Respiratory Diseases and Disorders

Restrictive Pulmonary Disease

• Reduced lung parenchyma expansion due to thoracic cage abnormalities (neuromuscular problems, severe obesity, kyphoscoliosis) or intrinsic pulmonary causes (interstitial lung disease)

Causes of Restrictive Lung Disease

• Idiopathic interstitial fibrosis (most common)
• Occupational and environmental dust (coal, silica, asbestos, organic dust)
• Post-infectious
• Drugs and toxins
• Ionizing radiation, sarcoidosis, connective tissue diseases

Clinical Picture of Restrictive Lung Disease

• Progressive breathlessness
• Non-productive cough
• Chest X-ray shows patchy opacities in basal areas

Acute Respiratory Distress Syndrome (ARDS) and Acute Lung Injury (DAD)

• Final common pathway for severe lung injuries
• Hyaline membranes lining alveoli in early DAD
• Interstitial inflammation and fibrosis
• High oxygen tensions needed to treat hypoxia, which can potentiate the disease

Pneumoconiosis

• Group of lung diseases resulting from inhalation of organic or inorganic dust
• Honeycomb lung is the end stage of most pneumoconiosis
• Factors determining type and extent of damage: physical and chemical properties of inhaled dust, concentration, duration of exposure, coexistence of other lung diseases

Coal Workers' Pneumoconiosis

• Inhalation of coal with low silica content
• Two stages: simple pneumoconiosis and progressive massive fibrosis
• Simple pneumoconiosis: dust particles engulfed by macrophages, local fibrotic reaction, obliteration of peribronchial alveoli and atrophy of bronchial smooth muscle
• Progressive massive fibrosis: massive confluent fibrosis of upper lobes, 10-20 years following exposure

Silicosis

• Inhalation of silica particles
• Engulfment by macrophages
• Discrete grayish-black fibrotic nodules
• Refractile silica particles surrounded by rings of fibrosis
• Obliteration of lumena of bronchioles and blood vessels with pleural adhesions

Asbestosis

• Inhalation of asbestos particles
• Asbestos is a carcinogenic agent, predisposing to mesothelioma
• Most famous types: white asbestos (chrysotile), blue asbestos (crocidolite), brown asbestos (amosite)
• Associated with building industry, shipping, and motor engine industry
• Amount of asbestos inhaled is the most important factor
• Fibers partially or completely engulfed by macrophages, coated by iron and proteins, appearing as drum sticks

Complications of Pneumoconiosis

• Secondary T.B (except asbestosis)
• Respiratory failure
• Right heart hypertrophy and failure

Extrinsic Allergic Alveolitis

• Due to inhalation of organic dust, causing local Arthus reaction (type III hypersensitivity reaction)
• Examples: Farmers' lung and Bird fancier's disease
• Clinically presents as episodes of fever, malaise, dyspnea, and basal crepitations
• Repeated exposure may induce lung fibrosis and end-stage honeycomb lung

Idiopathic Pulmonary Fibrosis

• Diagnosis by exclusion of other causes like extrinsic allergic alveolitis and pneumoconiosis
• Occurs in stages: alveolar exudation, interstitial inflammatory infiltration, interstitial fibroblastic proliferation, and progressive obliterative fibrosis
• Two forms: usual interstitial pneumonia and desquamative interstitial pneumonia

Respiratory Failure

• Defined as hypoxemia with arterial oxygen tension <60 mmHg
• Addition of O2 and removal of CO2 from circulating blood is the main function of the respiratory system

Learn about restrictive pulmonary diseases, respiratory failure, pneumoconiosis, and idiopathic pulmonary fibrosis, including causes and effects on the lung parenchyma and thoracic cage.