Acute dyspnoea

Acute dyspnoea is the sudden or rapidly progressive sensation of difficult, laboured or uncomfortable breathing, developing over minutes to days (under 4 weeks, usually under 48 hours). It is a symptom, not a sign. The patient reports it, while observers record respiratory rate, effort and oxygen saturation.

It signals a threat to airway, breathing or circulation until proved otherwise. The first duty is stabilisation, not diagnosis.

Clinical relevance. Acute dyspnoea accounts for up to 5% of emergency attendances. It carries high mortality when due to pulmonary embolism, acute coronary syndrome, acute heart failure, pneumonia, tension pneumothorax, anaphylaxis or exacerbation of asthma and chronic obstructive pulmonary disease. Multiple causes coexist in older patients. Early use of bedside ultrasound, natriuretic peptide and gas analysis changes the diagnosis in many.

Classification.

• By cause group:
  • airway (obstruction, anaphylaxis, aspiration)
  • lung (asthma, chronic obstructive pulmonary disease, pneumonia, pneumothorax, effusion, pulmonary oedema, pulmonary embolism, acute respiratory distress syndrome, interstitial exacerbation)
  • cardiac (acute heart failure, ischaemia, arrhythmia, valve failure, tamponade, myocarditis)
  • metabolic and haematological (acidosis, anaemia, sepsis, thyrotoxicosis, carbon monoxide poisoning)
  • neuromuscular and chest wall (Guillain-Barre syndrome, myasthenic crisis, rib fractures, flail chest)
  • psychogenic (panic, hyperventilation)
• By severity: mild (speaks in sentences), moderate (speaks in phrases), severe (speaks in words, accessory muscles, saturation under 92%), life threatening (exhaustion, silent chest, cyanosis, confusion, bradycardia, hypotension).
• By pattern: sudden onset (pneumothorax, pulmonary embolism, foreign body, arrhythmia, anaphylaxis), hours to days (pneumonia, heart failure, asthma, chronic obstructive pulmonary disease), orthopnoea and paroxysmal nocturnal dyspnoea (heart failure), platypnoea (right to left shunt).

Mechanism. Dyspnoea arises from increased respiratory drive (hypoxia, hypercapnia, acidosis), increased mechanical load (obstruction, stiff lungs or chest wall), and weakness of respiratory muscles. Afferent signals from chemoreceptors, lung receptors and chest wall mismatch with central motor command.

History (obtained in parallel with resuscitation).

• Onset (sudden or gradual), progression, duration, pattern (exertional, at rest, nocturnal, positional), severity (ability to speak, walk), and trend.
• Associated symptoms: chest pain (pleuritic, central), cough and sputum, haemoptysis, wheeze, fever, palpitations, syncope, leg swelling, orthopnoea, paroxysmal nocturnal dyspnoea, throat or lip swelling, rash, abdominal pain, headache, limb weakness, anxiety, paraesthesia around the mouth.
• Triggers: allergen, food or drug exposure, exercise, cold, smoke, recent infection, choking, trauma, high altitude, diving, long flight.
• Past history: asthma, chronic obstructive pulmonary disease, heart failure, coronary disease, valve disease, arrhythmia, thromboembolism, cancer, kidney disease, neuromuscular disease, sleep apnoea, previous intubation.
• Drugs and substances: bronchodilator use and adherence, beta blockers, aspirin and NSAIDs (aspirin exacerbated asthma), ACE inhibitors (angioedema), anticoagulants, amiodarone, chemotherapy, opioids, cocaine, recent new drug.
• Risk for embolism: immobility, surgery, long travel, pregnancy, oestrogen use, previous venous thromboembolism, cancer, thrombophilia.
• Infection risk: fever, sick contacts, HIV, immunosuppression, recent hospitalisation.

Examination (rapid and focused).

