5.6: Pulmonary Disorders — Pulmonary Embolism, ARDS, Respiratory Acidosis

What is a pulmonary embolism (PE)?

A blockage in a branch of the pulmonary artery by a substance

What types of substances can cause a pulmonary embolism?

Thrombus, air, fat, or amniotic fluid

What is the most common cause of pulmonary embolism?

Thrombi from deep vein thrombosis (DVT)

Where do most emboli originate from?

Lower and upper extremities

How many deaths per year are caused by pulmonary embolism in the US?

Approximately 50,000

What does a pulmonary embolism obstruct?

Blood flow in the pulmonary artery

What effect does PE have on gas exchange?

It impairs gas exchange

What happens to blood vessels in the lungs during PE?

Vasoconstriction occurs

What can PE lead to in the lungs?

Pulmonary hypertension

What heart complication can result from PE?

Right heart failure

What is Virchow triad?

Three factors that predispose to venous thrombosis

What are the three components of Virchow triad?

Venous stasis, endothelial injury, and hypercoagulability

What are examples of inherited hypercoagulability disorders?

Antithrombin III deficiency, protein C and S deficiencies, factor V Leiden mutation

What causes venous stasis?

Prolonged bed rest or immobility

What causes venous endothelial injury?

Trauma, surgery, or fractures

What conditions increase risk of thrombosis?

Childbirth, MI, CHF, cancer, and spinal cord injury

What do symptoms of pulmonary embolism depend on?

The size and location of the obstruction

What are the most common symptoms of pulmonary embolism?

Chest pain, dyspnea, cough, and increased respiratory rate

What is pleuritic pain?

Pain that worsens with inspiration

What gas exchange issue occurs in PE?

Moderate hypoxemia

When can small emboli be asymptomatic?

In peripheral branches unless the person is elderly or acutely ill

What is the outcome of massive pulmonary emboli?

They are often fatal

How is pulmonary embolism diagnosed?

History, physical exam, ABGs, D-dimer, imaging, and other tests

What is the purpose of lab and radiologic studies in PE?

To rule out other causes of chest pain or dyspnea

What test helps locate the source of a PE?

Lower extremity ultrasonography

What does the D-dimer test measure?

Plasma D-dimer from clot breakdown

What does an elevated D-dimer indicate?

A thromboembolic event

Why might troponin levels be elevated in PE?

Right ventricle stretching from pulmonary infarction

What does a ventilation-perfusion (V/Q) scan evaluate?

Blood flow and gas distribution in lung segments

What imaging test detects emboli in pulmonary arteries?

Helical (spiral) CT scan

What is the main treatment for pulmonary embolism?

Anticoagulant therapy

What medication is an example of anticoagulant therapy?

Lovenox

When is thrombolytic therapy used in PE?

For large or multiple emboli

What is the goal of PE treatment?

Restore pulmonary blood flow

How can anticoagulants be used preventively?

To prevent DVT or PE after surgery

What are prevention strategies for PE?

Increasing mobility and using compression devices

What devices help prevent venous stasis?

Compression stockings and pneumatic compression boots

What is ARDS?

A condition caused by various factors leading to severe lung injury

What types of events can cause ARDS?

Aspiration, infection, trauma, toxins, and shock

What are examples of aspiration causes of ARDS?

Near drowning and aspirating gastric contents

What drugs can contribute to ARDS?

Free-base cocaine and heroin

What inhaled substances can cause ARDS?

Smoke and ammonia

What oxygen-related factor can cause ARDS?

Breathing high concentrations of oxygen

What medical treatment can lead to ARDS?

Radiation

What type of infection can lead to ARDS?

Septicemia

What trauma-related causes can lead to ARDS?

Burns, fat embolism, and chest trauma

What coagulation-related condition can cause ARDS?

Disseminated intravascular coagulation

What blood-related cause can lead to ARDS?

Multiple blood transfusions

What is the common lung change in ARDS?

Diffuse epithelial cell injury

What happens to the alveolar-capillary membrane in ARDS?

Increased permeability

What substances leak into the alveoli in ARDS?

