Pulmonary Pathophysiology II: Restrictive Diseases

Pulmonary Pathophysiology II: Restrictive Lung Diseases, Other Pulmonary Diseases

• This presentation covers restrictive lung diseases and other pulmonary conditions
• Restrictive lung diseases are characterized by reduced total lung capacity, preventing complete ventilation and affecting alveolar function.
• A key characteristic is normal FEV1/FVC ratios, meaning both inspiration and expiration are impaired.
• Total lung capacity and FVC are decreased, leading to decreased capacity, but the FEV1/FVC ratio remains normal, indicating a restriction issue.
• Restrictive lung disease typically arises from parenchymal lung tissue issues, unlike obstructive diseases, which affect airways.
• Lung compliance, a measurement of lung expansion and recoil, is reduced in restrictive lung diseases.
• Reduced compliance indicates difficulty expanding the lungs during inspiration and utilizing elastic recoil for expiration. This leads to stiff lungs.
• Common causes include: interstitial lung diseases, hypersensitivity pneumonitis, exposure-induced pneumoconiosis, sarcoidosis, acute respiratory distress syndrome (ARDS), pulmonary edema, pneumonia, pneumothorax, immunologic mediated diseases, and neuromuscular disorders.
• Exposure-induced pneumoconiosis, like asbestosis, silicosis, and coal worker's pneumoconiosis, result from environmental factors like dust inhalation. Pulmonary fibrosis is the consequence of alveolar macrophage activity.

Hypersensitivity Pneumonitis

• Immune responses to minuscule environmental antigens or pathogens are responsible.
• Antigens include mold/fungi in HVAC systems, bird droppings/feathers, animal dander, and bacteria in farm environments.

Sarcoidosis

• A rare, idiopathic, systemic, multi-organ disease involving primarily macrophages and CD4 T-cells.
• Characterized by granulomas (collections of inflammatory cells) that release pro-inflammatory cytokines, leading to interstitial fibrosis.
• Prevalence is higher in African-American women.
• A characteristic clinical feature is hypervitaminosis D due to excess vitamin D produced by granulomas. This can lead to hypercalcemia and hypercalciuria.
• Corticosteroids are typically the first-line treatment.

Iatrogenic (Medication-Induced) Pneumonitis

• Medications can cause lung inflammation through various mechanisms, predominantly involving reactive oxygen species (ROS) and chemotaxis of innate immune cells.
• Common implicated drugs include nitrofurantoin, methotrexate, Bactrim, amiodarone, cyclophosphamide, and hydralazine.
• Symptoms may not emerge for months.

Acute Respiratory Distress Syndrome (ARDS)

• ARDS is an acute inflammatory lung syndrome characterized by diffuse alveolar damage, impacting gas exchange.
• Two primary types: direct, originating from pulmonary triggers, and indirect, resulting from systemic inflammation.
• Characterized by impaired gas exchange resulting from alveolar wall damage and surfactant inactivation.
• Significant pulmonary edema is a feature, and mechanical ventilation is typically required.

Pneumothorax

• Pneumothorax is a medical emergency involving air trapped in the pleural space, compressing the lungs.
• Causes include trauma, infections, or spontaneous events.
• Tension pneumothorax requires immediate needle decompression.
• Chest tubes are used in most cases for long-term treatment allowing the lung to fully re-expand

Thoracic Cage Diseases

• Diseases that affect the thoracic cage prevent expansion, limiting air entry into the alveoli making them prone to collapse.
• Neuromuscular conditions like myasthenia gravis, Guillain-Barré syndrome, muscular dystrophies, and kyphoscoliosis frequently cause thoracic cage diseases reducing lung function.

Pulmonary Embolism (PE)

• A circulatory obstruction caused by a thrombus (blood clot) usually originates from the lower extremities, lodging in a pulmonary artery.
• High risk populations include obese people, pregnant women, and those with prolonged recumbency or surgery.
• Risk factors can be smoking history, thrombophilia, and non-compliance with anticoagulant therapy.
• Large emboli can damage the heart and trigger high levels of hemodynamic instability, potentially causing obstructive shock.
• Signs and Symptoms include right-sided chest pain and shortness of breath or hemoptysis (coughing up blood).
• Imaging (CT scan) is commonly used for diagnosis.

This quiz focuses on restrictive lung diseases and other pulmonary conditions. It explores how these diseases impact lung capacity, compliance, and gas exchange while highlighting key characteristics like the normal FEV1/FVC ratio. Understand the implications of these conditions on overall pulmonary function.