Acute Bronchitis: Separating It From Pneumonia and Withholding Antibiotics Safely

Introduction

Acute bronchitis is a self-limiting inflammation of the trachea and large bronchi, almost always viral, presenting as an acute cough with or without sputum in a patient who is otherwise systemically well. It is one of the commonest reasons for a primary care consultation in the UK and, along with sore throat and otitis media, one of the largest single drivers of unnecessary antibiotic prescribing.¹

Two clinical tasks define the consultation, and the whole article is really about them:

1. Excluding pneumonia and the other serious causes of an acute cough - because acute bronchitis is a diagnosis of exclusion made in a well patient with a clear chest
2. Withholding antibiotics safely and convincingly - which requires not just the decision but the consultation skills to explain it, since the evidence is unambiguous that antibiotics shorten the illness by well under a day at the cost of side effects and resistance

Aetiology

Over 90% of cases are viral. The virus damages the bronchial epithelium, provoking mucosal oedema, mucus hypersecretion and a transient bronchial hyperresponsiveness which explains both the wheeze some patients develop and the cough that lingers for weeks after everything else has settled.

• Viral - rhinovirus (the commonest), influenza A and B, respiratory syncytial virus, coronaviruses including SARS-CoV-2, adenovirus, parainfluenza and human metapneumovirus
• Bacterial - a small minority. Mycoplasma pneumoniae, Chlamydophila pneumoniae and Bordetella pertussis. Streptococcus pneumoniae and Haemophilus influenzae are frequently cultured from sputum but usually represent colonisation rather than the cause.
• Non-infective irritants - tobacco smoke, vaping, air pollution, dusts and chemical fumes, which both cause bronchitis and prolong it

Clinical features

Symptoms

• Cough - the cardinal symptom, initially dry and later productive of clear, yellow or green sputum. It typically lasts around 3 weeks and may persist for up to 8.
• Preceding coryzal illness - sore throat, nasal congestion and rhinorrhoea in the days beforehand
• Retrosternal chest discomfort - a raw or burning sensation, worse with coughing, from tracheal inflammation. This is not pleuritic.
• Wheeze and mild breathlessness - from transient bronchial hyperresponsiveness
• Low-grade fever and malaise - a high fever with rigors should prompt reconsideration
• Hoarseness if the larynx is involved

Examination

The critical finding in acute bronchitis is a normal chest examination, or at most scattered wheeze and coarse crackles that clear on coughing. The patient looks systemically well.

Differential diagnosis

Acute cough has a long differential, and acute bronchitis is the label that remains once the treatable and dangerous causes have been considered.

• Pneumonia - focal signs, systemic upset, consolidation on the radiograph
• Exacerbation of asthma or COPD - a known diagnosis, wheeze, breathlessness, and a fall in peak flow
• Pertussis - paroxysmal coughing, an inspiratory whoop, post-tussive vomiting, and a cough of more than 2 weeks with little else to find
• Influenza and COVID-19 - abrupt onset with high fever, myalgia and headache; anosmia points to COVID-19
• Pulmonary embolism - breathlessness and pleuritic pain with risk factors, and hypoxia out of proportion to the examination
• Heart failure - orthopnoea, paroxysmal nocturnal dyspnoea, bibasal crackles and oedema
• Lung cancer - a cough that persists beyond 3 weeks, haemoptysis, weight loss or hoarseness, particularly in a smoker
• Tuberculosis - a cough over 3 weeks with night sweats, weight loss and relevant exposure or country of origin
• Gastro-oesophageal reflux - a cough worse when supine and after meals
• ACE inhibitor cough - a dry cough beginning weeks to months after starting the drug
• Postnasal drip and upper airway cough syndrome - throat clearing and a sensation of dripping
• Inhaled foreign body - a sudden onset in a child, with unilateral signs

Investigations

Most patients need no investigation at all. Acute bronchitis is a clinical diagnosis, and testing is directed at excluding an alternative rather than confirming it.

• Chest X-ray - only if pneumonia is suspected (focal signs, abnormal observations, marked systemic upset), if the cough has lasted more than 3 weeks, or if there are red flags for malignancy or tuberculosis
• CRP - where the diagnosis is uncertain in primary care and it will change the decision to prescribe (see below)
• Peak flow or spirometry - if the history suggests underlying asthma, particularly in a patient with recurrent episodes
• Pertussis PCR or serology - for a paroxysmal cough lasting more than 2 weeks
• Influenza and SARS-CoV-2 testing - during periods of circulation, where the result affects treatment or infection control
• Sputum culture - not routinely useful, since it usually grows commensal flora

Management

Self-care, which is the treatment

• Explain the expected course - a cough lasting around 3 weeks, sometimes longer, and that this is normal and not a treatment failure. Setting this expectation is the single most effective way to prevent re-consultation.
• Adequate fluids and rest
• Paracetamol or ibuprofen for fever and discomfort
• Honey - the option with the best evidence for symptom relief in acute cough, and suitable for adults and children over 1 year (never under 1 year, because of infant botulism)
• Pelargonium, guaifenesin or dextromethorphan - may be considered in adults and children over 12, though the evidence is weak
• Smoking cessation - smoking both prolongs the illness and predisposes to recurrence
• Safety-net advice - return if breathless, if the fever persists beyond a few days, if the cough lasts more than 3 weeks, if there is haemoptysis, or if symptoms worsen after initially improving

Antibiotics

NICE guidance is explicit that antibiotics should not routinely be offered for acute cough associated with an upper respiratory tract infection or acute bronchitis in an otherwise well person.¹ The benefit is a reduction in cough duration of well under a day, against a meaningful rate of diarrhoea, rash and candidiasis, and a contribution to antimicrobial resistance.

Consider a back-up or immediate antibiotic where the patient is:

• Systemically very unwell
• At higher risk of complications - significant comorbidity such as heart, lung, liver, renal or neuromuscular disease, immunosuppression, cystic fibrosis, or a premature young child
• Over 65 with two, or over 80 with one, of: hospital admission in the past year, type 1 or 2 diabetes, a history of congestive cardiac failure, or current use of oral corticosteroids

Complications

Complications are uncommon in previously healthy adults, and this is the basis for conservative management.

• Post-infectious cough - the commonest sequel, lasting 3 to 8 weeks from persisting bronchial hyperresponsiveness. Reassurance is usually sufficient; an inhaled bronchodilator helps some patients with associated wheeze.
• Secondary bacterial pneumonia - suspect if the patient deteriorates after initially improving, or develops focal signs and high fever
• Exacerbation of underlying asthma or COPD - the commonest reason a patient with bronchitis becomes genuinely unwell
• Bronchospasm and transient airway hyperresponsiveness
• Rib fracture and cough syncope - rare, but recognised after prolonged violent coughing, particularly in older patients with osteoporosis
• Dehydration and poor oral intake in frail patients

Red flags

Prognosis

Acute bronchitis is self-limiting and resolves completely in the great majority of patients. Around half are better within 2 weeks and most within 3, although a post-infectious cough persisting for up to 8 weeks is common enough to be considered normal and is a frequent source of unnecessary re-consultation and repeat antibiotic courses.

Recovery is slower and complications more likely in smokers, in older patients, and in those with underlying airways disease, immunosuppression or significant comorbidity. Recurrent episodes should prompt a search for an underlying diagnosis rather than a further course of antibiotics - undiagnosed asthma is the commonest answer in younger patients and COPD in older ones, and identifying either changes management far more than any antibiotic would.