Restrictive Lung Disease

14/06/2013 by admin | Respiratory

Restrictive Lung Disease

Definition

are a category of extrapulmonary, pleural, or parenchymal respiratory diseases that restrict lung expansion resulting in a decreased lung volume (reduced TLV), reduced RV, an increased work of breathing, and inadequate ventilation and/or oxygenation.

Diagnostic tools/investigations

  1. o FEV1 reduced
  2. o FVC reduced (TLC <80% and reduced RV)
  3. o Therefore – FEV1/FVC = normal (or even slightly raised)

 

Aetiology

Restrictive lung diseases may be due to specific causes which can be intrinsic to the parenchyma of the lung, or extrinsic to it

Intrinsic

  1. Asbestosispleural plaquesmesothelioma
  2. Radiation therapy fibrosis / radiation pneumonitis (within RT area, after 3/12 exposure in 10-15%)
  3. Certain drugs such as amiodarone, bleomycin and methotrexate.
  4. Rheumatoid Arthritis (RA nodules and pneumoconiosis [coal workers] = Caplan’s syndrome).
  5. Infant respiratory distress syndrome due to a deficiency of surfactant in the lungs
  6. Hypersensitivity pneumonitis (Extrinsic Allergic Alveolitis) due to an allergic reaction to inhaled particles.
  7. Acute respiratory distress syndrome (ARDS) – caused by…
    1. o Mechanical ventilation
    2. o Sepsis
    3. o Pneumonia
    4. o Shock
    5. o Aspiration
    6. o Trauma (especially pulmonary contusion)
    7. o Major surgery
    8. o Massive transfusions
    9. o Smoke inhalation
    10. o Drug reaction or overdose
    11. o Fat emboli and reperfusion pulmonary oedema after lung transplantation
    12. o Pulmonary embolectomy

 

Many cases of restrictive lung disease are idiopathic (have no known cause). Still, there is generally pulmonary fibrosis. Examples are:

  1. Idiopathic pulmonary fibrosis (IPF) / cryptogenic fibrosing alveolitis (CFA) = MOST COMMON RLD
  2. Idiopathic interstitial pneumonia, of which there are several types
  3. Sarcoidosis
  4. Eosinophilic pneumonia
  5. Lymphangioleiomyomatosis (LAM) = smooth muscle invades airways, 20-40yo, female, reticular nodular pattern of disease, cysts and pneumothorax.
  6. Pulmonary Langerhan’s cell histiocytosis = proliferation of LC’s from bone marrow, dyspnoea, pneumothorax, stellate nodules, birbeck granules, skin eruptions.
  7. Pulmonary alveolar proteinosis

 

Conditions specifically affecting the interstitium are called interstitial lung diseases.

Extrinsic

  1. Neuromuscular diseases, including quadriplegia
  2. Nonmuscular diseases of the chest wall, e.g. kyphosis

 

Pathophysiology

  1. In disorders that are intrinsic to the lung parenchyma, the underlying process is usually pulmonary fibrosis (scarring of the lung).
  2. As the disease progresses, the normal lung tissue is gradually replaced by scar tissue interspersed with pockets of air.
  3. This can lead to parts of the lung having a honeycomb-like appearance. 
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