2.5 Chest Imaging & Airway Radiography
Key Takeaways
- Rib count helps judge inspiratory volume on a neonatal chest radiograph: roughly 8-9 posterior ribs is a common adequate-inflation reference, but rotation, inspiratory timing, disease, and ventilator data determine whether low volume or air trapping is truly present.
- Assess a neonatal ETT tip with the head neutral and the entire airway visible; mid-tracheal placement around T2-T3 or safely above the carina is a common reference, with the needed margin varying by infant size and head position.
- Classic neonatal radiographic patterns include: reticulogranular 'ground-glass' with air bronchograms in RDS; perihilar streaking and fissure fluid in TTN; asymmetric coarse patchy opacities in MAS; and cystic lucencies with coarse fibrosis in BPD.
Last updated: September 2026
2.5 Chest Imaging & Airway Radiography
Radiographic analysis and pulmonary function testing provide essential objective markers for diagnosing cardiopulmonary pathology, verifying invasive device placement, and assessing disease severity in neonatal and pediatric patients.
Systematic Neonatal & Pediatric CXR Interpretation
Systematic evaluation of neonatal and pediatric chest radiographs (CXRs) avoids diagnostic oversight. Follow a structured approach:
- Technical Quality & Rotation: Ensure medial clavicular ends are equidistant from the vertebral spinous processes. Rotation alters mediastinal contours and distorts lung fields.
- Inspiratory Depth (Rib Counting):
- Adequate neonatal inspiration: Roughly 8 to 9 posterior ribs (or about 6 anterior ribs) above the diaphragm is a common reference, not a stand-alone target.
- Lower-volume appearance: Fewer visible ribs may reflect expiratory timing, rotation, small lung volumes, atelectasis, or restrictive disease and can exaggerate markings and cardiac size.
- Larger-volume appearance: More visible ribs plus flattened diaphragms and widened interspaces can support hyperinflation or air trapping. Correlate with mechanics, support, and the full film before changing pressure.
CXR Line & Tube Verification
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Invasive Device Target Anatomical Location Vertebral Level
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Endotracheal Tube Mid-Trachea (between clavicles T2–T3 (Neonates)
and carina) 1–2 cm above carina (Peds)
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UAC (High Line) Thoracic Aorta (above celiac) T6–T9
UAC (Low Line) Lumbar Aorta (below renals) L3–L4
────────────────────────────────────────────────────────────────────────
UVC IVC / Right Atrial Junction T8–T9 (Diaphragm level)
────────────────────────────────────────────────────────────────────────
Nasogastric Tube Stomach body/fundus Below left hemidiaphragm
────────────────────────────────────────────────────────────────────────
Invasive Line and Tube Verification
- Endotracheal Tube (ETT):
- Position the tip mid-trachea, halfway between the inferior clavicular border and the carina.
- Neonatal landmark: Vertebral bodies T2 to T3 (or 1.0 to 1.5 cm above the carina).
- Older child landmark: 1 to 2 cm above the carina.
- Head Flexion / Extension Dynamics ('The Hose Follows the Nose'): Neck flexion drives the ETT deeper (toward or into the right mainstem bronchus); neck extension pulls the ETT cephalad (increasing accidental extubation risk). Document head position during radiography because flexion and extension can change apparent ETT depth; a neutral position improves comparability when clinically feasible.
- Umbilical Venous Catheter (UVC):
- Enters the umbilical vein, traverses the falciform ligament and ductus venosus, and enters the inferior vena cava (IVC).
- Target position: Junction of the IVC and right atrium, corresponding radiographically to T8 to T9 (at the hemidiaphragm level).
- Danger: A low UVC in the portal venous system risks portal vein thrombosis and hepatic hematoma/necrosis. A high UVC deep in the right atrium risks cardiac arrhythmias, atrial perforation, and pericardial tamponade.
