Major Topics in Respiratory Medicine - Quick Overview

1. Anatomy & Physiology of the Respiratory System

• Airways: trachea, bronchi, bronchioles, alveoli
• Pulmonary circulation vs. bronchial circulation
• Lung volumes: TLC, FRC, RV, VC, FEV1, FVC
• Gas exchange: V/Q matching, diffusion, dead space
• Mechanics: compliance, airway resistance, work of breathing
• Respiratory muscles: diaphragm, intercostals, accessory muscles
• Control of breathing: central (medullary), peripheral chemoreceptors

2. Obstructive Lung Diseases

Asthma

• Chronic airway inflammation with reversible bronchoconstriction
• Triggers: allergens, exercise, cold air, infections
• Pathology: eosinophilic inflammation, smooth muscle hypertrophy, mucus plugging
• Diagnosis: spirometry (FEV1/FVC < 0.70, reversibility >12% with bronchodilator)
• Management: stepwise - SABA, ICS, ICS+LABA, biologics (anti-IL-5, anti-IgE)

COPD

• Predominantly caused by smoking; irreversible airflow limitation
• Subtypes: chronic bronchitis (productive cough >3 months x 2 years) and emphysema (alveolar destruction)
• Spirometric diagnosis: post-bronchodilator FEV1/FVC < 0.70
• GOLD staging (I-IV) by FEV1% predicted
• Management: smoking cessation, SABA/LAMA/LABA, ICS (in frequent exacerbators), pulmonary rehab, oxygen therapy, lung volume reduction

Bronchiectasis

• Permanent abnormal bronchial dilatation from repeated infection/inflammation
• Causes: post-infectious, cystic fibrosis, primary ciliary dyskinesia, immune deficiency
• Feature: daily productive cough, recurrent exacerbations
• CT chest: classic "signet ring" sign

3. Respiratory Infections

Pneumonia

• Community-acquired (CAP): Streptococcus pneumoniae (most common), atypicals (Mycoplasma, Legionella, Chlamydia)
• Hospital-acquired (HAP/VAP): gram-negatives (Pseudomonas, Klebsiella), MRSA
• Severity scoring: CURB-65 (Confusion, Urea >7, RR ≥30, BP <90/60, age ≥65)
• CXR: lobar consolidation (typical), bilateral patchy infiltrates (atypical/viral)

Tuberculosis (TB)

• Mycobacterium tuberculosis; spread by aerosol
• Primary vs. reactivation TB; miliary TB
• Diagnosis: Mantoux test, IGRA, sputum AFB smear/culture, GeneXpert
• Treatment: RIPE (Rifampicin, Isoniazid, Pyrazinamide, Ethambutol) x 2 months, then RI x 4 months

COVID-19 / Viral pneumonitis

• SARS-CoV-2, cytokine storm, organizing pneumonia pattern on CT

4. Pulmonary Vascular Disease

Pulmonary Embolism (PE)

• Deep vein thrombosis -> embolism to pulmonary arteries
• Risk: Virchow's triad (stasis, hypercoagulability, endothelial injury)
• Presentation: pleuritic chest pain, dyspnea, hemoptysis, hypoxia
• Wells score for pre-test probability; D-dimer; CTPA (gold standard)
• Management: anticoagulation (LMWH/DOACs), thrombolysis for massive PE

Pulmonary Hypertension (PH)

• mPAP >20 mmHg at rest
• Groups 1-5 (WHO classification): PAH, left heart disease, lung disease, CTEPH, miscellaneous
• Group 1 (PAH): idiopathic, heritable, drug-induced
• Treatments: PDE-5 inhibitors (sildenafil), endothelin antagonists (bosentan), prostacyclins

