cc 2.1

What is a pulmonary embolism (PE)?

A critical medical condition caused by a blockage in one or more pulmonary arteries.

What is the most common cause of a pulmonary embolism?

A thrombus (blood clot) that has traveled from another part of the body.

Where do most clots causing PE originate?

The legs, most commonly from a deep vein thrombosis (DVT).

What happens when a clot obstructs a pulmonary artery?

Blood flow to the lung tissue supplied by that artery is obstructed.

Why can't the affected lung tissue adequately oxygenate blood during a PE?

Blood cannot reach the affected alveoli to pick up oxygen.

What can happen to lung tissue if a PE is sufficiently large?

The affected lung tissue can infarct and die.

What is a thrombus?

A blood clot that forms within a blood vessel.

What is an embolus?

Material that travels through the bloodstream and becomes lodged in a blood vessel.

What is the most common type of embolus causing PE?

A blood clot.

What are non-thrombotic emboli?

Emboli made of materials other than blood clots.

What can cause a fat embolus?

Fractures of large bones, such as the femur or pelvis.

What can cause an air embolus?

Improper removal of central venous lines or accidental injection of air through an IV.

What is a tumor embolus?

A fragment of a cancerous tumor that travels through the bloodstream.

What is an amniotic fluid embolism?

A rare complication of childbirth in which amniotic fluid enters the maternal circulation.

What happens first in the pathophysiology of a PE?

A clot lodges in a pulmonary arterial vessel.

What happens to pulmonary vascular resistance when a clot lodges in a pulmonary artery?

Pulmonary vascular resistance immediately increases.

How does increased pulmonary vascular resistance affect the right ventricle?

The right ventricle must pump against much higher pressure.

What happens to the right ventricle when it must pump against massive pressure?

It dilates, works harder, and can eventually fail.

What can result from right ventricular failure during a massive PE?

Shock.

What happens when the clot interacts with vessel linings and platelets?

It triggers the release of chemical mediators.

Which chemical mediators are released during PE-related vascular reactions?

Serotonin and thromboxane A2.

What effect do serotonin and thromboxane A2 have on blood vessels?

They cause widespread vasoconstriction.

What respiratory imbalance does a PE create?

Alveolar dead space.

What is alveolar dead space?

Ventilation without adequate perfusion.

Why does a PE create alveolar dead space?

Air can enter the alveoli, but blood cannot flow past them because the pulmonary artery is blocked.

What happens to oxygen levels because of the V/Q mismatch in PE?

Hypoxemia develops.

How can PE cause atelectasis?

Loss of blood flow can stop surfactant production, contributing to alveolar collapse.

Is PE primarily a ventilation problem or a perfusion problem?

A perfusion problem.

Why is PE considered a perfusion problem?

Air can still enter the alveoli, but blood cannot adequately flow past them for gas exchange.

What happens to ventilation during PE?

Air can still enter the affected alveoli.

What happens to perfusion during PE?

Blood flow to affected alveoli is reduced or blocked.

What type of V/Q mismatch occurs with PE?

Ventilation exceeds perfusion.

What is the result when ventilation exceeds perfusion?

Alveolar dead space.

What happens to the pulmonary vessel lining during PE?

The clot damages the endothelium and triggers inflammation.

What is the endothelium?

The inner lining of a blood vessel.

What happens to the airways during the inflammatory response to PE?

Bronchoconstriction can occur.

What causes bronchoconstriction during PE?

Inflammatory mediators released in response to endothelial injury.

How does bronchoconstriction affect the alveoli?

It further limits airflow into the alveoli.

What is hypoxemia?

Low oxygen levels in the blood.

Why does hypoxemia occur with PE?

Blocked pulmonary blood flow and bronchoconstriction interfere with effective gas exchange.

What part of the heart is most affected by a large PE?

The right side of the heart, especially the right ventricle.

What does the right ventricle normally do?

It pumps deoxygenated blood into the pulmonary arteries.

How does a large PE affect right-ventricular workload?

It dramatically increases the pressure against which the right ventricle must pump.

Why is the right ventricle vulnerable during a large PE?

It is highly sensitive to sudden pressure changes.

What happens to blood when the right ventricle struggles against the increased pulmonary resistance?

Blood backs up, causing right-ventricular volume overload.

What happens to the right ventricle during severe volume overload?

It dilates and can rapidly begin to fail.

What happens to blood flow to the left side of the heart when the right ventricle fails?

Less blood reaches the left ventricle.

