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Pulmonary Vascular Disease: Pulmonary Embolism and Hypertension

PULMONARY VASCULAR DISEASE: PULMONARY EMBOLISM AND PULMONARY HYPERTENSION - CLINICAL MANIFESTATIONS

Chapter 21 RC122 Respiratory Care Pathophysiology

I. Pulmonary Embolism (PE)

  • Definition:
    • A blockage of the main artery of the lung or one of its branches due to an embolism.
  • Most commonly results from deep vein thrombosis (DVT) occurring in the legs and pelvis.
  • Other causes include:
    • Air embolism
    • Fat embolism
    • Amniotic fluid embolism
    • Bone marrow fragments
    • Tumor fragments
  • Consequences:
    • Leads to elevated pressure on the right ventricle of the heart.
  • Saddle embolus:
    • A type of embolism that lodges in the bifurcation of the pulmonary artery, often resulting in rapid mortality.

II. Pulmonary Embolism Anatomic Alterations

  • Blockage of the pulmonary vascular system can lead to:
    • Pulmonary infarction (especially in the case of severe embolism).
    • Alveolar atelectasis.
    • Alveolar consolidation.
    • Bronchospasm.

III. Virchow’s Triad

  • Three primary factors associated with the formation of DVT:
    1. Venous stasis:
    • Definition: Slowing or stagnation of blood flow through the veins.
    1. Hypercoagulability:
    • Definition: An increased tendency of blood to form clots.
    1. Endothelial injury:
    • Injury to the endothelial cells that line the blood vessels.

IV. Pulmonary Embolism Risk Factors

  • Venous Stasis:
    • Inactivity
    • Prolonged bed rest or sitting
    • Congestive heart failure
    • Varicose veins
    • Thrombophlebitis:
      • Definition: Inflammation of a vein due to any insult to the blood vessel wall.
    • Surgical procedures involving hip, pelvis, or knee.
    • Trauma, particularly bone fractures of the pelvis and long bones.
  • Hypercoagulative Disorders:
    • Thrombophilia
  • Other risk factors include:
    • Obesity
    • Pacemakers
    • Pregnancy and childbirth
    • Smoking
    • Burns
    • Supplemental estrogen
    • Malignant neoplasms
    • Family history of clotting disorders.

V. Pulmonary Infarction

  • Process:
    • An embolus significantly disrupts blood flow, causing lung tissue death (infarction).
  • Most common among patients with chronic cardiac or pulmonary diseases.
  • Small emboli typically do not cause major issues; however, large emboli can result in sudden death.

VI. Clinical Manifestations of Pulmonary Embolism

  • Symptoms include:
    • Increased heart rate (HR)
    • Increased respiratory rate (RR):
      • Stimulation of peripheral chemoreceptors due to hypoxemia leads to increased RR.
    • Development of pulmonary hypertension due to a decreased cross-sectional area of the pulmonary vascular system, causing reduced cardiac return and systemic hypotension.
    • Sudden onset of dyspnea (shortness of breath).
    • Severe chest pain, resembling angina, accompanied by decreased chest expansion.
    • Anxiety and diaphoresis (excessive sweating).
    • Cyanosis (bluish discoloration due to low oxygen levels).
    • Coughing, potentially with hemoptysis (coughing up blood).
    • Auscultation may reveal crackles, wheezes, and pleural friction rub.
    • Abnormal heart sounds, including right ventricular heave or lift.
    • Syncope (fainting), light-headedness, or confusion.
    • Peripheral edema and venous distention.

VII. Right Ventricular Lift

  • Resulting from elevated pulmonary blood pressure, leading to right ventricular strain or hypertrophy.
  • A sustained lift can be palpated along the left sternal border during systole.

VIII. Electrocardiogram (EKG) Changes

  • No definitive EKG pattern exists for diagnosing pulmonary embolism.
  • The most common abnormal finding is sinus tachycardia:
    • Defined as a heart rate exceeding 100 beats per minute.

IX. Diagnosis and Screening for Pulmonary Embolism

  • Diagnosis is predominantly based on clinical manifestations followed by various testing methods:
    • Blood Tests:
    • D-dimer blood test (fibrinogen test).
    • Ultrasonography:
    • Effective in detecting DVT.
    • Chest X-Ray:
    • Rules out conditions that mimic PE.
    • Computed Tomography Pulmonary Angiogram (CTPA):
    • Currently the primary test for diagnosing suspected PE.
    • Ventilation-Perfusion (V/Q) Scan:
    • Largely replaced by CTPA.
    • Pulmonary Angiogram
    • Magnetic Resonance Imaging (MRI):
    • Magnetic Resonance Angiography (MRA):

A. Blood Tests

  • Tests conducted include:
    • Complete blood count (CBC)
    • Clotting status evaluation
    • Electrolytes test
    • Blood urea nitrogen (BUN) for renal function
    • Liver enzymes assessment
  • If genetic abnormalities regarding clotting systems are detected, lifelong anticoagulant therapy may be recommended.

