Acute cough

Acute cough is cough lasting under 3 weeks. It is the commonest respiratory symptom reported to doctors. Most cases are self limiting viral respiratory tract infections, but the same symptom can herald pneumonia, asthma, chronic obstructive pulmonary disease exacerbation, heart failure, pulmonary embolism, aspiration, foreign body inhalation or tuberculosis.

Clinical relevance. Acute cough accounts for millions of consultations and inappropriate antibiotic prescriptions. Acute bronchitis is by far the commonest diagnosis (over 90% viral). Community acquired pneumonia is found in about 5% of adults with acute cough and fever. Cough from viral infection can last 3 weeks, with 25% persisting at 4 weeks (post infectious cough).

Classification.

• By duration: acute (under 3 weeks), subacute (3 to 8 weeks), chronic (over 8 weeks).
• By character:
  • Dry (viral, irritant, early asthma, ACE inhibitor, heart failure).
  • Productive (bronchitis, pneumonia, bronchiectasis, chronic obstructive pulmonary disease).
  • Nocturnal (asthma, reflux, heart failure, postnasal drip).
  • Paroxysmal (whooping cough).
  • Barking (croup, laryngitis, tracheitis), brassy (tracheal compression), bovine (vocal cord paralysis).
  • Cough on eating or drinking (aspiration).
• By cause:
  • Infective (viral, bacterial, atypical, tuberculous, fungal).
  • Airway (asthma, chronic obstructive pulmonary disease, bronchiectasis), cardiac (heart failure), vascular (pulmonary embolism).
  • Irritant and inhaled (smoke, dust, gases, foreign body, aspiration).
  • Drug related, neoplastic, allergic, psychogenic.

Mechanism. Cough is a protective reflex triggered by irritant, mechanical, chemical, thermal and inflammatory stimulation of vagal afferent receptors in the airway, with enhanced sensitivity after viral infection.

History.

• Onset and duration, character, sputum (colour, volume, blood), timing (nocturnal, on waking, after meals, after exertion), provoking factors (cold air, exercise, lying flat, laughing, allergens).
• Associated symptoms: fever, rigors, sore throat, runny nose, sneezing, headache, myalgia (viral); breathlessness, wheeze, chest pain (pleuritic), haemoptysis (pneumonia, embolism, tuberculosis, cancer); swelling, orthopnoea (heart failure); heartburn, regurgitation, hoarseness (reflux); weight loss, night sweats (tuberculosis, cancer); whoop and vomiting after cough (pertussis).
• Contacts with illness (influenza, COVID-19, pertussis, tuberculosis), travel, vaccination status, smoking, vaping, occupation and exposure (asbestos, silica, mould, bird and animal), recent aspiration or choking episode (foreign body), recent surgery or immobility.
• Past history: asthma, chronic obstructive pulmonary disease, bronchiectasis, heart disease, immunosuppression, HIV, diabetes, cancer, previous tuberculosis, reflux, cystic fibrosis.
• Drugs: ACE inhibitors (cough in 10% to 15%, any time from first dose to months), amiodarone, nitrofurantoin, methotrexate, beta blockers (bronchospasm), inhaled drugs.
• Pregnancy and allergy history.

Examination.

• Vital signs: temperature, respiratory rate (over 24 is abnormal), heart rate, blood pressure, oxygen saturation (under 94% abnormal), work of breathing, ability to complete sentences, confusion.
• General: hydration, cyanosis, clubbing (suppuration, cancer, fibrosis), lymph nodes, throat (pharyngitis, tonsillar exudate, postnasal drip), nose, sinuses, ears.
• Chest: wheeze, crackles (coarse in infection, fine in oedema or fibrosis), bronchial breathing, dullness (consolidation, effusion), stridor, tracheal position, chest wall tenderness.
• Heart and circulation: murmurs, third heart sound, raised jugular venous pressure, oedema.
• Calves (thrombosis).

Red flags.

