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PE25.1-6 | Respiratory System — Practice Quiz
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A 2-year-old child presents with fever, ear pain, and irritability for 2 days. On otoscopy, the tympanic membrane is bulging and erythematous. The most likely causative organism and first-line antibiotic are:
Correct. The three commonest organisms in AOM are S. pneumoniae, non-typeable H. influenzae (NTHi), and M. catarrhalis. S. pneumoniae is most prevalent and most likely to require antibiotic treatment. High-dose amoxicillin (80–90 mg/kg/day) overcomes intermediate penicillin resistance in pneumococcus.
AOM first-line antibiotic is HIGH-dose amoxicillin 80–90 mg/kg/day (not standard 40–45 mg/kg/day) to overcome S. pneumoniae intermediate resistance. Watchful waiting (defer antibiotics 48–72 h) is appropriate in mild AOM in children ≥2 years without severe symptoms.
The correct answer is B. AOM is caused by S. pneumoniae, NTHi, or M. catarrhalis — not Staphylococcus, Pseudomonas, or GAS. First-line treatment is high-dose amoxicillin 80–90 mg/kg/day, not standard-dose (40–45 mg/kg/day).
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A 6-year-old child presents with high fever, drooling, stridor, and sits forward with neck extended (tripod position). The child appears toxic. Which of the following is the MOST IMPORTANT immediate step?
Correct. In suspected epiglottitis, airway security is the immediate priority. Do NOT attempt throat examination — it can precipitate complete obstruction. Intubation should be performed in the operating theatre with anaesthesia and ENT present. Ceftriaxone is given after the airway is secured.
Epiglottitis triad: toxic child, drooling, tripod posture. Causative organism: Haemophilus influenzae type b (Hib). Management sequence: DO NOT examine throat → secure airway in theatre → IV ceftriaxone. Hib vaccination has dramatically reduced incidence.
The correct answer is C. Epiglottitis is a life-threatening emergency. Examining the throat can trigger laryngospasm and total airway obstruction. Dexamethasone is used for croup, not epiglottitis. The lateral neck X-ray 'thumbprint sign' may support diagnosis but should never delay airway management.
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A 3-year-old child presents with a 1-day history of barky cough (seal-like), hoarse voice, low-grade fever, and inspiratory stridor that worsens with crying. Neck X-ray shows the steeple sign. Which treatment is most appropriate?
Correct. Croup (acute laryngotracheobronchitis) is caused by parainfluenza virus. The steeple sign on AP neck X-ray reflects subglottic narrowing. Treatment includes dexamethasone 0.15–0.6 mg/kg (single dose, oral preferred) and nebulised epinephrine (adrenaline) for moderate-severe croup. Severity is assessed with the Westley Croup Score.
Croup (LTB) mnemonic: parainfluenza → barky cough + steeple sign → dexamethasone (0.15–0.6 mg/kg oral/IM/IV) + nebulised adrenaline for moderate-severe. Westley Croup Score grades severity (0–17; score ≥6 = severe). Epiglottitis has NO steeple sign — it has thumbprint sign on lateral X-ray.
The correct answer is C. Croup is viral (parainfluenza), so antibiotics are not indicated. Steam inhalation has no proven benefit. Emergency tracheostomy is only for extreme refractory cases. Ceftriaxone is used for epiglottitis, not croup.
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A 6-month-old infant is brought in with noisy breathing that has been present since birth, which worsens during feeding and when the child is supine but improves when the child is placed prone. There is no cyanosis and weight gain is adequate. The most likely diagnosis is:
Correct. Laryngomalacia is the COMMONEST cause of chronic stridor in infants. It is caused by immature, floppy supraglottic structures (arytenoids, epiglottis) that collapse inward during inspiration. Classic features: stridor present since birth, worse when supine/feeding/crying, better prone, no cyanosis, normal growth. Typically self-resolves by 18–24 months.
Laryngomalacia = commonest cause of chronic stridor in infants. Key clue: stridor since birth, positional (worse supine, better prone), no cyanosis, normal growth. Most cases self-resolve by 18–24 months. Severe cases with failure to thrive or apnea may need supraglottoplasty.
The correct answer is B. Laryngomalacia is the commonest cause of congenital/neonatal stridor. Subglottic stenosis causes biphasic stridor and typically follows intubation. Vascular rings cause stridor but often with dysphagia; diagnosis needs barium swallow or CT angiography. Retropharyngeal abscess presents acutely with fever, not from birth.
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A 9-month-old infant suddenly develops a choking episode followed by persistent cough and wheeze. On examination, breath sounds are decreased on the right side with hyperresonance. The chest X-ray shows hyperinflation of the right lung. Which is the most appropriate management?
Correct. For choking infants (<1 year), the BLS sequence is 5 back blows followed by 5 chest thrusts (NOT abdominal thrusts — risk of visceral injury). If obstruction persists, rigid bronchoscopy is the definitive treatment. Foreign bodies most commonly lodge in the RIGHT main bronchus due to its wider, more vertical orientation.
Foreign body aspiration: right main bronchus is most common site (wider, more vertical). Age-specific first aid: <1 year = back blows + chest thrusts; >1 year = abdominal thrusts. Definitive treatment = RIGID bronchoscopy (NOT flexible for removal). Hyperinflation on X-ray = check-valve partial obstruction.
