Synopsis
Assess breathlessness by tempo and physiology, identify the patient who needs immediate respiratory or cardiovascular support, and investigate overlapping pulmonary, cardiac, haematological, metabolic and functional causes without premature closure.
- Start with tempo: seconds to hours suggests obstruction, pulmonary oedema, embolism, pneumothorax, anaphylaxis or metabolic crisis; weeks to months broadens the differential to chronic lung, cardiac, anaemic, neuromuscular and deconditioning causes.
- Measure respiratory rate, work of breathing, SpO2, pulse, blood pressure, temperature and mental state before assuming that a normal-sounding history means physiological stability.
- Treat hypoxaemia to a prescribed target: usually 94-98%, or 88-92% pending blood gases when hypercapnic respiratory failure is a recognised risk; critical hypoxaemia still requires immediate oxygen.
- A normal SpO2 does not exclude pulmonary embolism, metabolic acidosis, anaemia, early asthma, cardiac ischaemia or dysfunctional breathing, and supplemental oxygen can conceal worsening ventilation.
- Use discriminating features: orthopnoea and congestion support heart failure; pleuritic pain and risk factors support embolism; wheeze supports but does not prove airway disease; inspiratory noise localises towards the upper airway.
- First-line chronic assessment usually combines blood count, renal and thyroid profiles, ECG, chest radiograph and spirometry, adding natriuretic peptide, echocardiography, gas transfer, CT or exercise testing to answer specific questions.
- Do not label unexplained breathlessness anxiety until dangerous and common organic causes have been assessed; panic and dysfunctional breathing may coexist with cardiopulmonary disease.
- Trajectory is a test: document baseline exercise tolerance, compare previous observations and investigations, treat the leading cause, and define what lack of improvement will trigger reassessment.
Key red flags
Stridor, inability to complete sentences, marked recession, silent chest, exhaustion, cyanosis, falling respiratory effort or reduced consciousness indicates threatened ventilation or airway patency. Treat immediately rather than sending an unstable patient for routine imaging.
Sudden unexplained breathlessness, pleuritic pain, haemoptysis, syncope, tachycardia or hypoxaemia with recent surgery, immobility, cancer, pregnancy, oestrogen exposure or previous venous thromboembolism raises pulmonary embolism probability; examination and chest radiograph may be non-specific.
Investigation priorities
Establish immediate severity and whether support or monitored care is required.
Management branches
Airway threat, severe work of breathing, shock, altered consciousness, cyanosis or rapidly worsening oxygen requirement.
- Call senior and critical-care help, use ABCDE, attach monitoring, gain access and obtain a bedside glucose; position and support the airway and ventilation before pursuing a detailed differential.
- Give oxygen to the appropriate target and obtain an early blood gas when hypercapnia or severe gas-exchange failure is possible; do not withhold oxygen from critical hypoxaemia because COPD is suspected.
- Treat the leading reversible emergency in parallel—bronchodilation for severe obstruction, adrenaline for anaphylaxis, decompression for tension pneumothorax, sepsis treatment, pulmonary-oedema support or the probability-led embolism pathway.
- Reassess physiology after every intervention and set an explicit escalation plan for non-invasive ventilation, intubation, procedure or transfer; avoid transporting an unstable patient to unmonitored imaging.
New breathlessness without immediate ABCDE compromise and without a secure diagnosis.
- Define onset and discriminators, examine lungs, heart and legs, record oxygenation and obtain ECG, chest radiograph and focused blood tests.