Master CPS - Respiratory
for MSRA

What the MSRA Tests in CPS - Respiratory

The CPS - Respiratory section tests the ability to manage common and emergency respiratory presentations in primary and secondary care, with emphasis on differential diagnosis, appropriate investigation, and evidence-based management. Candidates must demonstrate knowledge of NICE and BTS guidelines for conditions such as asthma, COPD, pneumonia, pulmonary embolism, lung cancer, and tuberculosis. Key decisions include when to refer, when to use scoring systems (e.g., CURB-65, Wells' criteria), and correct interpretation of spirometry, arterial blood gases, and chest imaging. Pharmacology is tested through first-line treatments, step-up therapy, and safety-netting advice. The exam prioritises clinical reasoning over recall of rare diseases.

High-Yield Concepts

• Asthma diagnosis and stepwise management: Diagnose if typical symptoms plus objective evidence of variable airflow obstruction (FEV1/FVC <0.7, reversibility >12% and 200mL, or PEF variability >20%). Step 1: SABA as needed. Step 2: add low-dose ICS (e.g., beclometasone 200-400 mcg/day). Step 3: add LABA (e.g., formoterol); if uncontrolled, increase ICS to medium dose. Step 4: high-dose ICS + LABA, consider add-on tiotropium or montelukast. Step 5: oral corticosteroids (lowest effective dose) and refer for specialist care.
• COPD exacerbation management: First-line: increased SABA via spacer or nebuliser, oral prednisolone 30mg for 5 days, and antibiotics (amoxicillin or doxycycline) if purulent sputum. Assess for type 2 respiratory failure (PaCO2 >6.0 kPa); if present, start NIV (IPAP 10-20 cmH2O, EPAP 4-6). Oxygen target 88-92%. Consider doxapram if NIV contraindicated. Discharge only if stable for 24 hours, with smoking cessation advice and pulmonary rehabilitation.
• Community-acquired pneumonia (CAP) severity and treatment: Use CURB-65: Confusion (AMTS ≤8), Urea >7 mmol/L, Respiratory rate ≥30/min, BP <90/60, age ≥65. Score 0-1: home oral amoxicillin 500mg TDS for 5 days. Score 2: hospital oral doxycycline or amoxicillin + clarithromycin. Score ≥3: severe CAP, IV co-amoxiclav or ceftriaxone + macrolide, consider ITU. If penicillin allergy: levofloxacin or moxifloxacin.
• Pulmonary embolism (PE) diagnostic pathway: Use Wells' criteria: clinical signs of DVT (3), PE as likely as other diagnosis (3), heart rate >100 (1.5), immobilisation/surgery within 4 weeks (1.5), previous DVT/PE (1.5), haemoptysis (1), cancer (1). If PE unlikely (≤4), do D-dimer; if positive, CTPA. If PE likely (>4), proceed directly to CTPA. Anticoagulate with apixaban or rivaroxaban; if severe haemodynamic instability, thrombolysis (alteplase 50mg bolus).
• Lung cancer: red flags and referral: Urgent chest X-ray (within 2 weeks) for: haemoptysis, unexplained cough >3 weeks, unexplained dyspnoea or chest pain, hoarseness, finger clubbing, cervical/supraclavicular lymphadenopathy. Urgent CT thorax (within 2 weeks) if X-ray abnormal or high suspicion. NICE recommends PET-CT for staging if candidate for radical treatment. First-line for NSCLC stage IB-IIIA: surgical resection; if inoperable, chemoradiotherapy. SCLC: platinum-based chemotherapy.
• Tuberculosis: diagnosis and initial treatment: Suspect if persistent cough >3 weeks, night sweats, weight loss, haemoptysis. Sputum for smear microscopy and culture (gold standard). IGRA or Mantoux for latent TB. Treatment: 2 months of rifampicin, isoniazid, pyrazinamide, ethambutol (RIPE), then 4 months of rifampicin and isoniazid. Monitor LFTs; isoniazid may cause peripheral neuropathy (give pyridoxine 10-25mg/day). Notify public health.
• Pleural effusion: diagnostic approach: Ultrasound-guided aspiration. Light's criteria to differentiate transudate (e.g., heart failure) from exudate: protein ratio >0.5, LDH ratio >0.6, LDH >2/3 upper limit normal. For exudates, send for culture, cytology, pH (if pH <7.2, consider empyema requiring drainage). If suspected malignant effusion, send for cytology and consider pleural biopsy. First-line for symptomatic large effusion: therapeutic aspiration or chest drain.
• Acute respiratory distress syndrome (ARDS) management: Berlin definition: acute onset, bilateral opacities on CXR/CT, not fully explained by cardiac failure, PaO2/FiO2 ≤300 (mild 200-300, moderate 100-200, severe <100). Lung-protective ventilation: tidal volume 6 mL/kg ideal body weight, plateau pressure ≤30 cmH2O. Conservative fluid strategy, prone positioning if PaO2/FiO2 <150, consider neuromuscular blockade (cisatracurium) in early severe ARDS. Avoid high FiO2; target SpO2 88-95%.

Common Traps in CPS - Respiratory Questions

• Confusing asthma and COPD: asthma typically has reversibility >12% and 200mL, while COPD shows fixed obstruction (FEV1/FVC <0.7 post-bronchodilator) with minimal reversibility.
• Using CURB-65 in hospitalised patients with suspected aspiration or immunocompromised pneumonia: these require broader-spectrum antibiotics regardless of score.
• Ordering D-dimer in patients with high Wells' score: this is inappropriate; go straight to CTPA to avoid false negatives.
• Forgetting to check LFTs before starting TB therapy: rifampicin and isoniazid are hepatotoxic; baseline and monthly monitoring required.
• Giving high-flow oxygen in COPD without target saturation: this can suppress hypoxic drive and cause hypercapnic respiratory failure; always aim for 88-92%.
• Misinterpreting a normal chest X-ray in suspected PE: a normal CXR does not rule out PE; proceed with validated algorithm.

How to Revise CPS - Respiratory for the MSRA

Focus on guideline-driven decision-making for common presentations: acute dyspnoea, cough, haemoptysis, and pleuritic chest pain. Questions often present a clinical scenario requiring you to choose the next best investigation or management step—not the diagnosis itself. Practise applying scoring systems (CURB-65, Wells', GOLD criteria) to real cases, and memorise first-line antibiotics and step-up asthma regimens. Be comfortable with interpreting spirometry and ABGs (e.g., type 1 vs type 2 failure). Prioritise NICE and BTS guidelines; examiners avoid rare diseases. Review safety-netting advice for discharge (e.g., when to return for asthma exacerbation). Use question banks with clinical vignettes to build speed.

Practise it: MedLumen has 50 CPS - Respiratory questions for the MSRA, each with a full explanation and references.