Diagnosis: Community-Acquired Pneumonia (CAP)

Most Likely Causative Organisms (Age 2-5 Years)

"In children between 2 and 5 years of age, most community-acquired pneumonia is caused by respiratory viruses, notably respiratory syncytial virus, human rhinovirus, and human metapneumovirus. Other notable pathogens in this age group include Streptococcus pneumoniae, H. influenzae type b, and nontypeable H. influenzae. Mycoplasma pneumoniae and Chlamydophila pneumoniae are thought to be less common in children <5 years old."

• Tintinalli's Emergency Medicine, p. 853

Clinical Features Explained

Pathophysiology

Workup

• Chest X-ray - lobar/segmental consolidation favors bacterial; bilateral interstitial infiltrates favor viral/atypical
• CBC - leukocytosis with neutrophilia suggests bacterial etiology
• Blood culture - in hospitalized children (yield ~3-7% but useful when positive)
• Nasopharyngeal swab for rapid viral panel (RSV, influenza, rhinovirus, metapneumovirus)
• Pulse oximetry and respiratory rate - key severity markers
• CRP / Procalcitonin - procalcitonin >0.25 ng/mL supports bacterial etiology

Treatment

Physical Examination Findings in Pulmonary Consolidation

Summary Table (from Murray & Nadel's Respiratory Medicine)

Murray & Nadel's Textbook of Respiratory Medicine, Table 18.4

Finding-by-Finding Breakdown

1. Inspection

• Chest wall lag / splinting on the affected side - the patient subconsciously limits expansion of the painful/consolidated side
• Tachypnea - increased respiratory rate is one of the most sensitive early signs
• Use of accessory muscles in severe disease

2. Palpation - Increased Tactile Fremitus

• Ask the patient to say "99" or "one, one, one" and feel chest wall vibrations with the ulnar edge of the hand
• Consolidated (solid) lung transmits low-frequency sound vibrations better than air-filled lung, so vibration is felt more strongly over the affected area
• Contrast: over a pleural effusion, fremitus is decreased (fluid insulates the chest wall from vibration)

"Tactile fremitus increases over an area of consolidation related to pneumonia." - Frameworks for Internal Medicine

3. Percussion - Dullness

• Consolidated lung is solid, not air-filled, so percussion produces a dull (not resonant) note over the affected area
• A very large effusion produces a "stony dull" or flat note
• Dullness to percussion is consistent with both consolidation and pleural effusion - differentiate by fremitus (increased in consolidation, decreased in effusion)

"Dullness to percussion is consistent with consolidation or a pleural effusion." - Goldman-Cecil Medicine

4. Auscultation - Multiple Signs

• Normally, vesicular (soft, rustling) breath sounds are heard over the lung periphery
• In consolidation, large-airway sounds (normally only heard over the trachea/mainstem bronchi) are transmitted through the solid lung to the chest wall - heard as loud, hollow, bronchial sounds with an audible expiratory phase equal to or longer than inspiration

• Late inspiratory crackles (fine crackles/crepitations) over the affected area
• Caused by the explosive reopening of small airways and alveoli that have collapsed due to fluid/exudate
• Heard classically at the end of inspiration

• Ask patient to say "99" - words are transmitted with abnormally increased clarity and volume over consolidated lung
• Normal aerated lung filters and muffles spoken words; solid lung transmits them sharply

• Ask patient to say "eee" - over consolidation, it is heard through the stethoscope as "ayyy"
• The word "egophony" means "goat sound" (Greek: ego = goat) - the bleating, nasal quality is characteristic
• Mechanism: consolidated lung selectively filters lower frequencies, causing the "ee" vowel to shift upward in pitch to sound like "ay"
• Most common when consolidation and pleural fluid coexist; also heard in uncomplicated lobar pneumonia and pulmonary infarction

"When bronchophony is extreme, spoken words assume a nasal or bleating quality (egophony) and the sound 'ee' is heard through the stethoscope as 'ay'." - Fishman's Pulmonary Diseases and Disorders

• Ask patient to whisper a phrase (e.g., "66 whiskeys, please")
• Normal aerated lung acts as a filter - whispered words are garbled and indecipherable
• Over consolidation, whispered words are heard clearly and distinctly
• Pectoriloquy = "chest speaking" (Latin: pectus = chest, loqui = to speak)
• Has the same significance as bronchophony; indicates non-aerated lung (consolidation, tumor, or compressed lung)

"Normal, aerated lung acts as a filter, making these whispered words garbled and undecipherable. If the words are clearly discernible, then pectoriloquy is present and indicative of underlying nonaerated lung." - Frameworks for Internal Medicine

Why These Signs Occur - The Unifying Mechanism

Important Caveat

"None of these findings on physical examination is sufficiently sensitive or specific to avoid the need for imaging for radiographic validation."

Radiology Correlation

• Goldman-Cecil Medicine, Figure 35-1

Differentiating Consolidation from Pleural Effusion on Physical Examination

Head-to-Head Comparison Table

The Pivotal Finding: Tactile Fremitus

"Tactile fremitus is increased over an area of consolidation, whereas it is decreased (often absent) over an effusion. The area of compressed lung just above an effusion is sometimes associated with a thin band of increased tactile fremitus and other signs of consolidation."

