✅ Model Answer:
• Air outlining the mediastinum (lucent lines separating mediastinal structures).
• Spinnaker sail sign – thymus lifted upwards and laterally (classic in neonates).
• Continuous diaphragm sign – air under diaphragm extending across midline.
• Ring sign – air around the pulmonary artery.
• No mediastinal shift (unlike tension pneumothorax).
• Diagnosis: Neonatal pneumomediastinum.

✅ Model Answer:
• Spinnaker sail sign: A classic radiographic finding in neonates with pneumomediastinum.
• Mechanism: Air in the mediastinum lifts the thymus gland upwards and laterally, causing it to resemble a spinnaker sail (a triangular sail on a sailboat).
• The thymus is outlined by air, giving it a "sail-like" appearance on both sides of the mediastinum.
• Seen only in neonates (because the thymus is prominent in neonates).
• Resolves as the pneumomediastinum resolves.

✅ Model Answer:
• Pathophysiology: Pneumomediastinum occurs when air escapes from the airways into the mediastinum.
• Macklin effect: The mechanism by which air dissects from the alveoli into the mediastinum.
- Increased alveolar pressure (from crying, coughing, vomiting, positive pressure ventilation).
- Alveolar rupture → air tracks along the bronchovascular sheaths.
- Air dissects into the mediastinum → pneumomediastinum.
- Air can also spread to the neck (subcutaneous emphysema) or into the pleural space (pneumothorax).
• Common causes in neonates: Resuscitation (bag-mask ventilation), vigorous crying, meconium aspiration, respiratory distress syndrome, or post-intubation.

✅ Model Answer:
• Respiratory distress – tachypnoea, grunting, retractions, nasal flaring.
• Subcutaneous crepitus (emphysema) – palpable air in the neck and supraclavicular fossa.
• Hamman sign – a crunching, crackling sound heard on auscultation over the left sternal border (synchronous with the heartbeat). This is pathognomonic of pneumomediastinum.
• Decreased breath sounds – may be present if associated with pneumothorax.
• Muffled heart sounds – due to air in the mediastinum.
• Most infants are asymptomatic or have mild symptoms.
• Severe cases: May cause tamponade-like physiology (rare).

✅ Model Answer:
• Hamman sign: A crunching, crackling, or crepitant sound heard on cardiac auscultation over the left sternal border, synchronous with the heartbeat.
• Mechanism: Air in the mediastinum is compressed during systole, producing the characteristic crunching sound.
• Clinical significance: Hamman sign is pathognomonic for pneumomediastinum.
• It is most prominent when the patient is lying on the left side (left lateral decubitus position).
• It may be mistaken for a pericardial rub, but the pericardial rub is not synchronous with the heartbeat and does not have a "crunching" quality.

✅ Model Answer:
• Neonates:
- Respiratory distress syndrome (surfactant deficiency).
- Meconium aspiration syndrome.
- Assisted ventilation (bag-mask, CPAP, mechanical ventilation).
- Vigorous crying or coughing.
- Pneumonia (staphylococcal, viral).
- Esophageal rupture (Boerhaave syndrome – rare).
• Older children:
- Asthma exacerbation (air trapping).
- Foreign body aspiration.
- Blunt chest trauma.
- Coughing paroxysms (pertussis).
- Vomiting (Mallory-Weiss, Boerhaave).
- Spontaneous (idiopathic).

✅ Model Answer:
• Key radiographic signs:
1. Air outlining the mediastinum – lucent lines separating mediastinal structures (heart, great vessels, trachea).
2. Spinnaker sail sign – thymus lifted upwards and laterally (neonates).
3. Continuous diaphragm sign – air under the diaphragm extending across the midline.
4. Ring sign – air around the pulmonary artery.
5. Subcutaneous emphysema – air in the soft tissues of the neck and chest wall.
6. No mediastinal shift – unlike tension pneumothorax (important differentiator).
• A lateral view may show retrosternal air.

✅ Model Answer:
• Pneumomediastinum:
- Air is centrally located (mediastinum).
- Spinnaker sail sign (neonates).
- Continuous diaphragm sign.
- No mediastinal shift (unless tension).
- Air may extend into the neck (subcutaneous emphysema).
- Hamman sign on auscultation.
• Pneumothorax:
- Air is peripherally located (pleural space).
- Visceral pleural line visible.
- Absence of lung markings beyond the pleural line.
- Lung collapse and mediastinal shift (if tension).
- No Hamman sign.
• CT chest can definitively differentiate if needed.

✅ Model Answer:
• Neonatal pneumomediastinum is usually self-limited and resolves spontaneously.
• Management:
1. Supportive care – most infants require only observation.
2. Supplemental oxygen – to increase FiO2 and promote reabsorption of air.
3. Avoid positive pressure ventilation – if intubated, use the lowest possible pressures.
4. Treat the underlying cause – pneumonia, RDS, asthma.
5. Monitor for complications – pneumothorax, tension pneumomediastinum.
6. Tension pneumomediastinum (rare) – may require needle decompression or chest tube insertion (if associated with pneumothorax).
7. Surgical intervention – rarely needed (for esophageal rupture).

✅ Model Answer:
• Pneumothorax – air from the mediastinum can rupture into the pleural space.
• Subcutaneous emphysema – air dissects into the neck and chest wall (usually benign).
• Tension pneumomediastinum – rare; air under pressure can compress the heart and great vessels → cardiac tamponade physiology (hypotension, muffled heart sounds).
• Pneumopericardium – air in the pericardial sac (rare).
• Esophageal rupture – if the cause is Boerhaave syndrome (vomiting).
• Respiratory distress – if the pneumomediastinum is large.

✅ Model Answer:
• This is a pneumothorax complicating the pneumomediastinum.
• Management:
1. If tension pneumothorax (tracheal deviation, hypotension) → immediate needle decompression (2nd ICS, MCL) then chest tube insertion.
2. If non-tension pneumothorax with symptoms → chest tube insertion (4th-5th ICS, anterior axillary line).
3. If small, asymptomatic pneumothorax → observe with oxygen.
4. Continue treatment for the underlying cause (pneumonia, RDS).
5. Monitor for re-expansion pulmonary edema.

✅ Model Answer:
• This is a spontaneous pneumomediastinum due to asthma exacerbation.
• Mechanism: Air trapping (bronchospasm, mucus plugging) → increased alveolar pressure → Macklin effect (alveolar rupture → air tracks into mediastinum).
• Management: Treat the underlying asthma exacerbation (bronchodilators, corticosteroids).
• The pneumomediastinum usually resolves with treatment of the asthma.
• Avoid excessive positive pressure ventilation (if intubated).
• Monitor for pneumothorax.