Diseases of the Respiratory System PDF

Diseases of The Respiratory System: Developmental Anomalies: Include: - Agenesis or hypoplasia of both lungs, one lung, or single lobes. - Tracheal and bronchial anomalies (atresia, stenosis, tracheoesophageal fistula). - Vascular anomalies. - Congenital lobar overinflation (emphysema)....

Diseases of The Respiratory System: Developmental Anomalies: Include: - Agenesis or hypoplasia of both lungs, one lung, or single lobes. - Tracheal and bronchial anomalies (atresia, stenosis, tracheoesophageal fistula). - Vascular anomalies. - Congenital lobar overinflation (emphysema). - Foregut cysts. - Congenital pulmonary airway malformation. - Pulmonary sequestrations. Atelectasis: Refers to collapse of lung tissue producing an airless lung parenchyma. It could be inherited or acquired. Acquired atelectasis can be subdivided into: 1. Resorption (obstructive) atelectasis is the consequence of complete obstruction of an airway, which in time leads to resorption of the oxygen trapped in the dependent alveoli, without impairment of blood flow through the affected alveolar walls. 2. Compression atelectasis results whenever the pleural cavity is partially or completely filled by fluid exudates (pleural effusion), tumor, blood (hæmothorax), or air (pneumothorax). 3. Contraction atelectasis occurs when local or generalized fibrotic changes in the lung or pleura prevent full expansion. Significant atelectasis reduces oxygenation and predisposes to infection. Atelectasis is a reversible disorder (except that caused by contraction). Pulmonary Œdema: Causes: 1. Hemodynamic: - Increased hydrostatic pressure (increased pulmonary venous pressure) Left-sided heart failure (common) Volume overload Pulmonary vein obstruction - Decreased oncotic pressure (less common) Hypoalbuminemia Nephrotic syndrome Liver disease Protein-losing enteropathies - Lymphatic obstruction (rare) 2. Microvascular injury (alveolar injury): - Infections: pneumonia, septicemia - Inhaled gases: oxygen, smoke - Liquid aspiration: gastric contents, near-drowning - Drugs and chemicals: chemotherapeutic agents (bleomycin), other medications (amphotericin B), heroin, kerosene, paraquat - Shock, trauma  - Radiation - Transfusion related 3. Unknown: - High altitude - Neurogenic (central nervous system trauma) Acute Respiratory Distress Syndrome (ARDS) and Diffuse Alveolar Damage (DAD): ARDS is a clinical syndrome caused by diffuse alveolar capillary damage, with rapid onset of severe life-threatening respiratory insufficiency, cyanosis, and severe arterial hypoxemia refractory to oxygen therapy that may progress to extrapulmonary multisystem organ failure. Causes: 1. Infection Sepsis Diffuse pulmonary infections Viral, Mycoplasma, and Pneumocystis pneumonia; miliary tuberculosis Gastric aspiration 2. Physical/Injury Mechanical trauma, including head injuries Pulmonary contusions Near-drowning Fractures with fat embolism Burns Ionizing radiation 3. Inhaled Irritants Oxygen toxicity Smoke Irritant gases and chemicals 4. Chemical Injury Heroin or methadone overdose Acetylsalicylic acid Barbiturate overdose Paraquat 5. Hematologic Conditions Multiple transfusions Disseminated intravascular coagulation 6. Pancreatitis 7. Uremia 8. Cardiopulmonary Bypass 9. Hypersensitivity Reactions Organic solvents Drugs Obstructive Pulmonary Diseases: Include emphysema, chronic bronchitis, asthma, and bronchiectasis. Both emphysema and chronic bronchitis are often grouped together under the term "chronic obstructive pulmonary disease-COPD".  