Master Respiratory Medicine
for MRCP Part 1

What the MRCP Part 1 Tests in Respiratory Medicine

MRCP Part 1 Respiratory Medicine tests the ability to diagnose and manage common and important respiratory conditions based on clinical presentation, imaging, and physiology. Candidates must demonstrate knowledge of evidence-based guidelines for asthma, COPD, pneumonia, pulmonary embolism, interstitial lung disease, and lung cancer. Questions often integrate chest X-ray or CT findings with spirometry values, blood gas interpretation, and first-line pharmacotherapy. Key decisions include when to escalate therapy (e.g., biologics in severe asthma), choice of antibiotic for community-acquired vs. hospital-acquired pneumonia, and interpretation of pleural fluid Light's criteria. Understanding of British Thoracic Society (BTS) and NICE guidelines is essential, including thresholds for oxygen therapy, D-dimer interpretation, and lung cancer referral pathways.

High-Yield Concepts

• Asthma Stepwise Management (BTS/SIGN): Step 1: inhaled short-acting beta-agonist (SABA) as required. Step 2: add inhaled corticosteroid (ICS) 200-800 mcg/day beclometasone equivalent. Step 3: add long-acting beta-agonist (LABA); if poor response, consider LAMA or leukotriene receptor antagonist. Step 4: increase ICS to high dose (≥800 mcg/day) plus LABA ± fourth agent. Step 5: oral corticosteroids (prednisolone) and refer for biologic therapy (omalizumab, mepolizumab, benralizumab).
• COPD Diagnosis and GOLD Classification: Diagnosis requires post-bronchodilator FEV1/FVC <0.70. GOLD 1: FEV1 ≥80% predicted; GOLD 2: 50-79%; GOLD 3: 30-49%; GOLD 4: <30%. Group E (high exacerbation risk: ≥2 moderate exacerbations or ≥1 hospitalisation) should receive triple therapy (ICS/LAMA/LABA). NICE recommends LAMA as first-line for breathlessness and exacerbations.
• Community-Acquired Pneumonia (CAP) Severity and Antibiotics: CRB-65: 1 point each for confusion, RR ≥30, BP <90 systolic or ≤60 diastolic, age ≥65. 0: low risk (home, amoxicillin 500 mg TDS); 1-2: moderate (consider admission, co-amoxiclav + clarithromycin); 3-4: severe (urgent admission, IV co-amoxiclav + clarithromycin, or levofloxacin). CURB-65 includes urea >7 mmol/L.
• Pulmonary Embolism (PE) Diagnostic Pathway: Two-level Wells score: PE unlikely (≤4 points) → D-dimer (age-adjusted: age × 0.1 mg/L if >50 years); if negative, no PE. PE likely (>4 points) → CT pulmonary angiogram (CTPA). High clinical suspicion with renal impairment: V/Q scan. First-line anticoagulation: apixaban or rivaroxaban; alternative: LMWH then warfarin.
• Pleural Effusion: Light's Criteria: Exudate if any of: pleural fluid protein/serum protein >0.5; pleural fluid LDH/serum LDH >0.6; pleural fluid LDH >2/3 upper limit of normal serum LDH. Common causes: parapneumonic (exudate, neutrophils), TB (lymphocytes, ADA >40 U/L), malignancy (cytology, pleural biopsy).
• Interstitial Lung Disease (ILD) Patterns: Usual interstitial pneumonia (UIP): honeycombing, traction bronchiectasis, subpleural basal predominance → idiopathic pulmonary fibrosis (IPF). Nonspecific interstitial pneumonia (NSIP): ground-glass opacities, lower zone predominance, often drug-induced or connective tissue disease. Hypersensitivity pneumonitis: centrilobular nodules, mosaic attenuation, exposure history. Treatment: antifibrotics (pirfenidone, nintedanib) for IPF.
• Lung Cancer: NICE Referral and Staging: Urgent chest X-ray (within 2 weeks) if: haemoptysis, unexplained cough >3 weeks, or unexplained weight loss. CT thorax with contrast then PET-CT for staging. Histology: non-small cell (adenocarcinoma, squamous, large cell) vs. small cell. EGFR mutation testing in adenocarcinoma; ALK, ROS1, PD-L1. First-line: surgery (stage I-II), chemoradiotherapy (stage III), targeted therapy/immunotherapy (stage IV).
• Acute Respiratory Distress Syndrome (ARDS) and Oxygen Therapy: Berlin definition: acute onset, bilateral opacities on CXR not fully explained by effusion/collapse, PaO2/FiO2 ≤300 mmHg on PEEP/CPAP ≥5 cmH2O, no evidence of cardiogenic oedema. Management: lung-protective ventilation (tidal volume 6 mL/kg ideal body weight, plateau pressure ≤30 cmH2O), conservative fluid strategy. BTS guidelines for oxygen: target SpO2 94-98% (88-92% in at-risk of hypercapnia).

Common Traps in Respiratory Medicine Questions

• Confusing asthma and COPD spirometry: asthma shows reversibility, COPD shows fixed obstruction with FEV1/FVC <0.70 post-bronchodilator.
• Using D-dimer alone in elderly without age adjustment (age × 0.1 mg/L) leads to false positives and unnecessary CTPA.
• Forgetting that pleural fluid LDH >2/3 upper limit of normal is a Light's criterion even if protein ratio is <0.5.
• Assuming all pulmonary nodules are malignant: solitary nodule <8 mm in low-risk patient may be followed with CT; PET-CT has limited sensitivity for nodules <8 mm.
• Using antibiotics alone for hospital-acquired pneumonia without considering MRSA or Pseudomonas risk (prior IV antibiotics, hospitalisation >5 days, immunocompromise).
• Misinterpreting type 2 respiratory failure: PaCO2 >6.0 kPa with hypoxaemia; in COPD, target SpO2 88-92% to avoid worsening hypercapnia.

How to Revise Respiratory Medicine for the MRCP Part 1

Prioritise BTS and NICE guidelines for asthma, COPD, CAP, PE, and lung cancer. Focus on interpretation of spirometry, blood gases, and pleural fluid results. Questions frequently present a clinical scenario with a chest X-ray or CT finding and ask for the next diagnostic step or first-line treatment. Practise applying CURB-65, Wells score, and Light's criteria to vignettes. Be comfortable with drug names and doses (e.g., amoxicillin, co-amoxiclav, clarithromycin, apixaban). Review oxygen therapy targets and ARDS definitions. Also, know key interstitial lung disease patterns and when to suspect IPF. Expect integrative questions linking respiratory disease with systemic conditions (e.g., connective tissue disease, renal failure).

Practise it: MedLumen has 50 Respiratory Medicine questions for the MRCP Part 1, each with a full explanation and references.