Chapter 20 · Respiratory Disorders

Pulmonary anatomy · Acute infections (pneumonia, bronchiolitis, croup, pertussis, TB) · Chronic conditions (asthma, CF, bronchopulmonary dysplasia) · Interstitial lung disease · Respiratory failure · Investigations · Management
📌 Core principles: Bronchiolitis (RSV) is most common LRTI in infants <12m; supportive care only. Asthma – stepwise management (SABA, ICS, LTRA, LABA). Croup (laryngotracheobronchitis) – dexamethasone. CF – multidisciplinary care, PERT, inhaled therapies. Pneumonia – antibiotics only if bacterial suspected (S. pneumoniae, H. influenzae). Respiratory failure – BIPAP/CPAP or intubation; PICU care.

📖 Respiratory Disorders – Key Concepts

🫁 Pulmonary anatomy & function
Upper airway (nose to larynx) – humidification, filtration. Lower airway (trachea to alveoli) – gas exchange. Surfactant reduces surface tension. Lung development continues postnatally.
🦠 Acute infections
Bronchiolitis (RSV) – wheeze, crackles, apnoea in infants; supportive care. Croup (laryngotracheobronchitis) – barking cough, stridor; dexamethasone. Pneumonia – fever, tachypnoea, crackles; antibiotics if bacterial (amoxicillin). Pertussis – paroxysmal cough, post-tussive vomiting; macrolides. TB – persistent cough, weight loss, contact history; rifampicin+isoniazid+pyrazinamide.
🌬️ Asthma
Chronic airway inflammation, reversible obstruction. Stepwise: SABA (salbutamol), ICS (budesonide), LTRA (montelukast), LABA (formoterol). Severe: biologics (omalizumab, mepolizumab).
🩺 Cystic fibrosis (CF)
CFTR mutation. Pancreatic insufficiency, recurrent LRTI (P. aeruginosa, S. aureus), bronchiectasis. Management: PERT, fat-soluble vitamins, airway clearance, inhaled dornase alfa, hypertonic saline, CFTR modulators (ivacaftor, elexacaftor/tezacaftor/ivacaftor).
🧪 Interstitial lung disease (ILD)
Rare, diffuse parenchymal disease (neuroendocrine cell hyperplasia, surfactant protein mutations). Hypoxia, crackles, clubbing. HRCT, lung biopsy, management supportive + steroids/hydroxychloroquine.
⚠️ Respiratory failure
Type 1 (hypoxaemic) – PaO2 <60 mmHg; Type 2 (hypercapnic) – PaCO2 >50 mmHg. Causes: pneumonia, asthma, CF, neuromuscular. Support: oxygen, CPAP/BIPAP, mechanical ventilation, ECMO.

🔎 Symptom-based approach: wheeze, stridor, cough, tachypnoea

1️⃣
Infant with coryza, wheeze, crackles, apnoea (winter) – Bronchiolitis (RSV). Supportive: oxygenation, nasal suction, fluids. No steroids, no bronchodilators routinely.
2️⃣
Barking cough, inspiratory stridor, worse at night – Croup (viral laryngotracheobronchitis). Dexamethasone 0.6 mg/kg (oral/IM). Severe: nebulised epinephrine.
3️⃣
Recurrent episodes of wheeze, cough, triggered by exercise/viruses – Asthma. Spirometry (reversible obstruction), FeNO. Stepwise pharmacotherapy.
4️⃣
Chronic productive cough, FTT, steatorrhoea, recurrent LRTI – Cystic fibrosis. Sweat test, CFTR genetics, PERT, airway clearance.
5️⃣
Persistent cough >3 weeks, contact with TB case, weight loss – Pulmonary TB. CXR (hilar lymphadenopathy, infiltrates), interferon-gamma release assay (IGRA), culture. Rifampicin + isoniazid + pyrazinamide + ethambutol.
⚠️ Red flags in respiratory distress: Grunting, nasal flaring, severe recession, apnoea, cyanosis, silent chest (asthma), stridor + drooling (epiglottitis, airway emergency).