• Frameworks for Internal Medicine

"Vocal fremitus and tactile fremitus are increased in lung consolidation but decreased in pleural effusion."

• Textbook of Family Medicine 9e

"Vocal fremitus is increased over regions of lungs where there is increased transmission of sound, for example, consolidation from pneumonia. Conversely, fremitus is decreased in conditions in which sound transmission is impaired, for example, pleural effusion."

• Murray & Nadel's Textbook of Respiratory Medicine

• In consolidation, the lung is solid and directly contiguous with the chest wall - it conducts low-frequency vocal vibrations better than normal
• In pleural effusion, fluid sits between the visceral pleura and the chest wall - it acts as an acoustic insulator, blocking vibrational transmission to the examining hand

The Egophony Trap

"Localized egophony ('e-to-a' changes) indicates consolidation of that segment or lobe of the lung; it is NOT present in pleural effusion except in a small band just above the upper edge of the effusion."

• Textbook of Family Medicine 9e

Mediastinal Shift - An Extra Clue for Large Effusions

"The distinction between pleural effusion and atelectasis can be made on physical examination by determining whether the heart and mediastinal contents shift toward or away from the abnormal side."

• Murray & Nadel's Textbook of Respiratory Medicine

Complete Differential: Three Dull Conditions Side by Side

Practical Memory Aid

• Consolidation = solid lung = everything conducted/amplified (fremitus up, bronchial breathing, egophony, pectoriloquy)
• Pleural effusion = fluid barrier between lung and chest wall = everything blocked/silenced (fremitus down, no breath sounds, no voice signs)

Diagnosis: Bronchiolitis

Causative Organism: Respiratory Syncytial Virus (RSV)

Why This Case = Bronchiolitis

The Organism: Respiratory Syncytial Virus (RSV)

"RSV is the most common infectious agent [in bronchiolitis], although influenza virus, adenovirus, parainfluenza virus, human metapneumovirus, coronavirus, and human bocavirus also cause bronchiolitis."

• Swanson's Family Medicine Review

Other causative organisms (in decreasing order of frequency):

Pathophysiology

"Pathophysiologic features of bronchiolitis include inflammation, edema, and necrosis of the epithelial linings of the small airways. Increased production of mucus and bronchospasm are seen in conjunction with wheeze, cough, accessory muscle use, tachypnea, and rhinorrhoea."

• Swanson's Family Medicine Review

1. RSV infects and destroys bronchiolar epithelium
2. Inflammatory edema + increased mucus secretion narrow the small airways
3. Partial airway obstruction creates air trapping (wheeze on expiration, hyperinflation on CXR)
4. Complete obstruction of some bronchioles causes atelectasis (patchy collapse)
5. Ventilation-perfusion mismatch leads to hypoxemia and, in severe cases, hypercapnia

Clinical Features in Detail

Symptoms

• Prodrome (days 1-3): rhinorrhoea, low-grade fever, mild cough - indistinguishable from a common cold
• Lower tract phase (days 3-5): worsening cough, rapid breathing, wheeze, feeding difficulty
• Peak severity: around day 3-5; total illness duration typically 10-14 days

Signs on Examination

• Tachypnea (RR > 50-60/min in infants) - most sensitive sign of severity
• Subcostal/intercostal retractions - increased work of breathing
• Nasal flaring
• Hyperinflation - barrel-shaped chest; liver pushed down (due to air trapping)
• Widespread fine end-expiratory crackles and wheeze (expiratory > inspiratory)
• Hypoxia (SpO2 < 92% in severe disease)
• Poor feeding / dehydration
• Fever is variable - often low-grade or absent

Chest X-Ray Findings

• Bilateral hyperinflation (flat diaphragms, increased AP diameter, >9 posterior ribs visible)
• Peribronchial cuffing (thickened bronchial walls)
• Patchy atelectasis (often right upper lobe - due to small right upper lobe bronchus easily blocked)
• Bilateral interstitial infiltrates
• Note: CXR is NOT routinely recommended - clinical diagnosis is sufficient in typical cases

Diagnosis

• Clinical diagnosis in most cases - no investigations routinely needed
• Rapid antigen test / RT-PCR nasopharyngeal swab can confirm RSV (useful for cohorting in hospital, not to change management)
• Multiplex respiratory panel (e.g., BioFire) detects RSV, hMPV, parainfluenza, and 14-19 other pathogens simultaneously

Management (Evidence-Based)

High-Risk Groups (Severe/Fatal Disease)

"The fatality rate among hospitalized infected infants is estimated to be 0.5%-1%; however, this rises higher in children receiving cancer chemotherapy, infants with congenital heart disease, and those with severe immunodeficiency."

• Sherris & Ryan's Medical Microbiology

• Premature infants (especially < 32 weeks gestation)
• Congenital heart disease (haemodynamically significant)
• Chronic lung disease (e.g., bronchopulmonary dysplasia)
• Immunodeficiency
• Age < 3 months

Prevention

Recent 2025 ALAT Consensus [PMID: 41714249] and 2025 Australasian Bronchiolitis Guideline [PMID: 40685806] confirm supportive care remains the cornerstone of management.