B. D-dimer Blood Test

  • Purpose: To detect increased levels of plasma protein fibrinogen.
  • A level > 500 ng/mL is considered positive, potentially indicating the presence of blood clots.
  • Many conditions can raise D-dimer levels, so a normal result effectively rules out blood clots.

C. Ultrasonography

  • Function: Utilizes high-frequency sound waves to identify blood clots, particularly in thigh veins.
  • Noted for its accuracy in diagnosing clots in knee or thigh regions but is less sensitive for clots below the knee.

X. Chest X-Ray Results

  • May reveal:
    • Peripheral wedge-shaped infiltrates
    • Increased density in infarcted areas
    • Hyperradiolucency distal to the embolus
    • Dilation of pulmonary arteries
    • Pulmonary edema
    • Right ventricular cardiomegaly (cor pulmonale)
    • Small pleural effusions.
  • Note: Chest X-rays can appear normal for PE, but they are beneficial for ruling out similar conditions like pneumonia.

XI. Computed Tomography Pulmonary Angiogram

  • Involves CT imaging with intravenous contrast.
  • This has become the first-line test for suspected pulmonary embolism, specifically for detecting thrombus in the right pulmonary artery.

XII. Ventilation-Perfusion (V/Q) Scan

  • Rarely used today for PE identification, replaced by CTPA.
  • Methodology: Involves the use of radioactive material inhaled and injected into the bloodstream to assess airflow and blood flow in the lungs.

XIII. Deadspace Ventilation in Pulmonary Embolism

  • Definition: Ventilated alveoli that experience no perfusion due to blockage.
  • Importance: Underlines the concept that ventilation can exceed perfusion in cases of pulmonary embolism.

XIV. Pulmonary Angiography

  • Method: A catheter is inserted into a vein (usually in the groin or neck) and guided into the pulmonary artery.
  • A dye is injected to highlight any obstructions in blood flow.
  • Note: This is invasive and time-consuming and is rarely performed today.

XV. Arterial Blood Gases (ABG)

  • Findings:
    • Mild to moderate cases show acute alveolar hyperventilation with hypoxemia.
    • Severe cases illustrate acute ventilatory failure alongside hypoxemia.

XVI. Pharmacologic Agents

  • Anti-coagulants:
    • Prevent the expansion of existing blood clots and the formation of new ones.
    • Common examples: Heparin and Warfarin.
    • Safer and effective alternatives include enoxaparin, dalteparin, and tinzaparin (all low molecular weight heparins).
  • Thrombolytics (fibrinolytics):
    • Designed to dissolve blood clots (clot-busters).
    • Examples: Streptokinase, urokinase, alteplase, and reteplase.

A. Low Molecular Weight Heparins (LMWHs)

  • Enoxaparin (Lovenox):
    • Usage: Commonly used for prevention and treatment of DVT and PE.
    • Advantages: Longer half-life, better bioavailability, and more predictable anticoagulant response versus unfractionated heparin (UFH).
  • Dalteparin (Fragmin):
    • Usage: Similar indications as enoxaparin relevant to DVT, PE, and clot prevention in cancer patients.
    • Advantages: Noted safety profile in patients with renal impairment.
  • Tinzaparin (Innohep):
    • Usage: Pertinent for DVT and PE treatment and used in patients undergoing dialysis.
    • Advantages: Effective in severe renal impairment with a lower bleeding risk.

XVII. Pulmonary Embolism Treatment

  • Preventive measures:
    • Walking, seated exercises, and hydration.
    • Graduated compression stockings to aid in preventing venous stasis.
    • Pneumatic compression devices for the leg.
    • Inferior vena cava filters used in specific cases, though effectiveness and safety are not well established.
    • Pulmonary embolectomy: A surgical option for clot removal with associated high mortality rates.

XVIII. Respiratory Care Treatment Protocols

  • Oxygen Therapy Protocol:
    • Deliver 100% oxygen (FiO2 of 1.0).
  • Aerosolized Medication Protocol:
    • Bronchodilators administered in cases of wheezing.

XIX. Pulmonary Hypertension

  • Definition:
    • Pulmonary hypertension (PH) is characterized by an increase in mean pulmonary artery pressure greater than 25 mm Hg; normal ranges are between 10 to 20 mm Hg at rest.
  • Common as a complication of chronic pulmonary disease (e.g., COPD and interstitial lung disease) with a prevalence ratio of 3:1 for women compared to men.
  • PH can result from left or right-sided heart failures, with left-sided heart failure being the more common cause.

