General MedicineTier 1Approach to a presentation

Undifferentiated presentations - shortness of breath

Red flags

Sudden onset with pleuritic chest pain + tachycardia - PE until excluded
Stridor - upper airway obstruction, emergency
Silent chest in known asthma/COPD - impending respiratory failure, not improvement
Hypoxia unresponsive to oxygen - consider shunt (PE, ARDS) rather than V/Q mismatch alone
Accessory muscle use, inability to speak in full sentences, exhaustion - impending respiratory failure

Acute

Cardiac: acute pulmonary oedema/decompensated heart failure, ACS, cardiac tamponade, arrhythmia
Respiratory: PE, pneumothorax, asthma/COPD exacerbation, pneumonia, upper airway obstruction (anaphylaxis, foreign body, epiglottitis)
Metabolic: DKA (Kussmaul breathing - compensatory, not primary dyspnoea), salicylate toxicity, severe anaemia, sepsis
Other: anxiety/panic (diagnosis of exclusion), anaphylaxis

Chronic/progressive

COPD, interstitial lung disease, chronic heart failure, pulmonary hypertension, chronic anaemia, obesity, deconditioning, neuromuscular weakness (diaphragmatic)

Onset (sudden vs gradual), positional (orthopnoea, PND - heart failure), exertional pattern, associated chest pain/palpitations/cough/fever
Risk factors for PE (immobility, malignancy, recent surgery, OCP, prior VTE)
Smoking history, occupational exposure, known cardiac/respiratory disease

Work of breathing, accessory muscle use, ability to speak, cyanosis
Chest auscultation (wheeze, crackles, reduced air entry, absent breath sounds - pneumothorax)
JVP, peripheral oedema (heart failure), calf swelling (DVT/PE), tracheal position

Oxygen saturation, ABG/VBG, FBE, UEC, BNP/NT-proBNP, troponin, D-dimer (if pre-test probability low-moderate for PE)
ECG, CXR - first-line for most undifferentiated dyspnoea
CTPA for suspected PE, echocardiogram for suspected heart failure/tamponade, lung function tests for chronic causes

Oxygen for hypoxia (titrate to target, caution with high-flow in chronic CO2 retainers - target lower saturation, e.g., 88-92%)
Treat the underlying cause: diuretics + vasodilators for pulmonary oedema, bronchodilators/steroids for asthma/COPD exacerbation, anticoagulation +/- thrombolysis for PE by severity, needle decompression/chest drain for tension/large pneumothorax
NIV (CPAP/BiPAP) for acute pulmonary oedema or COPD exacerbation with respiratory acidosis, per response
Anxiety-related hyperventilation - manage only after excluding organic causes

A normal chest X-ray does not exclude PE or early heart failure
"Anxiety" is a diagnosis of exclusion - do not apply it before a basic organic workup, especially with objective hypoxia or tachycardia
Silent chest in an asthmatic is a sign of critical airflow limitation, not improvement
High-flow oxygen in chronic CO2 retainers can precipitate hypercapnic respiratory failure - titrate carefully

"Sudden onset with pleuritic pain gets treated as PE until the imaging says otherwise."
"I titrate oxygen, not just maximise it, especially in known CO2 retainers."

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