Pulmonary embolism is a life-threatening medical emergency that occurs when a blood clot (embolus) blocks a pulmonary artery in the lungs. This obstruction disrupts blood flow to the alveoli, where gas exchange should occur, leading to impaired oxygenation and potentially fatal hypoxemia.
Pathophysiology
A PE usually originates from a deep vein thrombosis (DVT) — a clot in the deep veins, most often in the legs. If part of this clot breaks loose, it travels through the bloodstream to the pulmonary arteries, blocking blood flow and reducing oxygen delivery to the body.
The result:
- Impaired gas exchange
- Increased pulmonary artery pressure
- Strain on the right side of the heart
- Potential cardiovascular collapse if untreated
Causes
- Deep Vein Thrombosis (DVT) — the primary source
- Fat embolism after bone fracture
- Air embolism from IV lines or trauma
- Amniotic fluid embolism during childbirth
Risk Factors
Certain factors increase the risk of clot formation and PE:
- Smoking – damages blood vessels and increases clotting tendency
- Obesity – slows circulation and promotes clot formation
- Immobility – prolonged bed rest, long flights, or post-surgical recovery
- Cardiac conditions – atrial fibrillation, valve disorders
- Hormonal influences – estrogen therapy or oral contraceptives (major NCLEX-tested point)
Memory Trick: E = Estrogen, E = Emboli
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Signs and Symptoms
Most Important Sign: Hypoxemia (low blood oxygen)
- Restlessness
- Agitation
- Mental status changes
Other Symptoms:
- Sudden chest pain
- Dyspnea (shortness of breath)
- Tachypnea (rapid breathing)
- Tachycardia (fast heart rate)
- Anxiety
Diagnosis
D-Dimer Test – Detects fibrin degradation products in the blood; a positive result suggests clot formation.Memory Trick: D = Dimer → Dime-sized clot in body
CT Pulmonary Angiography – Gold standard for visualizing PE
V/Q Scan – Measures ventilation-perfusion mismatch
Ultrasound of Legs – Detects DVT as source of emboli
Pharmacology
Anticoagulants – Prevent clot extension
- Heparin – Rapid-acting, given IV or subcutaneously
- Warfarin – Oral, for long-term prevention
Thrombolytics – Dissolve existing clots (for severe PE)
- tPA (Tissue Plasminogen Activator)
- Alteplase
- Streptokinase
Note: Thrombolytics carry a high bleeding risk — used only in life-threatening PE or hemodynamic instability.
Surgical and Interventional Treatments
- Embolectomy – Surgical removal of clot in severe cases
- Vena Cava Filter – Placed in inferior vena cava to prevent new clots from reaching lungs
Prevention
- Early mobilization after surgery
- Compression stockings for high-risk patients
- Anticoagulant prophylaxis in hospitalized patients
- Lifestyle changes: quit smoking, maintain healthy weight
Quick Reference Table: Pulmonary Embolism Overview
| Feature | Description |
|---|---|
| Definition | Blood clot blocking a pulmonary artery |
| Main Cause | Deep vein thrombosis (DVT) |
| Key Risk Factors | Smoking, obesity, immobility, estrogen use |
| #1 Sign | Hypoxemia |
| Other Symptoms | Chest pain, dyspnea, tachycardia, anxiety |
| Diagnostics | D-dimer, CT angiography, V/Q scan |
| Treatment | Anticoagulants, thrombolytics, surgery |
Frequently Asked Questions (FAQs)
1. How fast can a PE become fatal?
A massive PE can cause sudden death within minutes if untreated, making rapid diagnosis critical.
2. Can you have a PE without symptoms?
Yes, small emboli may cause mild or no symptoms, but they can still be dangerous if multiple occur.
3. How long do you need anticoagulation after PE?
Usually 3–6 months for a first episode, longer for recurrent or unprovoked PE.
4. Is PE preventable?
Yes, through early mobility, anticoagulation in high-risk patients, and lifestyle modifications.
5. Can PE recur?
Yes — without preventive measures, recurrence risk is high.
