Shortness of Breath — Causes, Emergency Signs & Evaluation — Causes, Diagnosis & When to See a Doctor | MyMedicPlus

Shortness of breath (dyspnoea) is the distressing, subjective sensation of difficulty breathing, breathing discomfort, or not receiving sufficient air — one of the most alarming and debilitating symptoms a person can experience. It ranges from mild breathlessness occurring only with vigorous exertion to severe respiratory distress that is present at rest and limits all activity. Dyspnoea is a cardinal symptom of many serious cardiac and pulmonary conditions and should never be dismissed or attributed to anxiety without thorough evaluation to exclude organic causes. Severity is graded using the MRC dyspnoea scale from Grade 1 (breathlessness only with strenuous activity) through to Grade 5 (breathless at rest, confined to house or bed). Dyspnoea results from complex interactions between respiratory mechanics, blood gas abnormalities, cardiac function, and central neural processing — multiple systems may be involved simultaneously. The pattern of dyspnoea — whether acute or chronic, exertional or at rest, positional, nocturnal, or episodic — provides crucial diagnostic information. Dyspnoea in a previously fit individual, or new worsening of previously stable breathlessness, always warrants systematic evaluation regardless of age or apparent fitness level.

Respiratory causes include asthma (episodic wheeze, chest tightness, and breathlessness — often worse at night and with triggers), COPD (progressive breathlessness predominantly in smokers with productive cough), community-acquired pneumonia (breathlessness with fever, productive cough, and pleuritic chest pain), pulmonary embolism (acute breathlessness with or without pleuritic chest pain and haemoptysis — often follows DVT), spontaneous pneumothorax (sudden unilateral breathlessness with chest pain — common in tall young men), pleural effusion (breathlessness with reduced breath sounds at the base), interstitial lung disease and pulmonary fibrosis (progressive exertional breathlessness with fine basal crackles), and upper airway obstruction from foreign body, anaphylaxis, or epiglottitis. Cardiac causes include acute heart failure (breathlessness worsened by lying flat — orthopnoea — with bilateral basal crackles and ankle oedema), acute coronary syndrome (breathlessness with or without chest pain — particularly in women and diabetics where breathlessness may be the dominant feature), cardiac arrhythmias (palpitations and breathlessness together), and cardiac tamponade (breathlessness with muffled heart sounds, hypotension, and elevated venous pressure). Other important causes include anaemia (reduced oxygen-carrying capacity causing exertional breathlessness), anxiety and panic attacks (hyperventilation syndrome), severe obesity (impaired respiratory mechanics), metabolic acidosis in diabetic ketoacidosis, and severe sepsis.

Call emergency services immediately for sudden severe breathlessness at rest in a previously well individual — this is a respiratory or cardiac emergency until proven otherwise. Also call emergency services for breathlessness with chest pain or pressure (possible acute myocardial infarction or aortic dissection), breathlessness with coughing up blood (haemoptysis — possible pulmonary embolism, tumour, or severe pneumonia), breathlessness with cyanosis — blue or grey discolouration of the lips, tongue, or fingertips indicating SpO2 below 85% and severe hypoxaemia, breathlessness with stridor (high-pitched inspiratory noise indicating upper airway obstruction from anaphylaxis, foreign body, or epiglottitis), breathlessness with altered consciousness or confusion (possible severe hypoxaemia, hypercapnia, or haemodynamic instability), or breathlessness in a known asthmatic who is not responding to their reliever inhaler after three or more back-to-back puffs. Additional red flags include breathlessness with one-sided painful swollen leg (possible DVT and pulmonary embolism), breathlessness with facial or throat swelling following a sting or new food or medication (anaphylaxis — also call emergency services), and sudden breathlessness in a patient with known heart disease or significant cardiac history — do not wait to see if it improves.

