RESTRICTIVE LUNG DISEASE

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RESTRICTIVE LUNG DISEASE

• ssharma.com
• By Sat Sharma
• Assistant Professor
• University of Manitoba

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Background

• The lung volumes are reduced either because of
• 1. Alteration in lung parenchyma.
• 2. Diseases of the pleura, chest wall or
  neuromuscular
• apparatus.
• Physiologically restrictive lung diseases are
  defined by reduced total lung capacity, vital
  capacity and functional residual capacity, but
  with preserved air flow.

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• Restrictive lung diseases may be divided into the
  following groups
• Intrinsic lung diseases (diseases of the lung
  parenchyma)
• Extrinsic disorders (extra-parenchymal diseases)

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Intrinsic Lung Diseases

• These diseases cause either
• Inflammation and/or scarring of lung tissue
  (interstitial lung disease)
• or
• Fill the air spaces with exudate and debris
  (pneumonitis).
• These diseases are classified further according
  to the etiological factor.

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Extrinsic Disorders

• The chest wall, pleura and respiratory muscles
  are the components of respiratory pump.
• Disorders of these structures will cause lung
  restriction and impair ventilatory function.
• These are grouped as
• Non-muscular diseases of the chest wall.
• Neuromuscular disorders.

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Pathophysiology

• Intrinsic lung diseases
• Diffuse parenchymal disorders cause reduction in
  all lung volumes.
• This is produced by excessive elastic recoil of
  the lungs.
• Expiratory flows are reduced in proportion to
  lung volumes.
• Arterial hypoxemia is caused by
  ventilation/perfusion mismatch.
• Impaired diffusion of oxygen will cause
  exercise-induced desaturation.
• Hyperventilation at rest secondary to reflex
  stimulation.

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Extrinsic Disorders

• Diseases of the pleura, thoracic cage, decrease
  compliance of respiratory system.
• There is reduction in lung volumes.
• Secondarily, atelectasis occurs leading to V/Q
  mismatch ? hypoxemia.
• The thoracic cage and neuromuscular structures
  are a part of respiratory system.
• Any disease of these structures will cause
  restrictive disease and ventilatory dysfunction.

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Diseases of the Lung Parenchyma
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Structure of the Alveolar Wall
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EM in Pulmonary Fibrosis
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Interstitium
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Diffuse Interstitial Pulmonary Fibrosis

• Synonyms idiopathic pulmonary fibrosis,
  interstitial pneumonia, cryptogenic fibrosing
  alveolitis.
• Pathology
• Thickening of interstitium.
• Initially, infiltration with lymphocytes and
  plasma cells.
• Later fibroblasts lay down thick collagen
  bundles.
• These changes occur irregularly within the lung.
• Eventually alveolar architecture is destroyed
  honeycomb lung

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• Etiology
• Unknown, may be immunological reaction.
• Clinical Features
• Uncommon disease, affects adults in late middle
  age.
• Progressive exertional dyspnea, later at rest.
• Non-productive cough.
• Physical examination shows finger clubbing, fine
  inspiratory crackles throughout both lungs.
• Patient may develop respiratory failure
  terminally.
• The disease progresses insidiously, median
  survival 4-6 years.

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Pulmonary Function

• Spirometry reveals a restrictive pattern. FVC is
  reduced, but FEV1/FVC supernormal.
• All lung volumes TLC, FRC, RV are reduced.
• Pressure volume curve of the lung is displaced
  downward and flattened.

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Gas Exchange

• Arterial PaO2 and PaCO2 are reduced, pH normal.
• On exercise PaO2 decreases dramatically.
• Physiologic dead space and physiologic shunt and
  VQ mismatch are increased.
• Diffuse impairment contributes to hypoxemia on
  exercise.
• There is marked reduction in diffusing capacity
  due to thickening of blood gas barrier and VQ
  mismatch.

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Diagnosis

• Diagnosis is often suggested by history, chest
  radiograph and high resolution CT scan of the
  lungs.
• If old chest x-rays show classical disease,
  absence of other disease processes on history and
  no occupational or environmental exposure
  clinical diagnosis can be made.
• In other cases a surgical lung biopsy is obtained.

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Treatment

• Each patient is individually assessed.
• Patients are treated if they have symptoms or
  progressive dysfunction on pulmonary function
  tests.
• Corticosteroids (Prednisone 1 mg/kg) is standard
  therapy.
• Prednisone dose is lowered over 6-8 weeks and
  continued at 15 mg for 1-2 years.
• Addition of Imuran may benefit survival.
• Cyclophosphamide occasionally used.
• Antifibrotics such as colchicine may be used.
• Ancillary therapies such as oxygen,
  rehabilitation, psychosocial aspects are helpful.

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Sarcoidosis

• A disease characterized by the presence of
  granulomatous tissue.
• This is a systemic disease which involves eyes,
  brain, heart, lungs, bones and kidneys, skin,
  liver and spleen.
• On pathology a non-caseating granuloma composed
  of histiocytes, giant cells and lymphocytes.
• In advanced lung disease fibrotic changes are
  seen.