• Airway: voice, stridor, drooling, lip and tongue swelling.
• Breathing: respiratory rate (over 30 severe), pattern, accessory muscle use, tracheal tug, retraction, ability to complete sentences, saturation (and on oxygen), cyanosis, paradoxical movement; chest wall expansion, percussion, auscultation (wheeze, silent chest, crackles, bronchial breathing, pleural rub, absent breath sounds, hyperresonance), tracheal deviation.
• Circulation: pulse (rate, rhythm), blood pressure (and pulsus paradoxus), capillary refill, jugular venous pressure, heart sounds (third sound, murmur, muffled), peripheral oedema, calf swelling, cool peripheries.
• Disability: Glasgow Coma Scale, confusion, drowsiness (hypercapnia), flapping tremor, power, reflexes.
• Exposure: temperature, rash, urticaria, angioedema, signs of trauma, sepsis, track marks.
• Bedside: glucose, ECG, blood gas.

Red flags.

• Stridor, drooling, inability to speak, tripod posture (upper airway obstruction).
• Silent chest, exhaustion, confusion, cyanosis, bradycardia (near fatal asthma or hypercapnic failure).
• Saturation under 90% on air, respiratory rate over 30 or under 8, heart rate over 130 or under 40, systolic blood pressure under 90 mmHg.
• Unilateral absent breath sounds with hypotension and tracheal deviation (tension pneumothorax).
• Pleuritic pain, haemoptysis, leg swelling, tachycardia with clear lungs (pulmonary embolism).
• Chest pain with ECG changes (acute coronary syndrome).
• Rash, wheeze, lip swelling, hypotension after an exposure (anaphylaxis).
• Fever, hypotension, mottling (sepsis).
• Rapidly ascending weakness, bulbar weakness (neuromuscular failure).
• Metabolic acidosis with deep rapid breathing (diabetic ketoacidosis, poisoning).
• Paradoxical chest wall movement after trauma.

Upper airway. Anaphylaxis and angioedema (ACE inhibitor, hereditary), epiglottitis, foreign body, laryngeal oedema, croup, peritonsillar abscess, retropharyngeal abscess, Ludwig angina, vocal cord paralysis, tracheal obstruction, thermal or chemical airway injury.

Lower airway. Acute asthma (including near fatal), chronic obstructive pulmonary disease exacerbation, bronchiolitis, bronchiectasis exacerbation.

Lung and pleura. Pneumonia, aspiration, pneumothorax and tension pneumothorax, large pleural effusion, haemothorax, empyema, pulmonary embolism, acute respiratory distress syndrome, interstitial lung disease exacerbation, pulmonary haemorrhage, inhalational injury, high altitude pulmonary oedema, negative pressure pulmonary oedema, transfusion related lung injury.

Cardiac. Acute left heart failure and cardiogenic pulmonary oedema, acute coronary syndrome, arrhythmia (rapid atrial fibrillation, ventricular tachycardia, bradycardia), acute valve regurgitation (papillary muscle rupture, endocarditis), cardiac tamponade, myocarditis, aortic dissection, hypertensive emergency, cardiomyopathy including Takotsubo, right heart failure.

Metabolic, toxic and haematological. Diabetic ketoacidosis, lactic acidosis, uraemic acidosis, salicylate poisoning, methanol and ethylene glycol poisoning, carbon monoxide poisoning, cyanide, methaemoglobinaemia, sepsis, severe anaemia, thyroid storm, adrenal crisis, fever.

Neuromuscular and chest wall. Guillain-Barre syndrome, myasthenic crisis, motor neurone disease, botulism, spinal cord injury, rib fractures and flail chest, phrenic nerve palsy, severe kyphoscoliosis, abdominal distension or ascites, pregnancy.

Psychogenic and functional. Panic attack, hyperventilation syndrome, vocal cord dysfunction, dysfunctional breathing (diagnosis of exclusion).