• Respiratory rate 30 or more, saturation under 92%, confusion, systolic pressure under 90 mmHg, heart rate over 125, temperature over 39 degrees Celsius or under 35 (severe pneumonia, sepsis).
• Haemoptysis, chest pain with breathlessness (embolism, pneumonia, cancer), stridor, drooling, inability to speak (upper airway obstruction, epiglottitis), sudden onset after choking or in a child (foreign body).
• Weight loss, night sweats, cough over 3 weeks with risk factors (tuberculosis, cancer); smoker over 40 with a new cough or change in cough, hoarseness, clubbing, supraclavicular nodes.
• Immunosuppression (HIV, chemotherapy, steroids, transplant), pregnancy, age over 65 with comorbidity.
• Cough with swelling of the face or lips, wheeze, urticaria after exposure (anaphylaxis).
• Paroxysmal cough with whoop or post tussive vomiting in an infant, or contact with pertussis.
• Fever with new murmur, injecting drug use (right sided endocarditis with septic emboli).

Infective. Common cold and viral upper respiratory tract infection, acute bronchitis, influenza, COVID-19, respiratory syncytial virus infection, adenovirus, community acquired pneumonia (Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Legionella, Chlamydia, Staphylococcus aureus). Pertussis, acute sinusitis and postnasal drip, laryngitis and tracheitis, croup, epiglottitis, tuberculosis, pneumocystis pneumonia, fungal infection, pleurisy, lung abscess.

Airway disease. Asthma (cough variant, exacerbation), exacerbation of chronic obstructive pulmonary disease, bronchiectasis exacerbation, cystic fibrosis exacerbation, allergic rhinitis with postnasal drip, vocal cord dysfunction.

Cardiovascular. Acute left heart failure and pulmonary oedema, pulmonary embolism, myocardial ischaemia, pericarditis, mitral stenosis, atrial fibrillation with fast rate.

Aspiration and inhalation. Foreign body (children and elderly), aspiration pneumonitis (dysphagia, stroke, intoxication), inhaled irritants and smoke, chemical pneumonitis, near drowning, anaphylaxis, e-cigarette related lung injury.

Drugs. ACE inhibitors, amiodarone, beta blockers, methotrexate, nitrofurantoin, inhaled corticosteroid, dry powder inhaler irritation, checkpoint inhibitors.

Others. Lung cancer (new or changed cough), pneumothorax, pleural effusion, interstitial lung disease (early), gastro-oesophageal reflux, tracheal compression, psychogenic and habit cough, smoker's cough.

1. Assess severity first: respiratory rate, saturation, heart rate, blood pressure, temperature, mental state. Use CURB-65 (confusion, urea over 7 mmol/L, respiratory rate 30 or more, systolic pressure under 90 or diastolic 60 or under, age 65 or over) to decide setting in pneumonia.
2. Most patients with a normal examination and normal vital signs need no tests (a clinical diagnosis of viral infection or bronchitis).
3. Chest radiograph (posteroanterior and lateral) for suspected pneumonia (fever over 37.8 degrees Celsius, heart rate over 100, respiratory rate over 24, focal chest signs, or saturation under 94%), haemoptysis, risk factors for cancer, weight loss, heart failure, foreign body and persistent cough.
4. Blood tests when pneumonia is suspected:
   • C reactive protein (over 100 mg/L suggests pneumonia; under 20 mg/L makes it unlikely; point of care testing guides antibiotic use).
   • Full blood count, urea, creatinine, electrolytes, liver function, blood cultures (moderate to severe disease), procalcitonin when available.
5. Microbiology in hospital:
   • Sputum Gram stain and culture, urinary antigens for pneumococcus and Legionella.
   • Nasopharyngeal or throat swab for influenza, COVID-19 and respiratory syncytial virus (polymerase chain reaction).
   • Pertussis polymerase chain reaction or culture (in the first 3 weeks) or serology (after 2 to 4 weeks).
   • HIV test, and tuberculosis tests (sputum smear, culture and nucleic acid amplification) if risk or cough persists.
6. Peak expiratory flow or spirometry with reversibility when asthma or chronic obstructive pulmonary disease is suspected (after the acute illness settles); natriuretic peptide, ECG and echocardiography for heart failure; D-dimer and CT pulmonary angiography for embolism.
7. Arterial blood gas for hypoxia, breathlessness at rest or exhaustion.
8. CT chest for unresolved consolidation, haemoptysis, suspected cancer, bronchiectasis, interstitial disease, foreign body; bronchoscopy for foreign body removal and tissue diagnosis.
9. Laryngoscopy for stridor, hoarseness and suspected epiglottitis.
10. Reassess at 6 weeks with a repeat radiograph if pneumonia in smokers over 50 or with a persistent abnormality.