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Etiology

• Unknown, likely immunological basis.
• Clinical Features
• Four stages are identified
• Stage 0 No obvious intrathoracic involvement
• Stage 1 Bilateral hilar lymphadenopathy, often
  accompanied by arthritis, uveitis and erythema
  nodosum.
• Stage 2 Pulmonary parenchyma is also involved,
  changes in mid and upper zones.
• Stage 3 Pulmonary infiltrates and fibrosis
  without adenopathy.

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Non-caseating granulomasin Sarcoidosis
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Stage I (bilateral hilar adenopathy)
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Stage IIReticular nodules and BHL
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HRCT subpleural nodules
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• Pulmonary Function
• No impairment occurs in stages 0 and 1.
• In stages 2 and 3 restrictive changes are seen.
• Treatment and Prognosis
• 85 of these patients improve spontaneously, but
  15 may develop progressive fibrosis and
  respiratory failure.
• Treatment is other observation, but in
  symptomatic patients or deteriorating PFTs
  treatment recommended.
• Prednisone 0.5- 1 mg/kg initially, then tapered
  and continued for 6 months to 1 year.

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Hypersensitivity Pneumonitis

• Also known as extrinsic allergic alveolitis.
• Hypersensitivity reaction in the lung occurs in
  response to inhaled organic dust.
• Example is farmers lung.
• The exposure may be occupational or
  environmental.
• The disease occurs from type III and type IV
  hypersensitivity reactions.
• Farmers lung is due to thermophilic actinomyces
  in moldy hay.
• Bird fanciers lung is caused by avian antigen.

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• Pathology
• There is infiltration of alveolar walls with
  lymphocytes, plasma cells and histiocytes.
• There are loosely formed granulomas.
• Fibrotic changes occur in advanced disease.

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Clinical Features

• The disease may occur in acute or chronic forms.
• Acute HP
• Dyspnea, fever, malaise and cough appear 4-6
  hours after exposure.
• These symptoms continue for 24-48 hours.
• Physical examination shows fine crackles
  throughout the lungs.
• These patients present with progressive dyspnea
  over a period of years.
• Chest radiograph may be normal, but may show
  reticular nodular infiltration.

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HRCT in Acute HP
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• Chronic HP
• These patients present with progressive dyspnea.
• Physical examination shows bilateral inspiratory
  crackles.
• Chest x-ray shows reticular nodular infiltration
  and fibrosis predominantly in upper lobes.
• Pulmonary function tests restrictive pattern.
• Gas exchange shows hypoxemia which worsens on
  exercise.

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Interstitial Disease Caused by Drugs, Poisons and
Radiation

• Various drugs cause acute pulmonary reaction
  proceeding to interstitial fibrosis.
• These drugs are busulfan, nitrofurantoin,
  amiodarone, bleomycin.
• High oxygen concentration interstitial
  fibrosis.
• Radiation exposure acute pneumonitis
  fibrosis.

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Collagen Vascular Diseases

• Several collagen vascular diseases particularly
  systemic sclerosis and lupus and rheumatoid
  arthritis may lead to systemic sclerosis.
• Dyspnea is often severe.
• A definite diagnosis requires surgical lung
  biopsy.
• Treatment is corticosteroids plus cytotoxic
  therapy.

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Pleural Diseases

• Pneumothorax could be either primary or
  secondary.
• Pleural effusion can be acute or chronic.
• Pleural effusion is divided into exudate and
  transudate.
• Pleural thickening longstanding pleural
  effusion results in fibrotic pleura which splints
  the lung and prevents its expansion.
• If the disease is bilateral may cause
  restrictive lung diease.
• Treatment may be decortication.

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Diseases of the Chest Wall

• Deformity of thoracic cage such as kyphoscoliosis
  and ankylosing spondylitis.
• Scoliosis lateral curvature of spine, kyphosis
  posterior curvature.
• Cause is unknown, polio and previous
  tuberculosis.
• Patients develop exertional dyspnea, rapid
  shallow breathing.
• Hypoxemia, hypercapnia and cor-pulmonale
  supervene.
• Pulmonary function tests show RVP with normal
  diffusion.
• Cause of death is respiratory failure or
  intracurrent pulmonary infection.
• Treatment is non-invasive or invasive chronic
  ventilation.

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Neuromuscular Disorders

• Diseases affecting muscles of respiration or
  their nerve supply.
• Poliomyelitis, Guillain-Barre syndrome, ALS,
  myasthenia gravis, muscular dystrophies.
• All these lead to dyspnea and respiratory
  failure.
• PFTs show reduced FVC, TLC and FEV1.
• The progress of disease can be monitored by FVC
  and blood gases.
• Maximal inspiratory and expiratory pressures are
  reduced.
• Treatment is either treating the underlying cause
  or assisted ventilation.

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RESTRICTIVE LUNG DISEASE

• ssharma.com
• By Sat Sharma
• Assistant Professor
• University of Manitoba