1. Resuscitate first (airway, breathing, circulation). Attach monitoring (saturation, ECG, blood pressure), gain intravenous access, and take blood and a gas sample at the same time.
2. Bedside tests within minutes: pulse oximetry, 12 lead ECG, capillary glucose, venous or arterial blood gas with lactate, peak expiratory flow if asthma is suspected, temperature, urine ketones.
3. Chest radiograph (portable if unstable): pneumothorax, consolidation, effusion, oedema, cardiomegaly, hyperinflation, mediastinum, rib fractures, foreign body.
4. Point of care ultrasound: lung (B lines in oedema, absent lung sliding in pneumothorax, consolidation, effusion), heart (left and right ventricular function, effusion, tamponade, valve failure), inferior vena cava, legs (compression ultrasound for deep vein thrombosis).
5. Blood tests:
   • Full blood count, urea, creatinine, electrolytes, liver function, glucose, C reactive protein, procalcitonin.
   • Troponin (high sensitivity, repeat at 1 to 3 hours).
   • Natriuretic peptide. BNP under 100 pg/mL or NT-proBNP under 300 pg/mL makes heart failure unlikely; age adjusted cut offs apply.
   • D-dimer when pulmonary embolism is possible with low or intermediate probability (age adjusted threshold: age x 10 micrograms/L over 50 years).
   • Blood cultures, lactate, coagulation, group and screen, toxicology and salicylate level, carboxyhaemoglobin, methaemoglobin, thyroid function.
6. Pulmonary embolism: use Wells or revised Geneva score with D-dimer. CT pulmonary angiography for intermediate or high probability. V/Q scan if contrast is contraindicated. Echocardiography for right ventricular strain.
7. CT chest for unclear diagnosis, suspected aortic dissection, interstitial disease, pneumonia complications. Coronary angiography for acute coronary syndrome. Echocardiography for heart failure and valve disease.
8. Peak flow, spirometry (once stable), sputum and nasopharyngeal swabs for viruses, urinary antigens, tuberculosis tests where indicated.
9. Neuromuscular failure: forced vital capacity (under 20 mL/kg or falling by 30% or negative inspiratory force under minus 30 cmH2O indicates need for ventilation), neurology review, lumbar puncture, nerve conduction.
10. Diagnosis of exclusion for functional breathlessness after organic causes are reasonably excluded (Nijmegen questionnaire, capnography).

Limits.

• Examination and chest radiograph alone misdiagnose heart failure, pneumonia and chronic obstructive pulmonary disease in over 20% of older patients.
• Pulse oximetry misses hypercapnia. It is falsely normal in carbon monoxide poisoning and methaemoglobinaemia, and falsely low in poor perfusion or nail varnish.
• Natriuretic peptides are raised in many conditions (renal failure, atrial fibrillation, pulmonary embolism, age) and falsely low in obesity.
• D-dimer is non specific.
• Multiple pathologies coexist, so improvement after one treatment does not exclude a second cause.

Immediate priorities (all patients).

• Call for help early for any life threatening feature. Move to a resuscitation area, sit upright unless shocked, and monitor continuously.
• Oxygen for unselected patients: give 15 L/min via non rebreather mask until saturation is known, then titrate to 94% to 98%.
• Oxygen for patients at risk of hypercapnic failure (chronic obstructive pulmonary disease, obesity hypoventilation, neuromuscular disease, chest wall disease): target 88% to 92% with a Venturi mask 24% to 28%, and check gases at 30 to 60 minutes.
• Intravenous access, bloods and gas. Correct hypotension with fluids (500 mL 0.9% sodium chloride) unless heart failure is likely. Treat the apparent cause concurrently.
• Non invasive ventilation (bilevel positive pressure, inspiratory 12 to 20 cmH2O, expiratory 4 to 5 cmH2O) for hypercapnic acidosis (pH 7.25 to 7.35) in chronic obstructive pulmonary disease, and for cardiogenic pulmonary oedema with respiratory distress.
• Continuous positive airway pressure 5 to 10 cmH2O for pulmonary oedema. High flow nasal oxygen (30 to 60 L/min) for hypoxic failure.
• Intubate for airway compromise, exhaustion, refractory hypoxia, worsening acidosis, depressed consciousness or failure of non invasive support. Call anaesthesia and critical care early.

Anaphylaxis and angioedema.

