Pneumomediastinum

Pneumomediastinum — the presence of free air within the mediastinal tissues — is classified as primary/spontaneous (no obvious cause such as trauma or instrumentation) or secondary (trauma, iatrogenic, esophageal perforation). Primary spontaneous pneumomediastinum (SPM) is a benign, self-limited condition predominantly affecting young males (mean age ~23 years, 3:1 male predominance), caused by the Macklin phenomenon: alveolar rupture with air dissecting along bronchovascular sheaths into the mediastinum. [1-3] The critical ED challenge is distinguishing this benign entity from Boerhaave syndrome (esophageal perforation), which requires urgent intervention. [3-4]

• Onset and character of chest pain: Acute retrosternal or pleuritic chest pain is the most common symptom (~71–89%), often radiating to the neck, back, or shoulders [1][5]
• Dyspnea (43–57%), neck pain (32–55%), sore throat, odynophagia (14%), dysphagia, and voice change [1][6-7]
• Precipitating events: Forceful coughing (27–34%), retching/emesis (13–24%), physical exertion (11–21%), Valsalva maneuvers (straining, weightlifting, childbirth), inhaled drug use (marijuana, cocaine, vaping) [1][3][8]
• No identifiable trigger in 21–53% of cases [6][9]
• Important negatives: Absence of trauma, recent instrumentation/endoscopy, mechanical ventilation, foreign body ingestion

• Fever — rare in SPM; raises concern for esophageal perforation or mediastinitis [3]
• Pleural effusion on imaging — 100% sensitivity for esophageal perforation when combined with mediastinal fluid; absence of pleural/mediastinal fluid has a 100% NPV for perforation [4]
• Age >40 — rare in SPM and should raise suspicion for secondary causes [3]
• Respiratory compromise (43% of perforation patients vs. 6% of SPM) [4]
• Dysphagia — significantly more common in perforation [4]
• Hemodynamic instability, signs of tension pneumomediastinum or cardiac tamponade physiology [10]
• Concurrent large pneumothorax (~10% of SPM have concomitant pneumothorax) [11]

• Relevant contributors: Inhaled corticosteroids (asthma management), inhaled recreational drugs (cocaine, marijuana, vaping/e-cigarettes) can precipitate alveolar rupture [3][8]
• Treatment medications:
  • Analgesics: NSAIDs, acetaminophen for chest pain [6]
  • Supplemental O₂ (high-flow/100%): Accelerates nitrogen washout and reabsorption of mediastinal air [6][12]
  • Bronchodilators: If underlying asthma/bronchospasm is the trigger [13]
• Prophylactic antibiotics: Generally not required; no benefit demonstrated in SPM [14]
• Cautions: Avoid positive-pressure ventilation if possible (may worsen air leak); avoid medications that provoke emesis

• NPO consideration: Only if esophageal perforation is being actively ruled out; otherwise, diet as tolerated
• Soft diet may be considered if odynophagia is present
• No specific long-term dietary restrictions for SPM

• Pulmonary: Cough, wheezing, dyspnea, history of asthma or reactive airway disease
• GI: Emesis, retching, dysphagia, odynophagia, hematemesis (suggests Boerhaave)
• ENT: Sore throat, voice change, neck swelling/crepitus
• Cardiac: Palpitations (tachycardia common in 31% of SPM) [3]
• Substance use: Inhaled drugs (cocaine, marijuana, nitrous oxide), vaping
• Recent procedures: Dental extraction, endoscopy, intubation

• Collateral: Witnesses to emesis/retching episodes, substance use history (friends/family may provide more accurate drug use history)
• Family history: Asthma, connective tissue disorders (Marfan, Ehlers-Danlos — associated with spontaneous air leaks), alpha-1 antitrypsin deficiency
• Social context: Occupation (diving, wind instrument players), recreational drug use, recent strenuous exercise or athletic activity

• Asthma/reactive airway disease — most common comorbidity (22–27%); only independent risk factor for recurrence (OR ~7–8) [1][5]
• Smoking/tobacco use (~30%) [1]
• Thin body habitus / young male
• Inhaled drug use (cocaine, marijuana, vaping) — rising incidence [8]
• Forceful coughing (any cause: URI, pertussis, asthma exacerbation)
• Valsalva-provoking activities: Weightlifting, straining, childbirth, spirometry
• Diabetic ketoacidosis (Kussmaul breathing) [12]
• Interstitial lung disease (secondary pneumomediastinum) [15]

• Asthma — most important predisposing condition; associated with recurrence [5]
• Prior pneumomediastinum — recurrence rate ~4.6% [5]
• COPD/emphysema, interstitial lung disease, cystic fibrosis
• Connective tissue disorders
• Prior esophageal or airway surgery
• History of eating disorders (forceful vomiting)