Classic Radiographic Patterns in Neonatal Pulmonary Disease
| Neonatal Condition | Classic Radiographic Signature | Primary Underlying Pathophysiology |
|---|---|---|
| Respiratory Distress Syndrome (RDS) | Diffuse, bilateral, uniform reticulogranular ('ground-glass') opacities, prominent air bronchograms, and low lung volumes (bell-shaped thorax). | Alveolar atelectasis and hyaline membrane formation secondary to endogenous surfactant deficiency. |
| Transient Tachypnea of the Newborn (TTN) | Prominent perihilar streaking ('sunburst' pattern), fluid in the interlobar fissures (horizontal fissure), hyperinflation, and mild cardiomegaly. | Delayed clearance of fetal lung liquid via pulmonary lymphatics and microvasculature. |
| Meconium Aspiration Syndrome (MAS) | Patchy, coarse, asymmetric infiltrates with alternating areas of dense atelectasis and marked hyperinflation; flattened diaphragms. | Chemical pneumonitis combined with mechanical ball-valve small airway obstruction. |
| Bronchopulmonary Dysplasia (BPD) | Coarse reticular densities, areas of cystic lucency ('bubbly lung'), hyperinflation alternating with localized atelectasis. | Chronic lung injury, alveolar simplification, and pulmonary parenchymal fibrosis from prolonged mechanical ventilation and oxygen toxicity. |
| Pneumothorax | Hyperlucent hemithorax, absence of peripheral vascular markings, distinct sharp visceral pleural line, contralateral mediastinal shift. | Rupture of overdistended alveoli dissecting into the pleural space; look for 'deep sulcus sign' on supine radiographs. |
| Congenital Diaphragmatic Hernia (CDH) | Multiple gas-filled cystic bowel loops in the left hemithorax, mediastinal shift to the contralateral right hemithorax, and scaphoid abdomen (lack of bowel gas). | Defect in pleuroperitoneal membrane (foramen of Bochdalek) permitting abdominal viscera into thorax, causing severe pulmonary hypoplasia. |
Pediatric Upper Airway Radiographic Emergencies
Upper airway obstruction in young children requires rapid differential diagnosis between viral subglottic swelling and life-threatening supraglottic bacterial infection.
CROUP (Laryngotracheobronchitis) ACUTE EPIGLOTTITIS
[AP Soft-Tissue Neck CXR] [Lateral Soft-Tissue Neck CXR]
Normal Trachea Base of Tongue
│ │ │
┌──┘ └──┐ ▼
'Steeple' --► │ || │ Subglottic ████ 'Thumbprint Sign'
Narrowing └──┐ ┌──┘ Edema (Enlarged Epiglottis)
│ │ │
│ │ Obliterated
Trachea Vallecula
Croup vs. Acute Epiglottitis
- Croup (Laryngotracheobronchitis):
- View: Anteroposterior (AP) soft-tissue neck radiograph.
- Radiographic Sign: Subglottic symmetric tapered mucosal narrowing known as the 'steeple sign' or 'pencil-point sign.'
- Clinical Presentation: Age 6 months to 3 years; gradual onset, low-grade fever, barking seal-like cough, inspiratory stridor.
- Treatment: Mist therapy, oral or intramuscular dexamethasone (0.6 mg/kg), and nebulized racemic epinephrine (2.25% solution, 0.5 mL) for stridor at rest.
- Acute Epiglottitis:
- View: Lateral soft-tissue neck radiograph.
- Radiographic Sign: Severely swollen, rounded epiglottis projecting into the hypopharynx, known as the 'thumbprint sign', with thickening of the aryepiglottic folds and obliteration of the vallecula.
- Clinical Presentation: Age 2 to 7 years (or unvaccinated infants); acute rapid onset, high fever, severe sore throat, drooling, dysphagia, dysphonia, and tripod (orthopneic) positioning.
- CRITICAL PROTOCOL: Never inspect the posterior pharynx with a tongue depressor or agitate the child. Immediate transfer to the operating room for controlled endotracheal intubation by an anesthesiologist and otolaryngologist.
Test Your Knowledge
A portable anteroposterior chest radiograph is performed on an intubated, mechanically ventilated term neonate. The radiograph demonstrates 7 posterior ribs above the hemidiaphragm bilaterally. The endotracheal tube tip is visualized at the level of the T5 vertebra, resting 2 mm above the carina. How should the respiratory therapist evaluate this radiograph and what intervention is indicated?
A
B
C
D
Test Your Knowledge
A 3-year-old child has acute high fever, drooling, muffled voice, stridor, and tripod positioning. A lateral soft-tissue neck radiograph obtained without agitating the child shows obliteration of the vallecula by a swollen rounded structure. Which diagnosis and radiographic interpretation are correct?
A
B
C
D