• Adrenaline 0.5 mg (0.5 mL of 1:1,000) intramuscularly into the anterolateral thigh immediately. Repeat every 5 minutes if no response.
• High flow oxygen. 0.9% sodium chloride 500 to 1,000 mL. Chlorphenamine 10 mg intravenously. Hydrocortisone 200 mg intravenously. Nebulised salbutamol 5 mg for wheeze.
• Adrenaline infusion for refractory shock.
• Observe for at least 6 to 12 hours (biphasic reaction). Take mast cell tryptase at 1 to 2 hours. Prescribe an adrenaline auto-injector and refer to allergy.
• ACE inhibitor angioedema: stop the drug permanently and secure the airway early.
• Hereditary angioedema: icatibant 30 mg subcutaneously.

Acute asthma.

• Salbutamol 5 mg nebulised (or 4 to 10 puffs by spacer) every 15 to 20 minutes, with ipratropium 500 micrograms nebulised.
• Prednisolone 40 to 50 mg orally (or hydrocortisone 100 mg intravenously) immediately and daily for 5 days.
• Magnesium sulphate 2 g intravenously over 20 minutes for severe or life threatening attacks.
• Refractory attacks: aminophylline loading 5 mg/kg over 20 minutes (not if on theophylline) then 0.5 mg/kg/hour.
• Intubation with ketamine for near fatal attacks. Oxygen to 94% to 98%.

Chronic obstructive pulmonary disease exacerbation.

• Salbutamol 2.5 to 5 mg and ipratropium 500 micrograms nebulised (driven by air if hypercapnic) every 4 to 6 hours.
• Prednisolone 30 to 40 mg daily for 5 days.
• Antibiotics for purulent sputum: amoxicillin 500 mg three times daily, doxycycline 200 mg then 100 mg daily, or clarithromycin 500 mg twice daily for 5 days. Use co-amoxiclav 625 mg three times daily if severe.
• Controlled oxygen 88% to 92%.
• Non invasive ventilation for pH under 7.35 with PaCO2 over 6.5 kPa.
• Enoxaparin 40 mg daily.

Acute heart failure and pulmonary oedema.

• Sit upright. Give oxygen if hypoxic.
• Furosemide 40 to 80 mg intravenously (double the usual oral dose for chronic users). Repeat in 1 to 2 hours or infuse 5 to 40 mg/hour.
• Glyceryl trinitrate 10 to 200 micrograms/minute infusion (or 400 to 800 micrograms sublingual) if systolic pressure over 110 mmHg.
• Continuous positive airway pressure. Avoid routine morphine.
• Treat the precipitant (arrhythmia, ischaemia, infection, uncontrolled hypertension, valve failure).
• Cardiogenic shock: dobutamine 2.5 to 10 micrograms/kg/minute or noradrenaline 0.05 to 0.5 micrograms/kg/minute.
• Urgent coronary angiography when ischaemic.

Acute coronary syndrome.

• Aspirin 300 mg chewed.
• Ticagrelor 180 mg or clopidogrel 300 to 600 mg.
• Fondaparinux 2.5 mg subcutaneously or unfractionated heparin 70 to 100 units/kg.
• Oxygen only if hypoxic. Glyceryl trinitrate. Morphine 2.5 mg for severe pain.
• Primary percutaneous coronary intervention within 120 minutes for ST elevation.

Pulmonary embolism.

• Haemodynamically stable: rivaroxaban 15 mg twice daily for 21 days then 20 mg daily, or apixaban 10 mg twice daily for 7 days then 5 mg twice daily, or enoxaparin 1 mg/kg twice daily. Start while awaiting imaging in high probability.
• Massive (shock): alteplase 100 mg over 2 hours (10 mg bolus then 90 mg over 2 hours; 50 mg bolus in cardiac arrest).
• Also in massive embolism: unfractionated heparin 80 units/kg then 18 units/kg/hour, and noradrenaline 0.05 to 0.5 micrograms/kg/minute. Consider catheter directed treatment or surgical embolectomy.

Pneumothorax.