Limits. Clinical diagnosis of pneumonia is only moderately accurate; radiograph may lag by 24 to 48 hours. Sputum colour does not distinguish viral from bacterial infection. Older adults and immunosuppressed patients may have no fever or tachypnoea. C reactive protein and procalcitonin support but do not replace judgement.

Immediate priorities. Treat airway compromise, hypoxia, shock and sepsis first. Call for help for stridor or severe respiratory distress. Give oxygen to keep saturation 94% to 98% (88% to 92% in chronic obstructive pulmonary disease with hypercapnia risk). Start intravenous antibiotics within 1 hour for severe pneumonia or sepsis.

Self limiting viral illness and acute bronchitis (no antibiotic).

• Explain the expected natural history: cough lasts about 3 weeks (average 18 days), antibiotics do not shorten it and cause harm.
• Symptom relief:
  • Fluids, rest, honey (a teaspoon or two, adults and children over 1 year); steam inhalation does not help; lozenges; simple linctus.
  • Paracetamol 1 g every 6 hours (maximum 4 g, 3 g if frail or under 50 kg) or ibuprofen 400 mg every 8 hours with food (maximum 2.4 g) for fever and aches.
  • Dextromethorphan 10 to 20 mg every 4 hours (maximum 120 mg) or codeine linctus 15 mg three or four times daily for troublesome night cough (limited evidence; avoid in children and opioid caution).
  • Saline nasal irrigation and intranasal ipratropium or an intranasal steroid for postnasal drip.
• Delayed antibiotic prescription only when sputum is purulent with high risk of complication or when the patient is systemically unwell (using the criteria for pneumonia).
• Stop smoking and avoid irritants.

Community acquired pneumonia.

• Low severity (CURB-65 0 to 1; treat at home):
  • Amoxicillin 500 mg to 1 g orally three times daily for 5 days (7 days if severe features).
  • Doxycycline 200 mg on the first day then 100 mg daily, or clarithromycin 500 mg twice daily, when penicillin allergic or atypical pathogens are suspected.
• Moderate (CURB-65 2; admit): amoxicillin 500 mg to 1 g three times daily orally or 1 g intravenously every 8 hours plus clarithromycin 500 mg twice daily (or doxycycline) for 7 to 10 days; switch to oral when improving.
• Severe (CURB-65 3 to 5, or intensive care):
  • Co-amoxiclav 1.2 g intravenously every 8 hours (or ceftriaxone 2 g daily, or piperacillin-tazobactam 4.5 g every 6 hours if risk of Pseudomonas) plus clarithromycin 500 mg intravenously twice daily.
  • Add flucloxacillin 2 g every 6 hours or vancomycin 15 to 20 mg/kg every 8 to 12 hours for suspected Staphylococcus aureus (post influenza).
  • Treat for 7 to 10 days. Legionella needs clarithromycin or levofloxacin 500 mg twice daily for 7 to 14 days.
• Supportive:
  • Oxygen, intravenous fluid, venous thromboembolism prophylaxis (enoxaparin 40 mg daily), analgesia for pleurisy (paracetamol, ibuprofen), early mobilisation.
  • Prednisolone 40 mg daily for 5 days (or dexamethasone 6 mg daily) is used in severe pneumonia and COVID-19 with hypoxia by local policy.
• Aspiration pneumonia: amoxicillin with clavulanic acid 625 mg three times daily orally or 1.2 g three times daily intravenously, or ceftriaxone 2 g daily plus metronidazole 500 mg three times daily; assess swallowing.
• Influenza: oseltamivir 75 mg twice daily for 5 days (within 48 hours of onset, or at any time in severe illness and high risk groups).
• COVID-19: supportive care, oxygen, dexamethasone 6 mg daily for up to 10 days if hypoxic, and antiviral treatment (nirmatrelvir with ritonavir 300 mg with 100 mg twice daily for 5 days, or remdesivir) for high risk patients early.
• Pertussis: azithromycin 500 mg on day 1 then 250 mg daily for 4 days, or clarithromycin 500 mg twice daily for 7 days; isolate for 5 days of treatment; treat contacts; cough lasts up to 3 months.
• Tuberculosis: isoniazid 5 mg/kg to a maximum of 300 mg, rifampicin 10 mg/kg to a maximum of 600 mg, pyrazinamide 25 mg/kg to a maximum of 2 g, ethambutol 15 mg/kg for 2 months, then isoniazid and rifampicin for 4 months.
• Give pyridoxine 10 mg daily with tuberculosis treatment. Notify and screen contacts.

