Understanding Restrictive Lung Diseases

Oct 1, 2024

Restrictive Lung Diseases

Restrictive lung diseases are characterized by a reduction in lung volume, making it difficult for air to enter the lungs. They are categorized into two types:

Types of Restrictive Lung Diseases

  1. Interstitial
    • Damage to lung tissue itself.
    • Lungs become hard and stiff, reducing lung volume.
  2. Extrapulmonary
    • Damage to structures around the lung, preventing chest expansion.

Mechanics of Breathing

  • Inhalation
    • Diaphragm and intercostal muscles contract, expanding chest cavity.
    • Creates vacuum pulling lungs open, allowing air to reach alveoli where gas exchange occurs.
  • Exhalation
    • Muscles relax, chest cavity returns to normal size.
    • Elastin and collagen fibers allow lungs to spring back and push air out.

Lung Volume Measurements

  • Total Lung Capacity (TLC): Total air lungs can hold.
  • Tidal Volume: Air inhaled during normal inhalation.
  • Functional Residual Capacity: Air left after normal exhalation.
  • Forced Vital Capacity (FVC): Max air exhaled after full inhalation.
  • Forced Expiratory Volume in One Second (FEV1): Air exhaled in one second after maximum inhalation.
  • Normal FEV1/FVC ratio is 0.8.

Interstitial Restrictive Lung Diseases

  1. Pneumoconiosis

    • Occupational exposure related diseases.
    • Types include:
      • Coal Workers’ Pneumoconiosis: Inhalation of coal dust.
      • Silicosis: Inhalation of silica, causing fibrotic nodules and increased TB risk.
      • Asbestosis: Asbestos exposure, leading to pleural plaques.
    • Particles cause immune reactions, cytokine release, and fibroblast activity.

  2. Sarcoidosis

    • Systemic disease with unknown mechanism.
    • Granulomas form in lymph nodes, particularly in lung hilum.
    • Can lead to fibrosis due to pro-inflammatory cytokines.

  3. Hypersensitivity Pneumonitis

    • Immune reaction to particles like bird droppings, mold.
    • Chronic exposure leads to fibrosis.
  • Fibrosis: Replacement of healthy lung tissue with collagen fibers, causing lungs to be stiff and reducing lung capacity.
  • Impact on Lung Function: Decreased TLC, FVC, FEV1; FEV1/FVC ratio may remain same or increase.
  • Complications: Hypoxia, pulmonary hypertension, right ventricular hypertrophy (cor pulmonale).

Extrapulmonary Restrictive Lung Diseases

  • Caused by:
    • Chest wall or diaphragm abnormalities.
    • Obesity or fluid buildup (pleural effusion).
    • Neuromuscular diseases (e.g., myasthenia gravis).

Diagnosis and Treatment

  • Diagnosis:
    • Spirometry shows decreased TLC, FVC, FEV1 but normal/increased FEV1/FVC.
    • Imaging shows diffuse ground-glass opacities.
  • Treatment:
    • Interstitial: Corticosteroids, immunosuppressive drugs, anti-fibrotic therapies.
    • Extrapulmonary: Manage underlying condition.

Summary

  • Interstitial diseases involve lung tissue becoming fibrotic, reducing lung capacities.
  • Extrapulmonary diseases involve issues with structures aiding lung expansion.
  • Diagnosis via spirometry and imaging, treatment with medication and managing underlying conditions.