5. Interstitial Lung Diseases (ILD)

• Heterogeneous group of diffuse parenchymal lung diseases
• Key patterns on HRCT: UIP, NSIP, DIP, COP, AIP
• Idiopathic Pulmonary Fibrosis (IPF): most common ILD; UIP pattern; anti-fibrotics (nintedanib, pirfenidone)
• Sarcoidosis: non-caseating granulomas; bilateral hilar lymphadenopathy; lung, skin, eye involvement
• Hypersensitivity Pneumonitis: antigen-driven; farmer's lung, bird fancier's lung
• Connective tissue disease-ILD: RA, SSc, SLE, polymyositis
• Restrictive pattern on PFTs: reduced TLC, FVC, with normal FEV1/FVC

6. Lung Cancer

• Leading cause of cancer death worldwide
• Types:
  • Non-Small Cell (NSCLC, 85%): Adenocarcinoma (most common, peripheral), Squamous cell (central, cavitating), Large cell
  • Small Cell (SCLC, 15%): central, rapid growth, early metastasis, paraneoplastic syndromes (SIADH, Cushing's, Lambert-Eaton)
• Risk factors: smoking (most important), radon, asbestos, occupational exposures
• Staging: TNM for NSCLC; limited vs. extensive for SCLC
• Diagnostics: CT chest, PET scan, bronchoscopy + biopsy, EBUS
• Treatment: surgery (early NSCLC), chemo-radiation, targeted therapy (EGFR, ALK, ROS1 mutations), immunotherapy (PD-L1/PD-1 inhibitors)
• Paraneoplastic syndromes: hypertrophic pulmonary osteoarthropathy, digital clubbing, SIADH

7. Pleural Diseases

Pleural Effusion

• Transudate (Light's criteria: protein <0.5 ratio, LDH <0.6 ratio): heart failure, cirrhosis, nephrotic syndrome
• Exudate: pneumonia (parapneumonic), malignancy, TB, PE
• Diagnosis: thoracocentesis; pleural fluid analysis (pH, glucose, LDH, protein, cytology, culture)

Pneumothorax

• Primary spontaneous (tall, thin young males), Secondary (COPD, CF, Marfan's)
• Tension pneumothorax: medical emergency - tracheal deviation, absent breath sounds, hypotension
• Management: aspiration, chest drain, pleurodesis for recurrent cases

Mesothelioma

• Malignant pleural tumor; strongly linked to asbestos exposure
• Long latency (20-40 years); poor prognosis

8. Respiratory Failure

ARDS (Acute Respiratory Distress Syndrome)

• Berlin definition: acute onset, bilateral infiltrates, PaO2/FiO2 <300, not cardiac
• Management: low tidal volume ventilation (6 ml/kg IBW), prone positioning, conservative fluids

9. Sleep-Related Breathing Disorders

• Obstructive Sleep Apnoea (OSA): repetitive upper airway collapse during sleep
  • Risk: obesity, retrognathia, large neck
  • Diagnosis: polysomnography (AHI ≥5)
  • Treatment: weight loss, CPAP (first-line), mandibular advancement device
• Central Sleep Apnoea: lack of respiratory drive (Cheyne-Stokes in heart failure)

10. Occupational & Environmental Lung Diseases

• Pneumoconioses: dust inhalation
  • Silicosis (silica), Asbestosis (asbestos), Coal worker's pneumoconiosis
• Asthma: occupational triggers (isocyanates, latex, flour)
• COPD: biomass fuel smoke, occupational dusts

11. Pulmonary Function Tests (PFTs) - Key Concepts

• Spirometry, Diffusion capacity (DLCO), Plethysmography, 6-minute walk test

12. Key Investigations in Respiratory Medicine

13. Respiratory Emergencies

• Acute severe asthma / Status asthmaticus
• Tension pneumothorax
• Massive pulmonary embolism
• ARDS
• Acute exacerbation of COPD (AECOPD)
• Haemoptysis (massive)

Sources: Murray & Nadel's Textbook of Respiratory Medicine (2-Volume) and Fishman's Pulmonary Diseases and Disorders (2-Volume Set) - both available in the medical library.