XX. Understanding Pulmonary Hypertension

  • Description:
    • Abnormally high blood pressure within the pulmonary arteries necessitating the heart to work harder to pump blood.
  • Consequences:
    • Increased pressure results in damaged pulmonary arteries with thickening of vessel walls.
    • Resulting dysfunction in gas exchange (oxygen and carbon dioxide).
    • Decreased oxygen levels may lead to polycythemia (increased red blood cells) and further pulmonary arterial constriction increasing pressure.

XXI. Primary Pulmonary Hypertension

  • Also known as Idiopathic Pulmonary Hypertension:
    • An unknown cause.

XXII. Secondary Pulmonary Hypertension

  • Results from other medical conditions including:
    • Diseases that impede blood flow through the lungs or cause hypoxemia.
    • Risk factors include:
    • Recurring blood clots in the lungs.
    • Left-sided congestive heart failure.
    • Chronic lung diseases.
    • Illicit drug use.
    • Certain medications and rheumatologic conditions.
    • Inflammation of the pulmonary blood vessels.
    • Example conditions:
    • COPD, obstructive sleep apnea, cystic fibrosis, and various chronic lung diseases.

XXIII. Pulmonary Hypertension Classification

  • Classified by the WHO into five groups based on the underlying cause, guiding diagnostics and treatment:
    • Group 1: Pulmonary Arterial Hypertension (PAH)
    • Includes idiopathic, heritable, drug-induced PAH, and PAH linked to systemic diseases.
    • Group 2: PH due to left heart disease (most common).
    • Related to left ventricular dysfunction and valvular heart disease.
    • Group 3: PH due to lung diseases and/or hypoxia (e.g., COPD, sleep apnea).
    • Group 4: Chronic thromboembolic pulmonary hypertension (CTEPH).
    • Group 5: PH with unclear or multifactorial mechanisms.

XXIV. Clinical Manifestations of Pulmonary Hypertension

  • Symptoms include:
    • Shortness of breath or dizziness are often the first indications.
    • Racing heartbeat, arrhythmias, peripheral edema, and distended neck veins.
    • Cyanosis (bluish skin due to insufficient oxygen).
    • Generalized fatigue and dizziness, possibly leading to fainting (syncope).
    • Chest pain or pressure, including coughing or hemoptysis.
    • Note: Many patients may remain asymptomatic for extended periods.

XXV. Diagnostic Tests for Pulmonary Hypertension

  • Echocardiography:
    • Assesses size and thickness of the right ventricle and estimates pulmonary artery pressure.
  • Chest X-Ray:
    • Can identify enlargement of pulmonary arteries and the right ventricle.
  • Electrocardiogram (ECG):
    • Evaluates rhythm regularity.
  • CT Scan:
    • Used to exclude underlying causes of pulmonary hypertension.
  • Right Heart Catheterization:
    • Confirms PH diagnosis and assesses damage severity.
  • Six Minute Walk Test (6MWT):
    • Evaluates functional capacity; walking less than 300 meters indicates poor prognosis, while ≥500 meters suggests a better outlook.
  • Chest MRI:
    • Shows right ventricle function and blood flow.
  • Pulmonary Function Tests (PFTs):
    • Ruling out restrictive or obstructive lung diseases.
  • Polysomnogram:
    • Evaluates apneas and oxygen levels during sleep.
  • VQ Scan:
    • Detect blood clots in the lungs.
  • Blood Tests:
    • Ruling out other diseases such as HIV and liver issues; cardiac catheterization can check vasoreactivity, indicating potential benefits from triggering medication.

XXVI. Chest X-Ray in Pulmonary Hypertension

  • Findings may include:
    • Peripheral pruning (hypovascularity) of pulmonary vessels.
    • Prominent hilar pulmonary arteries indicating right ventricular enlargement.

XXVII. Right Heart Catheterization

  • Process: Involves inserting a thin catheter into the right side of the heart and pulmonary arteries.
  • Purpose: Monitors heart function and blood flow, allowing for pressure assessment within the heart and pulmonary system.

XXVIII. Treatment of Pulmonary Hypertension

  • Treatment involves managing the underlying cause, as no definitive cure exists.
  • Prognosis for idiopathic pulmonary arterial hypertension (IPAH) is poor without therapy, with only 33% survival at five years.
  • Medication options include:
    • Diuretics to reduce fluid retention.
    • Blood thinners to prevent clot formation.
    • Digoxin to enhance heart strength.
    • Inhaled pulmonary vasodilators such as Iloprost and Trepostinil.
    • Inhaled nitric oxide for persistent pulmonary hypertension of the newborn (PPHN).
    • Oxygen therapy for hypoxemia.
    • Encouraging physical activity to improve exercise tolerance.