• Tension: needle decompression (14 gauge cannula, second intercostal space mid clavicular line or fifth space anterior axillary line), then chest drain.
• Large primary (over 2 cm) or symptomatic: needle aspiration (up to 2.5 L) or small bore drain (12 French).
• Secondary pneumothorax: drain and admit.

Pneumonia and sepsis.

• Antibiotics within 1 hour of recognition of sepsis: co-amoxiclav 1.2 g intravenously every 8 hours with clarithromycin 500 mg intravenously twice daily (or ceftriaxone 2 g daily plus clarithromycin).
• 30 mL/kg crystalloid for hypotension.
• Oseltamivir 75 mg twice daily during influenza season.

Metabolic causes.

• Diabetic ketoacidosis: 0.9% sodium chloride 1 litre in the first hour, then fixed rate insulin 0.1 units/kg/hour, with potassium replacement by serum level.
• Salicylate poisoning: sodium bicarbonate 1.5 mg/kg and urinary alkalinisation, early haemodialysis.
• Carbon monoxide: 100% oxygen (hyperbaric oxygen for severe poisoning, coma or pregnancy).
• Methaemoglobinaemia: methylene blue 1 to 2 mg/kg intravenously.

Neuromuscular failure.

• Monitor vital capacity 4 hourly. Elective intubation when forced vital capacity falls under 15 to 20 mL/kg.
• Guillain-Barre syndrome: intravenous immunoglobulin 0.4 g/kg daily for 5 days.
• Myasthenic crisis: plasma exchange or immunoglobulin.

Panic and hyperventilation. Only after organic causes are excluded: calm reassurance and slow breathing coaching. Do not use paper bag rebreathing.

Disposition.

• Resuscitation room or critical care: respiratory failure, exhaustion, need for non invasive or invasive ventilation, shock, life threatening asthma, tension pneumothorax, massive embolism, anaphylaxis, airway threat.
• Admit: new hypoxia, pulmonary oedema, pneumonia with CURB-65 of 2 or more, embolism, acute coronary syndrome, pneumothorax needing drain, severe asthma or chronic obstructive pulmonary disease exacerbation, new arrhythmia.
• Discharge: only when saturation is 94% or more on air, the cause is clear and treated, vital signs normal, peak flow over 75% of best (asthma), and follow up is arranged.

Monitoring. Continuous saturation, respiratory rate, heart rate, blood pressure and urine output. Repeat gases at 30 to 60 minutes after changing oxygen or ventilation settings. Peak flow before and after treatment. Troponin and natriuretic peptide trends. Early warning score. Reassess every 15 minutes initially.

Referral and escalation. Critical care and anaesthesia for ventilation. Respiratory, cardiology, emergency medicine, interventional radiology, thoracic surgery, ENT for airway, allergy, neurology and toxicology as the cause dictates.

Safety netting. Return urgently for worsening breathlessness, inability to speak in sentences, blue lips, chest pain, fainting, noisy breathing, or swelling of face or tongue. Carry the reliever inhaler and adrenaline auto-injector. Written asthma plan. Stop smoking.

Special groups.

• Children: croup (dexamethasone 0.15 mg/kg), bronchiolitis (oxygen, hydration), asthma, foreign body, epiglottitis. Use weight based dosing. Look for grunting, recession and feeding refusal.
• Pregnancy: pulmonary embolism, peripartum cardiomyopathy, amniotic fluid embolism, asthma, pneumonia and anaemia. Keep saturation over 95%. Do not withhold chest radiograph or CT pulmonary angiography. Left lateral tilt.
• Older adults: atypical presentations, multiple causes, delirium.
• Immunosuppressed: pneumocystis pneumonia (co-trimoxazole 120 mg/kg/day in divided doses with prednisolone 40 mg twice daily for hypoxia), fungal infection and tuberculosis.
• Obese: obesity hypoventilation.
• Altitude and diving: pulmonary oedema (descent, oxygen, nifedipine 30 mg modified release twice daily), decompression illness.
• Endemic regions: severe malaria with respiratory distress, tuberculosis, rheumatic heart disease, sickle cell acute chest syndrome and organophosphate poisoning are leading considerations.