Diseaseas of the Respiratory system.pdf

Restrictive pulmonary disease & Respiratory failure Pneumoconiosis IPF  Restrictive airway disease There is reduced ability of the lung parenchyma to expand. This might be caused by abnormality in the thoracic cage: e.g. neuromuscular problems,...

Restrictive pulmonary disease & Respiratory failure Pneumoconiosis IPF  Restrictive airway disease There is reduced ability of the lung parenchyma to expand. This might be caused by abnormality in the thoracic cage: e.g. neuromuscular problems, severe obesity, and kyphoscoliosis. Intrinsic pulmonary causes include: acute or chronic interstitial lung disease.  Diffuse interstitial lung disease Causes: 1. Idiopathic interstitial fibrosis: the most common. 2. Occupational and environmental dust: coal, silica, asbestos, organic dust (extrinsic allergic alveolitis. 3. Post infectious. 4. Drugs and toxins. 5. Other: ionizing radiation, sarcoidosis, connective tissue diseases.  Clinical picture of restrictive lung diseases Progressive breathlessness. Cough; non-productive. Chest- X- Ray: patchy opacities especially in the basal areas.  Acute respiratory distress syndrome (ARDS) & acute lung injury (DAD) DAD is the final common pathway for a variety of severe lung injuries. In early DAD, there are hyaline membranes lining alveoli (also called hyaline membrane disease). Interstitial inflammation and fibrosis are seen. High oxygen tensions needed to treat the hypoxia resulting from DAD and its etiologies further potentiates this disease.  Pneumoconiosis A group of lung diseases resulting from inhalation of organic or inorganic dust. Honeycomb lung is the end stage of most of these diseases.  Pneumoconiosis Certain factors will determine type and extent of damage: 1. Physical and chemical properties of the inhaled dust: size & shape of particles, inert vs. antigenic. 2. Concentration. 3. Duration of exposure. 4. The coexistence of other lung diseases.  Coal dust 1. Anthracosis: due to inhalation of soot. Has no clinical effect but blackening of lungs at autopsy. Engulfed by macrophages which may travel to hilar L.Ns  Coal dust Coal workers pneumoconiosis: Inhalation of coal with low silica content. Two stages of the disease:  Coal dust 1. Simple pneumoconiosis: – dust particles are engulfed by macrophages and provoke a local fibrotic reaction → obliteration of peribronchial alveoli and atrophy of bronchial smooth muscle. – Usually affects the upper lobes. 2. Progressive massive fibrosis: – 10- 20 years following exposure. – Massive confluent fibrosis of the upper lobes.  Silicosis Inhalation of silica particles. Engulfment by macrophages. Discrete grayish-black fibrotic nodules. Refractile silica particles are surrounded by rings of fibrosis. Obliteration of lumena of bronchioles and blood vessels with pleural adhesions.  Asbestosis Asbestos is considered as a carcinogenic agent which can predispose to mesothelioma. Asbestos is the general name given to several types of fibrous silicates of magnesium.  Asbestosis The most famous types are: 1. White asbestos: chrysotile; resides in the proximal airways. 2. Blue asbestos: crocidolite; peripheral alveoli. 3. Brown asbestos: amosite; peripheral alveoli. It associated with building industry, shipping, and motor engine industry.  Asbestosis The most important factor in asbestosis is the amount: either large dose in a short period or small doses for longer duration will result in asbestosis. Fibers are partially or completely engulfed by macrophages, coated by iron and proteins. They appear as drum sticks.  Asbestosis Fibrosis starts peripherally and basally then progress proximally. Complications of pneumoconiosis: 1. Secondary T.B; except asbestosis. 2. Respiratory failure. 3. Rt heart hypertrophy and failure.  Extrinsic allergic alveolitis Due to inhalation of organic dust → local Arthurs reaction i.e. type III HsR. Examples: Farmers lung and Bird fancier’s disease. Clinically presents as episodes of fever, malaise, dyspnea, and basal crepitations. Repeated exposure might induce lung fibrosis and end stage honeycomb lung.  Idiopathic pulmonary fibrosis A diagnosis by exclusion of other causes like extrinsic allergic alveolitis and pneumoconiosis. Occur in stages: 1. Alveolar exudation with edema, hyaline membrane formation and inflammatory infiltrates.  Idiopathic pulmonary fibrosis 2. Interstitial inflammatory infiltration by mixed inflammatory cells. 3. Interstitial fibroblastic proliferation. 4. Progressive obliterative fibrosis with architectural abnormalities.  Idiopathic pulmonary fibrosis Two forms: 1. Usual interstitial pneumonia: – patchy thickening of alveolar walls due to both fibrosis and mixed inflammation. – There is progressive fibrosis. – Patients may eventually die due to respiratory failure.  Idiopathic pulmonary fibrosis 2. Desquamative interstitial pneumonia: – Diffuse. – Alveoli are filled by macrophages with minimal fibrosis. – Prognosis is good. – Patients respond to corticosteroid therapy.  Respiratory failure Addition of O2 and removal of CO2 from the circulating blood is the main function of the respiratory system. Respiratory failure is defined in terms of hypoxemia as arterial oxygen tension