Asthma and chronic obstructive pulmonary disease exacerbation.

• Salbutamol 2.5 to 5 mg nebulised (or 4 to 10 puffs by spacer) every 20 minutes for 3 doses then as needed.
• Ipratropium 500 micrograms nebulised every 4 to 6 hours.
• Prednisolone 40 to 50 mg daily for 5 days (asthma 5 to 7 days).
• Antibiotics for chronic obstructive pulmonary disease when sputum is purulent (amoxicillin 500 mg three times daily, or doxycycline 200 mg then 100 mg daily, or clarithromycin 500 mg twice daily for 5 days).
• Controlled oxygen with a target of 88% to 92% in hypercapnic disease. Non invasive ventilation for acidosis.

Heart failure and pulmonary embolism. Furosemide 40 to 80 mg intravenously, glyceryl trinitrate and non invasive ventilation for pulmonary oedema. Anticoagulation for embolism: 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. Alteplase 100 mg over 2 hours for shock.

Foreign body. Back blows and abdominal thrusts for complete obstruction; urgent rigid bronchoscopy for retained foreign body.

Upper airway cough and allergy. Intranasal fluticasone 2 sprays in each nostril daily, saline irrigation, antihistamine (loratadine 10 mg daily), avoid triggers.

ACE inhibitor cough. Stop the drug and switch to an angiotensin receptor blocker (losartan 50 mg daily); cough resolves in 1 to 4 weeks.

Disposition.

• Home: CURB-65 0 to 1, stable, can take oral drugs, adequate support, with review at 48 hours.
• Admit: CURB-65 2 or more, hypoxia, confusion, hypotension, comorbidity (heart failure, chronic obstructive pulmonary disease, immunosuppression), social concerns, failure of outpatient treatment, or suspected embolism.
• Intensive care: respiratory failure, shock, need for ventilation.

Monitoring. Reassess at 48 hours for deterioration, and at 6 weeks to confirm resolution. Repeat chest radiograph at 6 weeks in smokers, those over 50, and with persisting symptoms or signs. Assess for cancer if there is no resolution. In hospital, check vital signs every 4 to 6 hours, C reactive protein trend and oxygen requirement, and switch to oral therapy after 48 to 72 hours.

Referral and escalation. Respiratory team for severe or non resolving pneumonia, haemoptysis, suspected cancer, bronchiectasis, foreign body and cough over 8 weeks. ENT for stridor and hoarseness. Infectious diseases for atypical and tropical infection. Critical care. Public health notification for tuberculosis, pertussis and influenza outbreaks.

Safety netting. Return urgently for breathlessness at rest, worsening fever, chest pain, coughing blood, confusion, drowsiness, blue lips, noisy breathing, inability to drink, or no improvement within 48 hours of antibiotics. Cough lasting over 3 weeks needs review.

Special groups.

• Children: croup (dexamethasone 0.15 mg/kg orally once), foreign body, bronchiolitis, pertussis, pneumonia (amoxicillin 40 to 90 mg/kg/day in three doses); avoid codeine under 12 years.
• Pregnancy: treat pneumonia promptly (amoxicillin, azithromycin), avoid doxycycline, check influenza vaccination; consider pulmonary embolism.
• Older adults: atypical presentations, aspiration, lower threshold for admission and imaging.

Immunosuppressed and HIV: tuberculosis, pneumocystis (co-trimoxazole 120 mg/kg/day in divided doses for 21 days with prednisolone for hypoxia), fungal and atypical infection. Smokers: cancer and chronic obstructive pulmonary disease. Endemic regions: tuberculosis, pneumonia, malaria with respiratory distress, schistosomiasis, paragonimiasis, melioidosis, histoplasmosis and ascariasis must be considered.