📋 Management algorithms: Asthma, CF, Pneumonia, Croup

🌬️
Asthma – stepwise (GINA)
▪️ Step 1: SABA as needed (salbutamol).
▪️ Step 2: low-dose ICS + SABA.
▪️ Step 3: low-dose ICS + LTRA (montelukast) or low-dose ICS + LABA (formoterol).
▪️ Step 4: medium-dose ICS + LABA, refer.
▪️ Step 5: add-on tiotropium, biologics (omalizumab, mepolizumab, dupilumab).
🩺
Cystic fibrosis – comprehensive care
▪️ Pancreatic enzyme replacement (PERT) with meals/snacks.
▪️ Airway clearance (chest physiotherapy, positive expiratory pressure, oscillating devices).
▪️ Inhaled therapies: dornase alfa (Pulmozyme), hypertonic saline, tobramycin (alternating months).
▪️ CFTR modulators: ivacaftor, lumacaftor/ivacaftor, elexacaftor/tezacaftor/ivacaftor (ETI) based on genotype.
▪️ Monitor annually: spirometry, sputum culture, OGTT, vitamin levels.
🦠
Community-acquired pneumonia (CAP) – paediatric
▪️ Mild: oral amoxicillin 50 mg/kg/day for 5 days.
▪️ Moderate-severe: IV ampicillin or ceftriaxone + azithromycin (atypical coverage).
▪️ No improvement in 48h: broaden coverage (consider MRSA, TB).
🩷
Croup (mild-severe)
▪️ Mild: single dose dexamethasone 0.6 mg/kg (oral/IM).
▪️ Moderate-severe: dexamethasone + nebulised epinephrine (L-epinephrine 5 mL 1:1000).
▪️ Observe for 2-4h post epinephrine.

💡 Reflex prompts – Respiratory Disorders

🦠 A 6-month-old in winter with coryza, wheeze, subcostal recession, and feeding difficulty. Most likely pathogen?
Respiratory syncytial virus (RSV) – bronchiolitis. Supportive care.
📉 A 2-year-old with barking cough, stridor, and fever. First-line therapy?
Dexamethasone 0.6 mg/kg (oral or IM) – reduces severity and hospital stay.
🌬️ A 10-year-old with exercise-induced wheeze, normal spirometry. Best initial therapy?
SABA (salbutamol) before exercise or low-dose ICS daily if frequent symptoms.
🩺 A child with CF, chronic P. aeruginosa colonisation. Inhaled antibiotic of choice?
Tobramycin (alternating months) – reduces sputum density and exacerbations.
📊 A 5-year-old with fever, cough, tachypnoea, and subcostal recession. Chest X-ray shows right lower lobe consolidation. Treatment?
Amoxicillin (oral or IV) – Streptococcus pneumoniae most common.
⚠️ A 3-year-old with acute stridor, drooling, tripod position, muffled voice. Likely diagnosis?
Epiglottitis (H. influenzae type b, vaccine preventable). Emergency airway management, do not examine pharynx.
🧪 A 9-year-old with chronic wet cough, digital clubbing, and FTT. Sweat test 85 mmol/L. Diagnosis?
Cystic fibrosis (pancreatic insufficiency) – CFTR mutation analysis.
🩺 A child with asthma and poor control on high-dose ICS + LABA. Next add-on biologic?
Omalizumab (anti-IgE) if allergic; mepolizumab (anti-IL5) for eosinophilic phenotype.
📉 A 4-month-old with pertussis (paroxysmal cough, post-tussive vomiting). Antibiotic?
Azithromycin (macrolide) – reduces transmission but minimal effect on symptoms if late.
🫁 A neonate with respiratory distress, chest X-ray ground-glass opacities, surfactant deficiency. Diagnosis?
Respiratory distress syndrome (RDS) – surfactant therapy, CPAP.