Respiratory system and diseases II 2024.PDF

Respiratory system and diseases - II Chronic obstructive pulmonary disease Asthma Lung tumours Learning outcomes ⚫ To have knowledge on causes and risk factors of chronic pulmonary diseases, asthma and lung tumours ⚫ To understand pathogenesis and clinical features of these diseases Respiratory sy...

Respiratory system and diseases - II Chronic obstructive pulmonary disease Asthma Lung tumours Learning outcomes ⚫ To have knowledge on causes and risk factors of chronic pulmonary diseases, asthma and lung tumours ⚫ To understand pathogenesis and clinical features of these diseases Respiratory system and diseases - II Chronic obstructive pulmonary disease Asthma Lung tumours Chronic obstructive pulmonary disease (COPD) Characterised by poorly reversible airflow limitation, usually progressive Associated with a persistent inflammatory response of the lung Predominantly caused by smoking in developed countries A term for patients with airflow obstruction, including chronic bronchitis or emphysema Epidemiology − Develops over many years; rarely symptomatic before middle age − Common in UK, 18% of male smokers, 14% of female smokers; one of leading causes of lost working days Aetiology and pathogenesis Smoking is the dominant causal agent cigarette  smoke macrophages chemotactic factors epithelial cells damage granulocytes proteases Proteases / protease inhibitors imbalance in COPD Atmospheric pollution − a minor role compared to smoking α1-antitrypsin deficiency − a rare cause of early-onset emphysema Pathology Chronic bronchitis: – Chronic inflammation of the airways (predominantly lymphocytes) – Enlargement of mucus-secreting glands of trachea and bronchi – Airway narrowing and hence airflow limitation Emphysema: – Dilatation and destruction of the lung tissue distal to terminal bronchioles – Loss of elastic recoil; expiratory airflow limitation and air trapping Bullous emphysema Clinical features Characteristic symptoms: − − − − Cough Sputum Breathlessness Wheeze Normal COPD Signs: in severe disease: − Tachypnoea − Use of accessory muscles of respiration − Hyperinflation − Poor expansion − Others (cyanosis; cor pulmonale) Investigations Lung function tests: − ↓FEV1 and ↓FEV1/FVC Chest X-ray: − Lungs hyperinflated Arterial blood gases: − Normal or hypoxia and hypercapnia Haemoglobin & PCV may be high ECG or echocardiography: − To assess cardiac status if clinical features of cor pulmonale Treatment, complication & prognosis Treatment: − Smoking cessation − Drug therapy (bronchodiators, corticosteroids, antibiotics etc.) − Treatment of respiratory failure − Other measures (heart failure, secondary polycythaemia) Complications: − Respiratory failure − Cor pulmonale (right heart failure secondary to lung disease) Prognosis: − 50% patients with severe breathlessness die within 5yrs Respiratory system and diseases - II Chronic obstructive pulmonary disease Asthma Lung tumours Asthma A common chronic inflammatory condition of the lungs Hyper-reactivity of the bronchial tree with paroxysmal narrowing of the airways Three characteristics: − Airflow limitation − Airway hyper-responsiveness − Inflammation of the bronchi Airflow limitation often reversible Epidemiology: − The prevalence is increasing; geographical variation: more common in developed countries; much rarer in Far Eastern countries Aetiology Two major factors are involved in the development of asthma: Atopy and allergy: Readily develop IgE against common environmental antigens; genetic and environmental factors affect IgE levels. Increased responsiveness of the airways of the lung (a fall in FEV1) to stimuli Pathogenesis The primary abnormality: − Narrowing of the airway − Thickening of the airway wall − Secretions within the airway lumen Inflammation − Cellular components: eosinophils, T-lymphocytes, macrophages and mast cells → release inflammatory mediators Remodelling − Structural changes in the airway Precipitating factors Occupational sensitizers: − Over 200 materials encountered at workplace may give rise to wheezing, which typically improves on days off - occupational asthma Non-specific factors which may cause wheeze: − e.g., viral infections, cold air, exercise, irritant dusts, vapours and fumes, emotion and drugs A rare cause of asthma: − The airborne spores of Aspergillus fumagatus (a soil mould) Clinical features Wheezing attacks Episodic shortness of breath Some have one or two attacks a year; others have chronic symptoms On examination, during attack: − reduced chest expansion, prolonged expiratory time and bilateral expiratory polyphonic wheezes Investigations Diagnosis often made on the history and response to bronchodilators. No single satisfactory diagnostic test for all Lung function tests: − Demonstration of variable airflow limitation ( PEFR or FEV1) Tests for allergy/hypersensitivity: − Airway responsiveness (histamine or methacholine) − Test of allergy (skin-prick tests) − Blood and sputum for eosinophils & Aspergillus antibody Chest X-ray (at diagnosis and repeated only in acute severe attack) Trial of steroids reversibility To those with severe airflow limitation - reversibility (↑FEV1 > 15%) Exercise tests (in children) Treatment Control of extrinsic factors Drug treatment – Bronchodilators ß2-adrenergic agonists Antimuscarinic bronchodilators Theophyllines – Anti-inflammatory agents Steroids Chromones Leukotriene receptor antagonists Immunosuppressive agents Respiratory system and diseases - II Chronic obstructive pulmonary disease Asthma Lung tumours Lung tumours Lung tumours are common Primary Secondary Primary carcinoma of the lung (bronchial carcinoma) Accounts for 95% of all primary tumours of the lung Most common malignant tumour in the world Poor prognosis − 5 year survival rate