resulting in blood clots.
• Long trips. Sitting in a cramped position during lengthy plane or car trips slows blood flow in the legs, which contributes to the formation of clots.

Other risk factors

• Smoking. For reasons that aren't well understood, tobacco use predisposes some people to blood clot formation, especially when combined with other risk factors.
• Being overweight. Excess weight increases the risk of blood clots — particularly in people with other risk factors.
• Supplemental estrogen. The estrogen in birth control pills and in hormone replacement therapy can increase clotting factors in blood, especially if smoke or are overweight.
• Pregnancy. The weight of the baby pressing on veins in the pelvis can slow blood return from the legs. Clots are more likely to form when blood slows or pools.

COMPLICATION OF PULMONARY EMBOLISM

Pulmonary embolism can be life-threatening. About one-third of people with undiagnosed and untreated pulmonary embolism do not survive. When the condition is diagnosed and treated promptly, however, that number drops dramatically.

Pulmonary embolism can also lead to pulmonary hypertension, a condition in which the blood pressure in our lungs and in the right side of the heart is too high. When one have obstructions in the arteries inside the lungs,  heart must work harder to push blood through those vessels, which increases blood pressure and eventually weakens of heart.

In rare cases, small emboli occur frequently and develop over time, resulting in chronic pulmonary hypertension, also known as chronic thromboembolic pulmonary hypertension.

PREVENTION FROM PULMONARY EMBOLISM

Preventing clots in the deep veins in our legs (deep vein thrombosis) will help prevent pulmonary embolism. For this reason, most hospitals are aggressive about taking measures to prevent blood clots, including:

• Blood thinners (anticoagulants)-medications are often given to people at risk of clots before and after an operation — as well as to people admitted to the hospital with medical conditions, such as heart attack, stroke or complications of cancer.
• Compression stockings- Compression stockings steadily squeeze your legs, helping your veins and leg muscles move blood more efficiently. They offer a safe, simple and inexpensive way to keep blood from stagnating during and after general surgery.
• Leg elevation-Elevating legs when possible and during the night also can be very effective. Raise the bottom of  bed 4 to 6 inches (10 to 15 cm) with blocks or books.
• Physical activity- Moving as soon as possible after surgery can help prevent pulmonary embolism and hasten recovery overall. This is one of the main reasons nurse may push to get up, even on  day of surgery, and walk despite pain at the site of  surgical incision.
• Pneumatic compression- This treatment uses thigh-high or calf-high cuffs that automatically inflate with air and deflate every few minutes to massage and squeeze the veins in legs and improve blood flow.

Prevention while traveling

• Drink plenty of fluids.
• Take a break from sitting
• Fidget in your seat. 
• Wear support stockings.