Master Respiratory
for PLAB 1

Core Concepts

The respiratory system facilitates gas exchange (oxygen uptake, carbon dioxide removal). Key components include airways (nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles) and alveoli. Common respiratory pathologies for PLAB 1 include obstructive lung diseases (Asthma, COPD, Bronchiectasis), restrictive lung diseases (Pulmonary Fibrosis, ILDs), infections (Pneumonia, Tuberculosis), vascular conditions (Pulmonary Embolism, Pulmonary Hypertension), pleural diseases (Pneumothorax, Pleural Effusion), and malignancy (Lung Cancer). Understanding airway patency, lung volumes, gas exchange principles, and inflammation is crucial.

Clinical Presentation

• Dyspnoea (SOB): Common in most conditions (Asthma, COPD, Pneumonia, PE, HF). Can be acute or chronic, exertional or at rest.
• Cough:
  • Productive: Sputum (colour, consistency – e.g., yellow/green in infection, rusty in Strep. pneumo., frothy pink in pulmonary oedema). Common in Bronchitis, Pneumonia, Bronchiectasis.
  • Non-productive (dry): Asthma, ILD, GORD, ACE inhibitors.
  • Persistent: >8 weeks, consider asthma, GORD, post-nasal drip, lung cancer, TB.
• Chest Pain:
  • Pleuritic: Sharp, worse on inspiration/cough. Common in Pneumonia, PE, Pneumothorax, Pleurisy.
  • Non-pleuritic: Dull ache, tightness. Common in Angina, MI, Oesophagitis, Musculoskeletal.
• Wheeze: High-pitched whistling, expiratory. Common in Asthma, COPD, Bronchiolitis, foreign body aspiration.
• Haemoptysis: Coughing up blood. Can range from blood-streaked sputum to frank blood. Serious causes: Lung cancer, TB, Bronchiectasis, PE, Pulmonary oedema.
• Stridor: High-pitched inspiratory sound due to upper airway obstruction (larynx/trachea). Epiglottitis, foreign body, laryngeal oedema.
• Systemic Symptoms: Fever (infection), Weight loss (malignancy, TB), Night sweats (TB, lymphoma).
• Signs on Examination:
  • Respiratory rate (tachypnoea/bradypnoea), accessory muscle use, cyanosis.
  • Tracheal deviation (tension pneumothorax, large pleural effusion).
  • Chest expansion (reduced in consolidation, fibrosis, effusion).
  • Percussion: Dull (consolidation, effusion), Hyper-resonant (pneumothorax, emphysema).
  • Auscultation:
    • Wheeze: Asthma, COPD.
    • Crackles (crepitations): Fine (pulmonary fibrosis, HF), Coarse (pneumonia, bronchiectasis).
    • Diminished/Absent breath sounds: Pneumothorax, Pleural effusion, Lobar collapse.
    • Bronchial breathing: Consolidation.
    • Pleural rub: Pleurisy, PE.
  • Clubbing: Lung cancer, bronchiectasis, CF, ILD.

Diagnosis (Gold Standard)

• General Investigations:
  • CXR: Initial imaging for most respiratory complaints (pneumonia, pneumothorax, effusion, cancer).
  • Spirometry: Essential for diagnosing and monitoring obstructive (Asthma, COPD) and restrictive lung diseases. FEV1/FVC ratio is key.
  • Arterial Blood Gas (ABG): Assess oxygenation, ventilation, and acid-base status (ARDS, COPD exacerbation, severe asthma).
  • Sputum Culture & Sensitivity: Identify pathogens in productive coughs (pneumonia, bronchiectasis, TB).
  • Full Blood Count (FBC): Assess for anaemia, infection markers (leukocytosis), eosinophilia (asthma).
  • CRP/ESR: Inflammatory markers.
• Specific Conditions:
  • Asthma: Reversible obstructive pattern on spirometry (FEV1/FVC <0.7, >12% and >200ml reversibility with bronchodilator) AND/OR positive FeNO or bronchial challenge test.
  • COPD: Irreversible obstructive pattern on spirometry (FEV1/FVC <0.7 post-bronchodilator).
  • Pneumonia: CXR showing consolidation.
  • Tuberculosis (TB): Sputum smear (Acid-Fast Bacilli) and culture (Mycobacterium tuberculosis).
  • Pulmonary Embolism (PE): CT Pulmonary Angiogram (CTPA) in stable patients. V/Q scan if CTPA contraindicated. D-dimer for exclusion in low-risk patients.
  • Pneumothorax: CXR (visualisation of visceral pleural line).
  • Pleural Effusion: CXR/Ultrasound (fluid in pleural space), confirmed by diagnostic thoracentesis and fluid analysis (Exudate vs Transudate using Light's criteria).
  • Lung Cancer: Tissue biopsy (bronchoscopy, CT-guided, EBUS) for histology. Staging with CT, PET-CT.
  • Interstitial Lung Disease (ILD)/Pulmonary Fibrosis: High-Resolution CT (HRCT) chest (e.g., honeycombing in IPF), +/- lung biopsy.

Management (First Line)

• Asthma:
  • Mild/Moderate: SABA (Salbutamol) as reliever. Add low-dose ICS (Beclomethasone) if symptoms >3 times/week or nocturnal. Step up to LABA/ICS combo if needed.
  • Acute Exacerbation: O2, high-dose SABA, Ipratropium Bromide, systemic corticosteroids (Prednisolone), consider IV Magnesium Sulfate for severe.
• COPD:
  • SABA/SAMA (Ipratropium) as reliever. Long-acting bronchodilators (LABA e.g., Salmeterol, LAMA e.g., Tiotropium) for symptomatic relief. ICS/LABA/LAMA for severe disease with exacerbations.
  • Acute Exacerbation: O2 (titrate to SaO2 88-92% if CO2 retainer), bronchodilators, systemic corticosteroids, antibiotics (if infective signs), consider NIV.
• Pneumonia:
  • Community Acquired (CAP): Amoxicillin (first-line for low severity). Macrolide (Clarithromycin) or Doxycycline if penicillin allergic or atypical suspected. Adjust based on CURB-65 severity score.
  • Hospital Acquired (HAP): Broader spectrum antibiotics (e.g., Piperacillin/Tazobactam).
• Tuberculosis (TB): Multi-drug regimen: RIPE (Rifampicin, Isoniazid, Pyrazinamide, Ethambutol) for 2 months, followed by Rifampicin and Isoniazid for 4 months. DOT (Directly Observed Therapy) often used.
• Pulmonary Embolism (PE):
  • Anticoagulation: Low Molecular Weight Heparin (LMWH) initiated immediately, followed by long-term DOAC (Apixaban, Rivaroxaban) or Warfarin.
  • Thrombolysis: For massive PE with haemodynamic instability.
• Pneumothorax:
  • Small (<2cm rim): Conservative management, observe.
  • Large (>2cm) or symptomatic: Chest drain insertion.
  • Tension Pneumothorax: Immediate needle decompression (2nd intercostal space, mid-clavicular line) followed by chest drain.
• Pleural Effusion: Treat underlying cause. Diagnostic/therapeutic thoracentesis. Chest drain for large or symptomatic effusions.
• Lung Cancer: Multidisciplinary team (MDT) approach. Options include surgery (for early-stage disease), radiotherapy, chemotherapy, targeted therapy, immunotherapy, and palliative care.

Exam Red Flags