What happens to cardiac output when less blood reaches the left ventricle?

Cardiac output decreases.

What type of shock can result from severe PE?

Obstructive shock.

What is obstructive shock?

A life-threatening condition in which an obstruction prevents adequate blood flow to the body's tissues.

Why can PE cause obstructive shock?

Right-ventricular failure decreases forward blood flow to the left side of the heart and the systemic circulation.

Why is PE with cardiac dysfunction a medical emergency?

Immediate intervention may be necessary to prevent death.

What is Virchow's triad?

Three major factors that contribute to DVT formation: venous stasis, hypercoagulability, and vascular endothelial damage.

Why is Virchow's triad important when assessing PE?

DVT is the most common source of a PE.

What are the three components of Virchow's triad?

Venous stasis, hypercoagulability, and vascular endothelial damage.

What is venous stasis?

Slow or pooled blood flow within the veins.

How can prolonged immobility cause venous stasis?

Remaining still for long periods slows venous blood flow.

What situations can cause prolonged immobility?

Bed rest, long-distance travel, and casting.

Why are long-distance travelers at risk for DVT?

Prolonged sitting can cause venous stasis.

Why are long-haul truck drivers at risk for DVT and PE?

Long periods of sitting contribute to venous stasis.

How can heart failure contribute to venous stasis?

An inefficient cardiac pump can cause blood to pool.

How can varicose veins contribute to venous stasis?

Damaged venous valves allow blood to pool.

What is hypercoagulability?

An increased tendency of the blood to clot.

What types of events can cause hypercoagulability?

Trauma and major surgery.

How can cancer increase DVT risk?

Cancer can create a hypercoagulable state.

How does pregnancy increase DVT risk?

Pregnancy is associated with increased blood-clotting tendency.

How can estrogen-containing contraceptives affect DVT risk?

They can contribute to hypercoagulability.

How can hormone replacement therapy affect DVT risk?

It can contribute to hypercoagulability.

What genetic disorder listed in the notes increases clotting risk?

Factor V Leiden mutation.

What is vascular endothelial damage?

Injury to the inner lining of a vein.

What can cause vascular endothelial damage?

Trauma and surgery.

How can atherosclerosis contribute to endothelial damage?

It can damage the inner lining of blood vessels.

What indwelling devices can contribute to endothelial damage?

Central venous catheters and cardiac catheterization sheaths.

Where does a DVT typically form?

In large veins of the leg.

What is a proximal DVT?

A DVT located in an upper-leg vein.

Which veins are examples of proximal DVT locations?

External iliac, deep femoral, great saphenous, and popliteal veins.

Why are proximal DVTs more dangerous?

They are more unstable and more likely to dislodge and travel to the lungs.

Why can proximal DVTs form larger emboli?

Larger veins can hold larger clots.

What is a distal DVT?

A DVT located in the lower-leg veins.

Which veins are examples of distal DVT locations?

Anterior and posterior tibial veins.

How do distal DVTs compare with proximal DVTs?

They are generally more stable and less likely to dislodge.

Can a distal DVT become more dangerous?

Yes. The clot can propagate upward and become proximal.

What is clot propagation?

Growth or extension of a clot into larger or more proximal veins.

What is the most classic subjective respiratory symptom of PE?

Sudden-onset dyspnea.

How might a patient describe dyspnea from PE?

“I feel like I can't catch my breath.”

What is pleuritic chest pain?

Sharp chest pain that worsens with breathing.

How might a patient describe pleuritic chest pain?

“It's a sharp pain in my chest when I breathe in.”

What psychological sensation can occur with PE?

A sense of impending doom.

How might a patient describe a sense of impending doom?

“I feel like something terrible is about to happen” or “I feel like I might die.”

What emotional symptoms can occur with PE?

Anxiety and restlessness.

What respiratory-rate change commonly occurs with PE?

Tachypnea.

What is tachypnea?

Rapid breathing.

What heart-rate change commonly occurs with PE?

Tachycardia.

What temperature finding can occur with PE?

Low-grade fever.

What blood-pressure change can occur with severe PE?

Hypotension.

What cough finding can occur with PE?

Cough, sometimes with hemoptysis.

What is hemoptysis?

Coughing up blood.

What is a pleural friction rub?

A harsh, grating sound heard during respiratory assessment.

What heart sounds may occur with PE?

Extra heart sounds such as S3 or S4.

Where may S3 or S4 be particularly notable in PE?

On the right side of the chest.