Oxygen saturation (SpO2) measured by pulse oximetry and respiratory rate are assessed immediately — normal SpO2 is 95-100% in healthy adults at sea level; below 92% requires supplemental oxygen and urgent assessment. Chest X-ray identifies pneumonia (consolidation), pneumothorax (absent lung markings), pleural effusion (opacification with fluid level), pulmonary oedema (bilateral perihilar infiltrates, cardiomegaly), and masses. A 12-lead ECG detects arrhythmias, right heart strain pattern (S1Q3T3 pattern of pulmonary embolism), ST changes of ischaemia, and left ventricular hypertrophy. Full blood count identifies anaemia (low haemoglobin) as a cause. D-dimer blood test screens for thromboembolism — negative result in a low-probability patient excludes DVT and PE. CT pulmonary angiography (CTPA) is the definitive investigation for pulmonary embolism. Brain natriuretic peptide (BNP or NT-proBNP) — elevated in heart failure, proportional to severity. Spirometry measures lung function and distinguishes obstructive (asthma, COPD: reduced FEV1/FVC ratio) from restrictive (fibrosis, obesity: reduced FVC with normal ratio) patterns. Echocardiogram evaluates cardiac structure, systolic and diastolic function, valve disease, and pericardial effusion.

Supplemental oxygen corrects hypoxaemia and provides immediate clinical improvement — target SpO2 is 94-98% for most patients (88-92% for COPD patients at risk of hypercapnia). Inhaled short-acting beta-2 agonists (salbutamol, albuterol) via spacer or nebuliser rapidly bronchodilate airways in asthma and COPD — four to eight puffs via spacer is as effective as nebulisation in most cases. Systemic corticosteroids (prednisolone 40 mg oral or hydrocortisone intravenous) reduce airway inflammation in asthma and COPD exacerbations. Diuretics (furosemide intravenous) are the mainstay of acute heart failure treatment, removing fluid from the lungs to restore respiratory mechanics. Antibiotics treat bacterial pneumonia — choice guided by severity, local guidelines, and sputum culture results. Anticoagulation with low molecular weight heparin or DOAC treats pulmonary embolism; thrombolysis (alteplase) is used for massive PE with haemodynamic compromise. Needle decompression followed by chest drain treats tension pneumothorax. Anxiety-related dyspnoea from hyperventilation syndrome responds to controlled breathing retraining, grounding techniques, and treatment of the underlying anxiety disorder with CBT and medication. Iron deficiency anaemia is treated with oral iron supplementation, resolving exertional breathlessness as haemoglobin normalises.

Do not smoke — tobacco smoking is the leading preventable cause of COPD and lung cancer, dramatically worsens asthma and heart failure, and contributes to pulmonary embolism risk. Smoking cessation at any age reduces respiratory decline. Manage all underlying conditions with consistent, appropriate medical treatment: take preventer inhalers daily as prescribed for asthma, attend cardiology follow-up for heart failure optimisation, and use NIV or CPAP for sleep apnoea. Stay physically active to maintain cardiopulmonary fitness — regular aerobic exercise (walking, swimming, cycling) improves exercise tolerance and quality of life even in moderate COPD and heart failure. Achieve and maintain a healthy body weight, as obesity directly impairs respiratory mechanics by reducing diaphragmatic excursion and functional residual capacity. Vaccinate annually against seasonal influenza and receive pneumococcal vaccination as recommended — respiratory infections are the most common trigger of acute exacerbations of asthma, COPD, and heart failure. Avoid known personal asthma triggers including allergens (dust mites, pet dander, pollen), irritants (strong chemical fumes, cigarette smoke), cold air, and aspirin or NSAIDs if aspirin-exacerbated respiratory disease has been identified.

Call emergency services immediately for sudden severe breathlessness at rest, breathlessness with blue or grey discolouration of the lips or fingernails, breathlessness with chest pain, or breathlessness in a known asthmatic not responding to reliever inhaler. These presentations require immediate emergency assessment. Seek emergency department assessment on the same day for new breathlessness with unilateral leg swelling (possible DVT and pulmonary embolism), breathlessness waking you from sleep (orthopnoea or paroxysmal nocturnal dyspnoea — suggests decompensated heart failure), or breathlessness with palpitations suggesting cardiac arrhythmia. Arrange an urgent appointment within one to two days for any new, unexplained breathlessness even if mild — breathlessness that was not previously present deserves explanation. Breathing difficulty on exertion that is limiting usual activities, or that is progressing over days to weeks, warrants prompt assessment with spirometry, chest X-ray, and ECG. Routine review is appropriate for stable, well-characterised breathlessness from known causes such as mild asthma or COPD, for annual reviews and inhaler technique checks. Never assume breathlessness is 'just anxiety' or 'being unfit' without proper assessment — organic cardiac and pulmonary causes must always be excluded first.