Fluid, protein, debris, platelets, and blood cells

What immune cells contribute to lung damage in ARDS?

Activated neutrophils

What do neutrophils release in ARDS?

Products that damage alveolar cells

What complications occur due to alveolar damage in ARDS?

Edema and surfactant inactivation

What is a hyaline membrane?

A layer formed in the alveoli that resists gas exchange

What effect does hyaline membrane formation have?

It impairs gas exchange

What type of lung injury occurs in ARDS?

Diffuse epithelial cell injury

What happens to the alveolar-capillary membrane in ARDS?

Its permeability increases

What leaks into the interstitium and alveoli in ARDS?

Fluid, protein, cellular debris, platelets, and blood cells

Which immune cells contribute to lung damage in ARDS?

Activated neutrophils

What do activated neutrophils release in ARDS?

Products that damage alveolar cells

What complications result from alveolar cell damage in ARDS?

Edema, surfactant inactivation, and hyaline membrane formation

What is the effect of hyaline membrane formation?

It resists gas exchange

How does ARDS affect lung stiffness?

The lung becomes stiff

How does lung stiffness affect breathing?

It becomes more difficult

What type of blood flow abnormality occurs in ARDS?

Shunting

What happens to gas exchange in ARDS?

It is impaired

What oxygenation problem occurs in ARDS?

Hypoxemia despite high supplemental oxygen

Why do alveoli collapse in ARDS?

Surfactant is inactivated

What long-term structural change can occur in severe ARDS?

Fibrosis

When does ARDS typically present after a triggering event?

Within 12-18 hours

What are the main clinical features of ARDS?

Rapid respiratory distress, increased respiratory rate, and respiratory failure

What oxygen abnormality occurs in ARDS?

Hypoxemia

What severe systemic complication can occur in ARDS?

Multiple organ failure

What does a chest x-ray show in ARDS?

Diffuse bilateral infiltrates (white-out)

How is cardiac function in ARDS?

Normal

What is the main focus of ARDS treatment?

Supportive care with oxygen and ventilator support

What must be addressed in ARDS treatment?

The underlying cause

What complication may occur during ARDS recovery?

Lung scarring and fibrosis

What is respiratory acidosis?

A condition caused by impaired alveolar ventilation leading to increased CO2 and decreased pH

What happens to PCO2 in respiratory acidosis?

It increases (hypercapnia)

What happens to pH in respiratory acidosis?

It decreases

What is the most common cause of respiratory acidosis?

Decreased ventilation

Can respiratory acidosis be acute or chronic?

Yes, both

What are causes of respiratory center depression?

Drug overdose and head injury

What lung diseases can cause respiratory acidosis?

Asthma, COPD, pneumonia, pulmonary edema, and respiratory distress syndrome

What types of conditions affect chest wall and muscles causing respiratory acidosis?

Paralysis, chest injuries, kyphoscoliosis, extreme obesity, and paralytic drugs

What environmental factor can cause respiratory acidosis?

Breathing air with high CO2 content

What happens to HCO3- in respiratory acidosis?

It increases as compensation

What happens to cerebral vessels in respiratory acidosis?

They dilate

What neurological symptoms occur in respiratory acidosis?

Headache, weakness, confusion, depression, paranoia, hallucinations

What severe neurological outcomes can occur in respiratory acidosis?

Stupor and coma

What happens to the skin in respiratory acidosis?

It becomes warm and flushed

What is a sign of compensation in respiratory acidosis?

Acid urine

What acute conditions can cause respiratory acidosis?

Narcotic overdose, lung disease, chest injury, muscle weakness, and airway obstruction

What chronic condition commonly causes respiratory acidosis?

COPD

Why must oxygen be carefully controlled in COPD patients?

Their respiratory drive depends on low PO2 rather than high CO2

What happens if too much oxygen is given to COPD patients?

It suppresses the respiratory drive

Why does respiratory drive shift in COPD patients?

The medullary center adapts to chronically high CO2 levels

What can cause increased carbon dioxide production?

Exercise, fever, sepsis, and burns