RESTRICTIVE LUNG DISEASE

RESTRICTIVE LUNG DISEASE
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.
Restrictive lung diseases may be divided into the
following groups:

Intrinsic lung diseases (diseases of the lung
parenchyma)

Extrinsic disorders (extra-parenchymal
diseases)
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.
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.
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 exerciseinduced desaturation.
 Hyperventilation at rest secondary to reflex
stimulation.
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.

Diseases of the Lung
Parenchyma
Structure of the Alveolar Wall
EM in Pulmonary Fibrosis
Interstitium
Diffuse Interstitial Pulmonary
Fibrosis

Synonyms: idiopathic pulmonary fibrosis, interstitial
pneumonia, cryptogenic fibrosing alveolitis.
Pathology
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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
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.
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.

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.

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.
Treatment
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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.
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.

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.
Non-caseating granulomas
in Sarcoidosis
Stage I
(bilateral hilar adenopathy)
Stage II
Reticular nodules and BHL
HRCT – subpleural nodules
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 PFT’s –
treatment recommended.
 Prednisone 0.5- 1 mg/kg initially, then tapered
and continued for 6 months to 1 year.
Hypersensitivity Pneumonitis
Also known as extrinsic allergic alveolitis.
 Hypersensitivity reaction in the lung occurs in
response to inhaled organic dust.
 Example is farmer’s lung.
 The exposure may be occupational or
environmental.
 The disease occurs from type III and type IV
hypersensitivity reactions.
 Farmer’s lung is due to thermophilic
actinomyces in moldy hay.
 Bird fancier’s lung is caused by avian antigen.
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Pathology
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There is infiltration of alveolar walls with
lymphocytes, plasma cells and histiocytes.
There are loosely formed granulomas.
Fibrotic changes occur in advanced disease.
Clinical Features

The disease may occur in acute or chronic forms.
Acute HP
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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.
HRCT in Acute HP
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.

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.

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.

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
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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.
Neuromuscular Disorders
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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.
PFT’s 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.