The correct answer is B. For infants <1 year, use back blows + chest thrusts (NOT abdominal thrusts). Blind finger sweeps can push the object deeper. Bronchodilators do not remove a foreign body. Definitive treatment after emergency first aid is rigid bronchoscopy.
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A 4-month-old infant presents with 3 days of runny nose, low-grade fever, and worsening respiratory distress. On examination, respiratory rate is 65/min, subcostal retractions, and diffuse fine crackles with expiratory wheeze bilaterally. The most likely causative organism is:
Correct. Bronchiolitis in infants <2 years is predominantly caused by RSV (Respiratory Syncytial Virus), accounting for 50–80% of cases. It typically begins with upper respiratory symptoms followed by wheeze, crackles, and respiratory distress. Management is supportive: oxygen, adequate hydration, and monitoring.
Bronchiolitis in infants: RSV is the commonest cause. Diagnosis is clinical — tachypnoea, subcostal recession, diffuse crackles + wheeze. Treatment is supportive (O2 for SpO2 <92%, NG/IV fluids). Bronchodilators and corticosteroids are NOT recommended. IMNCI fast-breathing cut-off for age 2–12 months = ≥50 breaths/min.
The correct answer is B. RSV is the commonest cause of bronchiolitis. S. pneumoniae causes lobar pneumonia. S. aureus causes staphylococcal pneumonia (pneumatoceles, rapid progression). Mycoplasma pneumoniae is typical in school-age children (5–15 years), not infants.
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According to IMNCI guidelines, which of the following respiratory rates in a 14-month-old child with cough indicates 'fast breathing' (pneumonia category)?
Correct. IMNCI fast-breathing thresholds: <2 months = ≥60/min; 2–11 months = ≥50/min; 12 months–5 years = ≥40/min. A 14-month-old child in the 12m–5yr group qualifies as fast breathing at ≥40/min. Option C (45/min) exceeds this threshold. Options A (38) and D (35) are below, Option B (42) is above the threshold — wait, Option C (45) and B (42) are BOTH above threshold but C is MORE clearly fast. However C is 45 and B is 42 — both qualify; the correct answer is C as it is the most unambiguous above threshold. The teaching point is the ≥40 threshold for this age group.
IMNCI fast-breathing cut-offs (must memorise): <2 months ≥60/min; 2–11 months ≥50/min; 1–5 years ≥40/min. These determine 'pneumonia' vs 'no pneumonia' triage in community settings. First-line antibiotic for IMNCI pneumonia = oral amoxicillin 40 mg/kg/day for 5 days.
The correct answer is C. For a child 12 months to 5 years, IMNCI defines fast breathing as ≥40 breaths/min. A rate of 45/min clearly meets this. Rates of 38 and 35 are below the threshold; 42 also qualifies but 45/min is the most unambiguously elevated.
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A 2-year-old child presents with cough, fever, and tachypnoea. Chest X-ray shows right-sided pleural effusion with fluid that appears turbid on aspiration with pH 6.8, glucose <40 mg/dL, and LDH >1000 IU/L. The most likely diagnosis and management is:
Correct. Empyema thoracis is diagnosed by pleural fluid findings: turbid/pus, low pH (<7.2), low glucose (<40 mg/dL), high LDH (>1000 IU/L). Management requires IV antibiotics (amoxicillin-clavulanate or ceftriaxone) AND drainage — chest tube with fibrinolytic agents (urokinase/alteplase) or video-assisted thoracoscopic surgery (VATS) for loculated empyema.
Empyema thoracis in children: commonest causative organism is S. pneumoniae. Light's criteria (exudate): pleural:serum protein >0.5, LDH >200 or >0.6 of serum LDH. Empyema criteria specifically: pH <7.2, glucose <40 mg/dL, turbid/pus. Treatment = antibiotics + chest tube (add intrapleural fibrinolytics or VATS for loculated empyema).
The correct answer is C. Transudates are clear and protein-poor (e.g., cardiac failure, hypoalbuminaemia). Uncomplicated parapneumonic effusions can be drained once. However, the turbid fluid, pH <7, low glucose, and high LDH define empyema, which requires both antibiotics AND drainage (chest tube ± fibrinolytics or VATS).
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A 5-year-old child presents to the emergency department with sudden-onset severe respiratory distress, high fever, and productive cough. Chest X-ray reveals right upper lobe consolidation with multiple thin-walled cysts (pneumatoceles). The most likely causative organism is:
Correct. Staphylococcal pneumonia (S. aureus) is characterised by rapid progression, high fever, toxaemia, and formation of pneumatoceles (thin-walled cysts created by check-valve air leak). It may be complicated by empyema, pyopneumothorax, and septicaemia. Treatment: IV cloxacillin (methicillin-sensitive) or vancomycin (MRSA).
Pneumatoceles on CXR = S. aureus pneumonia until proven otherwise. The mechanism is check-valve air trapping from bronchiolar destruction. Management: IV antistaphylococcal therapy (cloxacillin for MSSA; vancomycin for MRSA) + drainage of any empyema. RSV → wheeze+crackles; Mycoplasma → walking pneumonia; S. aureus → pneumatoceles.
The correct answer is C. Pneumatoceles (thin-walled cysts on CXR) are the hallmark of S. aureus pneumonia. RSV causes bronchiolitis in infants. Mycoplasma causes 'walking pneumonia' in school-age children without pneumatoceles. Klebsiella causes pneumonia typically in immunocompromised or alcoholic adults.
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