Anatomic Major Pathologic Clinical Term Site Changes Ætiology Signs/Symptoms Chronic bronchitis Bronchus Mucous gland Tobacco smoke, air Cough, sputum hyperplasia, pollutants production hypersecretion Bronchiectasis Bronchus Airway dilation and Persistent or severe Cough, purulent scarring infections sputum, fever Asthma Bronchus Smooth muscle Immunologic or Episodic wheezing, hyperplasia, excess undefined causes cough, dyspnœa mucus, inflammation Emphysema Acinus Airspace enlargement; Tobacco smoke Dyspnœa (alveoli) wall destruction Emphysema: Is a condition of the lung characterized by abnormal permanent enlargement of the airspaces distal to the terminal bronchiole, accompanied by destruction of their walls without obvious fibrosis. Four pathologic variants are recognized: centriacinar, panacinar (panlobular), distal acinar (paraseptal) and irregular. Death in most patients with is due to (1) respiratory acidosis and coma, (2) right-sided heart failure, and (3) massive collapse of the lungs secondary to pneumothorax. Treatment options include bronchodilators, steroids, bullectomy, and in selected patients, lung volume reduction surgery and lung transplantation. Chronic bronchitis: It is present in any patient who has persistent cough with sputum production for at least 3 months in at least 2 consecutive years, in the absence of any other identifiable cause. It is so common among habitual smokers and inhabitants of smog-laden cities. When persistent for years, it may (1) progress to chronic obstructive airway disease, (2) lead to cor pulmonale and heart failure, or (3) cause atypical metaplasia and dysplasia of the respiratory epithelium, with malignant transformation. The key pathological change is mucus hypersecretion caused by hyperplasia of submucous glands and goblet cells. Histologically: 1. Goblet cell metaplasia with mucus plugging of the lumen. 2. Clustering of alveolar macrophages. 3. Inflammatory infiltration. 4. Fibrosis of the bronchiolar wall. Asthma: Is a chronic inflammatory disorder of the airways that causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough, particularly at night and/or in the early morning, usually associated with reversible bronchoconstriction and airflow limitation. It is thought that inflammation causes an increase in airway responsiveness (bronchospasm) to a variety of stimuli, including extrinsic (allergic) and intrinsic (nonimmune). Asthma can be classified into:  1. Atopic asthma: seen mainly during childhood and precipitated by allaergic reactions. 2. Non-atopic asthma: caused by viral infections of the respiratory mucosa. 3. Drug-induced asthma: e.g. aspirin-induced asthma. 4. Occupational asthma: precipitated by fumes (epoxy, resins, plastics). Bronchiectasis: Is characterized by permanent dilation of bronchi and bronchioles caused by destruction of the muscle and elastic tissue, resulting from or associated with chronic necrotizing infections. It is encountered in: 1. Congenital or hereditary conditions: cystic fibrosis, lung sequestration, immotile cilia syndrome. 2. Postinfectious conditions: TB, Aspergillosis, Staphylococcal pneumonia. 3. Bronchial obstruction by tumour, foreign bodies or mucus plugs. 4. Autoimmune: Rheumatoid arthritis, inflammatory bowel diseases, SLE. Pulmonary Infections: Upper respiratory tract infections are the most common infections allover the body (pharyngitis and common cold). Lower respiratory tract infections (pneumonias) can be predisposed by: 1. Loss or suppression of the cough reflex (coma, anæsthesia). 2. Injury to the mucociliary apparatus (smoke, corrosives and gases). 3. Interference with the phagocytic or bactericidal action of alveolar macrophages (alcohol, smoke, anoxia). 4. Pulmonary congestion and edema. 5. Accumulation of secretions (cystic fibrosis). Bacterial pneumonia has two pathological patterns; bronchopneumonia with lobular distribution and lobar pneumonia. In lobar pneumonia four stages are seen: congestion, red hepatization, grey hepatization and resolution. Some times pleuritis can follow pneumonitis. Other complications include: abscess formation, organization of infection, bacteræmia. Tumours: Is currently the most frequently diagnosed major cancer in the world and the most common cause of cancer mortality. Risk Factors: Include: 1. Cigarette smoking: Increase the risk by about 10 folds. The development of cancers is proportionate to the amount of daily smoking, tendency to inhale and the duration of smoking. 2. Industrial hazards: ionizing radiation and asbestos. 3. Atmospheric pollutants. Pathological variants: 1. Squamous cell carcinoma (25-40%). 2. Adenocarcinoma (25-40%). 3. Small cell carcinoma (20-25%). 4. Large cell carcinoma (10-15%).