High-Yield Respiratory Medicine for Medical Exams

Respiratory medicine combines chronic disease management (asthma, COPD), emergencies (PE, pneumothorax, acute asthma) and data interpretation (spirometry, blood gases, chest X-rays). Exams test each of these heavily. This guide is revision material framed around major guidelines.

Spirometry patterns

• Reversibility (a significant improvement after bronchodilator) suggests asthma.
• Transfer factor (DLCO): reduced in emphysema and interstitial lung disease, raised in pulmonary haemorrhage and polycythaemia; normal in pure chest wall restriction.

Arterial blood gas in four steps

1. pH: acidaemia below 7.35, alkalaemia above 7.45.
2. Primary process: carbon dioxide high with acidaemia means respiratory acidosis; bicarbonate low with acidaemia means metabolic acidosis.
3. Compensation: is the other system moving to correct it?
4. Oxygenation: hypoxaemia with normal CO2 is type 1 respiratory failure; hypoxaemia with high CO2 is type 2.

For metabolic acidosis, calculate the anion gap to separate lactic acidosis, ketoacidosis, renal failure and toxins from bicarbonate loss; see high-yield renal and electrolytes.

Asthma

Diagnosis

Variable symptoms (wheeze, breathlessness, chest tightness, cough), often worse at night or with triggers, plus objective evidence: reversibility on spirometry, raised FeNO, peak flow variability or bronchial challenge testing, depending on the guideline.

Long-term management themes

Recent international and UK guidance has moved away from short-acting beta-agonist (SABA) monotherapy. The common thread:

Before stepping up: check inhaler technique, adherence, triggers and alternative diagnoses.

Acute asthma severity

Management themes: oxygen to target saturations, nebulised salbutamol (back-to-back if severe), ipratropium for severe attacks, oral prednisolone or intravenous hydrocortisone, intravenous magnesium for severe or life-threatening attacks, and early critical care input.

COPD

• Diagnosis: post-bronchodilator FEV1/FVC below 0.7 with compatible symptoms and exposure (usually smoking).
• Non-drug measures with high value: smoking cessation, pulmonary rehabilitation, vaccination (influenza, pneumococcal, and others per national schedule).
• Inhaled therapy: long-acting bronchodilators (LAMA, LABA, or both) are the basis; add an inhaled corticosteroid in patients with frequent exacerbations and raised blood eosinophils or asthmatic features.
• Long-term oxygen: for chronic hypoxaemia meeting criteria, in non-smokers.

Acute exacerbation

Bronchodilators, oral prednisolone, antibiotics if sputum is purulent or signs of infection, controlled oxygen to 88–92% in patients at risk of hypercapnia, and non-invasive ventilation for persistent hypercapnic respiratory acidosis despite treatment.

Trap: high-flow oxygen in a CO2-retaining COPD patient can worsen acidosis.

Pulmonary embolism

• Risk factors: recent surgery, immobility, malignancy, pregnancy and postpartum, oestrogen therapy, previous VTE, thrombophilia.
• Presentation: sudden breathlessness, pleuritic pain, haemoptysis, tachycardia, hypoxia; the ECG most often shows sinus tachycardia.
• Work-up: clinical probability score (such as Wells). If PE is unlikely, D-dimer; if negative, PE is excluded. If likely, CT pulmonary angiography (V/Q scan in renal impairment, contrast allergy or pregnancy in some settings).
• Treatment: anticoagulation (often a direct oral anticoagulant); thrombolysis for massive PE with haemodynamic instability.
• Duration: at least three months; longer for unprovoked events or ongoing risk.

Pneumothorax

Trap: do not wait for a chest X-ray in suspected tension pneumothorax.

Interstitial lung disease

Lung cancer and pleural disease

• Non-small cell (adenocarcinoma most common, often in non-smokers; squamous cell associated with hypercalcaemia from PTH-related peptide).
• Small cell: central, associated with SIADH and ectopic ACTH, Lambert-Eaton syndrome.
• Superior vena cava obstruction: facial swelling, distended neck veins.
• Pancoast tumour: Horner syndrome and shoulder pain.
• Pleural effusion: Light's criteria separate exudate from transudate; mesothelioma links to asbestos.

Other topics that appear often

• Bronchiectasis: chronic productive cough, recurrent infections; high-resolution CT confirms.
• Cystic fibrosis: autosomal recessive; sweat test; Pseudomonas colonisation.
• Obstructive sleep apnoea: daytime sleepiness, snoring, obesity; continuous positive airway pressure.
• Alpha-1 antitrypsin deficiency: emphysema in a young non-smoker, often lower lobes, plus liver disease.

Common exam traps

• Continuing SABA-only treatment in asthma.
• Missing a normal CO2 as a sign of exhaustion in acute asthma.
• Giving uncontrolled oxygen in COPD with hypercapnia.
• Ordering a D-dimer in high-probability PE instead of imaging.
• Waiting for imaging in tension pneumothorax.
• Overlooking drugs (amiodarone, methotrexate, nitrofurantoin) as a cause of fibrosis.

How to revise

Practise reading spirometry and blood gases until you can classify them in seconds, then learn the step ladders. MediFlow Exam Prep includes data-interpretation questions with explanations. Pair this with high-yield infectious diseases for pneumonia and TB.

Summary

• Spirometry: low FEV1/FVC means obstruction.
• ABG: pH, primary process, compensation, oxygenation.
• Asthma: inhaled steroid-based treatment at every step; recognise life-threatening features.
• COPD: bronchodilators, rehabilitation, controlled oxygen.
• PE: probability first, then D-dimer or imaging; tension pneumothorax is a clinical diagnosis.