MODULE 1 · GDFM PROGRAMME

Acute Lower Respiratory Infections

Module 1 — M11.2

📅 2026-03-02 🏛 College of Family Physicians Singapore

Learning Objectives

Recognise and immediately manage life-threatening causes of dyspnoea and stridor
Differentiate common acute LRTIs: bronchitis, bronchiolitis, croup, CAP, aspiration pneumonia
Apply CRB-65 to stratify CAP severity and guide admission decisions
Practise antibiotic stewardship — know when NOT to prescribe
Counsel patients and families on vaccination and preventive strategies
Identify red flags requiring emergency referral from primary care

Approach to Dyspnoea — Spot the Emergency First

🚨 Emergency — Act Now

🚨

Dyspnoea in primary care: spectrum from benign to imminently life-threatening
🚨 Red flags: tachycardia, tachypnoea, hypotension, SpO2 <94%, altered mental status, stridor, anaphylaxis
Step 1: ABC assessment — do not delay resuscitation for investigation
Step 2: Targeted history + head-to-toe examination for diagnostic clues
Step 3: Decide — manage in clinic vs. refer to ED via ambulance

Differential Diagnosis of Dyspnoea

Stridor — Partial Upper Airway Obstruction

🚨 Emergency — Act Now

🚨

High-pitched inspiratory sound = turbulent flow through narrowed upper airway
🚨 Acute causes requiring urgent action: foreign body, epiglottitis, anaphylaxis, croup, bacterial tracheitis
Chronic causes: laryngomalacia, subglottic stenosis, vocal cord paralysis, vascular rings
History: age, acuity, fever, drooling, hives, preceding choking episode
Examine: assess tongue, pharynx, rate/depth of breathing — avoid agitating child
Management: airway first — adrenaline/steroids for croup, antibiotics for epiglottitis/tracheitis, surgery for abscess

Croup (Laryngotracheobronchitis) — Assessment & Management

Viral (mostly parainfluenza), peak age 6 months–3 years
Classic triad: barking cough, inspiratory stridor, hoarse voice
Preceded by URTI symptoms (coryza, low-grade fever)
Key: keep child calm — crying worsens obstruction
Mild–moderate: oral prednisolone 1 mg/kg OR dexamethasone 0.15–0.6 mg/kg
🚨 Severe: nebulised adrenaline 4 mL 1:1000 + immediate ambulance transfer

Table summarising the assessment of degree of airway obstruction in croup (mild, moderate, severe, life-threatening) with corresponding clinical features and initial treatment guidelines including nebulised adrenaline, oral prednisolone, and dexamethasone.

Acute Bronchitis — When Not to Use Antibiotics

Definition: acute cough ≤3 weeks, no CXR or clinical evidence of pneumonia
Cause: predominantly viral (RSV, rhinovirus, influenza, coronavirus)
Fever is unusual — if present, suspect influenza or pneumonia instead
Distinguish from pneumonia: vital signs, focal lung signs, CXR
Management: symptomatic — dextromethorphan, guaifenesin, honey (>1 yr)
💎 Antibiotics NOT recommended for otherwise healthy adults — counsel on expected 2–3 week cough

Acute Cough Algorithm

Systematic approach to adult with cough <3 weeks
First: rule out life-threatening diagnoses (PE, tension pneumothorax, anaphylaxis)
Then: assess for LRTI vs URTI vs exacerbation of chronic disease
Red flags: haemoptysis, dyspnoea, constitutional symptoms, risk factors
CXR indicated if: RR >24, HR >100, Temp >38°C, signs of consolidation

Clinical algorithm for the evaluation and management of acute cough, including differentiation between life-threatening and non-life-threatening diagnoses, infectious causes (LRTI/URTI), exacerbations of pre-existing conditions, and red flag symptoms.

Acute Bronchiolitis — RSV in Infants

Most common LRTI in infants <2 years; RSV is the leading cause
Biphasic: 2–4 days URTI → lower respiratory symptoms (wheeze, crepitations, retractions)
🚨 Hospitalise if: SpO2 <90%, severe retractions, poor feeding, young age, high HR
Treatment: supportive only — maintain SpO2 ≥90%, hydration, gentle suctioning
NOT recommended: bronchodilators, epinephrine, steroids, antibiotics, physiotherapy
💎 New: Nirsevimab (Beyfortus®) approved Singapore 2025 — single-dose RSV prophylaxis for all infants

Community-Acquired Pneumonia — Diagnosis

Infection of lung parenchyma outside hospital/long-term care facility
Singapore pathogens: S. pneumoniae (most common), H. influenzae, Moraxella, atypicals
Classic symptoms: fever >38°C, productive cough, dyspnoea
Most valuable examination finding: focal crepitations
💎 CXR is required to reliably diagnose pneumonia — do not rely on clinical features alone
Outpatient labs: limited value; consider procalcitonin, influenza testing if circulating

💎 CRB-65 — Risk Stratification in Primary Care

CRB-65: Confusion, Respiratory rate ≥30, Blood pressure <90 systolic, Age ≥65
Score 0: low risk — suitable for outpatient management
Score 1–2: intermediate risk — consider hospital referral
Score ≥3: high risk — urgent hospital admission
Advantage over CURB-65: no blood test required — ideal for primary care
Always supplement score with clinical judgement (social support, functional status)

CRB-65 scoring table for predicting mortality in community-acquired pneumonia, stratifying patients into low, moderate, and high risk groups with corresponding mortality rates and clinical disposition recommendations.

CAP — Empiric Antibiotic Therapy

No comorbidities: Amoxicillin 1g TDS or Doxycycline 100mg BD
With comorbidities (DM, chronic lung/heart/liver disease): Amoxicillin-clavulanate + macrolide or doxycycline; OR respiratory fluoroquinolone
💎 Macrolide monotherapy no longer recommended — high pneumococcal resistance
Duration: minimum 5 days, guided by clinical stability
Atypical coverage may be required — consider if no response to beta-lactam

Table of standard outpatient antibiotic regimens for community-acquired pneumonia, stratified by presence or absence of comorbidities and risk factors for MRSA or Pseudomonas aeruginosa, with detailed dosing footnotes.

Atypical Pneumonias — Think Zoonotic

Organisms: Legionella, Mycoplasma, Chlamydia pneumoniae (non-zoonotic); Psittacosis, Q fever, Tularemia (zoonotic)
Not visible on Gram stain; resistant to beta-lactam antibiotics
💎 Travel and animal contact history is essential — ask specifically
Legionella clues: diarrhoea, hyponatraemia, confusion, aerosolized water exposure (cooling towers, hotels)
Mycoplasma clues: bullous myringitis, cold agglutinins, erythema multiforme
Treatment: doxycycline, macrolide, or fluoroquinolone (depending on organism)

Aspiration Pneumonia — Who Is at Risk?

Inhalation of colonized oropharyngeal material → polymicrobial pneumonia
Distinct from aspiration pneumonitis (sterile gastric acid → chemical injury)
High-risk patients: stroke, Parkinson's, dementia, elderly, poor dentition, GERD, NG tube
Key pathogens: S. pneumoniae, S. aureus, H. influenzae, Enterobacteriaceae (not just anaerobes)
Radiological clue: infiltrates in gravity-dependent segments (basal lobes if upright; posterior upper lobes if supine)
💎 Anaerobic coverage only for lung abscess or severe periodontal disease — not routine

Aspiration Pneumonia — Imaging & Management

CXR/CT: look for dependent segment infiltrates — basal lobes (upright) or posterior upper lobes (supine)
Cavitary lesions suggest anaerobic infection / lung abscess
Treatment: amoxicillin-clavulanate (oral) or ampicillin-sulbactam (IV); minimum 5 days
🚨 Do NOT give glucocorticoids — antibiotics only
Prevent recurrence: speech therapy, thickened feeds, oral hygiene, semi-recumbent positioning
Advanced dementia: involve family in advance care planning — tube feeding may not improve QoL

Composite figure showing characteristic imaging findings in aspiration pneumonia: (A) PA chest radiograph with cavitary infiltrate in the left lower lobe, (B) bilateral lung infiltrates from recurrent aspiration, (C) CT scan showing right upper lobe posterior cavitary infiltrate, and (D) CT scan with new bilateral posterior gravity-dependent infiltrates post-aspiration.

💎 Key Summary

Key Point

Safety first: vital signs + ABC assessment before any investigation — refer emergencies immediately

Key Point

CRB-65 guides CAP disposition: score 0 = home, ≥1 = consider hospital

Key Point

Antibiotic stewardship: acute bronchitis and bronchiolitis are viral — antibiotics not indicated

Key Point

Vaccines prevent disease: influenza, pneumococcal, COVID-19 boosters for high-risk groups

Key Point

Nirsevimab (2025): single-dose RSV prophylaxis now approved in Singapore for all infants

Key Point

Aspiration pneumonia: think dysphagia risk factors, dependent infiltrates, multidisciplinary prevention

Acute Lower Respiratory Infections

Learning Objectives

Approach to Dyspnoea — Spot the Emergency First

Differential Diagnosis of Dyspnoea

Stridor — Partial Upper Airway Obstruction

Croup (Laryngotracheobronchitis) — Assessment & Management

Acute Bronchitis — When Not to Use Antibiotics

Acute Cough Algorithm

Acute Bronchiolitis — RSV in Infants

Community-Acquired Pneumonia — Diagnosis

💎 CRB-65 — Risk Stratification in Primary Care

CAP — Empiric Antibiotic Therapy

Atypical Pneumonias — Think Zoonotic

Aspiration Pneumonia — Who Is at Risk?

Aspiration Pneumonia — Imaging & Management

💎 Key Summary

References