• Subcutaneous emphysema: Palpable crepitus in the neck, face, and chest — most common sign (33–54%); present in two-thirds at presentation [1][11]
• Hamman's sign (Hamman's crunch): Crunching/crackling sound synchronous with the cardiac cycle on auscultation — pathognomonic [7][10]
• Vital signs: Tachycardia in ~31%; fever is rare and should prompt concern for perforation [3]
• Neck: Swelling, voice change, tracheal deviation (if tension physiology)
• Lungs: May be clear; wheezing if underlying asthma; decreased breath sounds if concurrent pneumothorax
• Abdomen: Assess for peritoneal signs (if concern for hollow viscus perforation)

• CBC: Leukocytosis is common (~30%) in SPM and does not reliably distinguish from perforation; however, significantly higher WBC is associated with esophageal perforation [3-4][16]
• CRP: Mild elevation common in SPM (mean ~1.0 mg/dL); markedly elevated CRP suggests secondary cause [20]
• BMP: Rule out DKA if clinically suspected
• Lactate: If hemodynamically unstable
• Troponin: If ACS is on the differential
• Blood cultures: Only if febrile or concern for mediastinitis

• Chest X-ray (PA and lateral): First-line; diagnostic in ~69–90% of cases [9][11][21]
  • continuous diaphragm signthymic sail/spinnaker signNaclerio's V sign[18][22]
• CT chest: More sensitive; detects ~30% of cases missed on CXR; indicated when CXR is equivocal or concern for secondary cause [23]
  • absence of pleural effusion/mediastinal fluid[4]
• Esophagram (water-soluble contrast): Rarely indicated; reserve for high suspicion of esophageal perforation (older age, pleural effusion, emesis history, respiratory compromise) [3][9]
• CT with oral contrast: Alternative to esophagram if perforation is suspected

The following figure demonstrates the spectrum of pneumomediastinum findings on both CXR and CT in pediatric patients:

• Esophagogastroduodenoscopy (EGD): Only if high suspicion for esophageal perforation; performed in ~13% historically but invariably negative in true SPM [1][9]
• Bronchoscopy: Rarely needed; consider if tracheobronchial injury suspected [1]
• Pulmonary function testing: After recovery, to evaluate for undiagnosed asthma (especially if no clear precipitant) [13]
• Methacholine challenge: If exercise-induced bronchoconstriction suspected as underlying etiology [13]

• Indications: Obtain to rule out ACS in patients presenting with acute chest pain
• Expected findings in SPM: Usually normal or sinus tachycardia
• Concerning patterns: ST changes, axis deviation, or low voltage (may suggest tension pneumomediastinum with cardiac compression or concurrent pneumopericardium) [10]

SPM is a benign, self-limited condition with no reported mortality across large case series totaling hundreds of patients. [1][6][9] The key clinical decision point is distinguishing SPM from esophageal perforation (Boerhaave syndrome). A practical risk stratification approach:

• Low risk for perforation: Age <40, known precipitant (cough, asthma, exertion), no emesis history, no pleural effusion, no mediastinal fluid on CT → observation alone is appropriate [3-4]
• Higher risk for perforation: Age >40, history of retching/emesis, pleural effusion, elevated WBC, fever, respiratory compromise, dysphagia → further workup with esophagram or CT with oral contrast [3-4][16]

Recurrence rate is low (~4.6%), with asthma being the only independent risk factor for recurrence. [5]

• Conservative management is the standard of care for SPM: [6][9][14]
  • Rest and activity restriction (avoid Valsalva maneuvers)
  • Analgesics: NSAIDs or acetaminophen
  • Supplemental oxygen (high-flow/100%): Promotes nitrogen washout and accelerates air reabsorption [6][12]
  • Treat underlying trigger: Bronchodilators and inhaled corticosteroids for asthma; antiemetics if vomiting [13]
• Prophylactic antibiotics are NOT routinely indicated [14]
• NPO status: Only if esophageal perforation workup is ongoing
• Surgical intervention: Extremely rare; reserved for tension pneumomediastinum with hemodynamic compromise or confirmed esophageal/airway perforation [25]

• ED discharge is safe for well-appearing patients with confirmed SPM, stable vitals, no hypoxia, no pleural effusion, and no concern for secondary cause [14][26]
  • no significant difference in outcomes[26]
• Admission/observation criteria:
  • Significant dyspnea or hypoxia
  • Hemodynamic instability
  • Concern for esophageal perforation (pending workup)
  • Large concurrent pneumothorax
  • Inability to tolerate oral intake
  • Significant comorbidities or diagnostic uncertainty
• Median length of stay when admitted: ~27 hours (pediatric) to 1.8–2.3 days (adult) [3][9][21]
• Specialist consultation: Thoracic surgery if concern for esophageal/airway perforation or tension physiology; pulmonology for undiagnosed underlying lung disease

• Follow-up: Outpatient visit in 1–2 weeks; repeat CXR only if symptoms persist or worsen [2][21]
• Pulmonary follow-up: If asthma is suspected as the underlying trigger, arrange PFTs and asthma management [5][13]
• Return precautions — instruct patients to return immediately for:
  • Worsening chest pain or new-onset severe pain
  • Increasing shortness of breath or difficulty breathing
  • Fever
  • Difficulty swallowing or inability to tolerate fluids
  • Neck swelling that is worsening
• Expected recovery: Symptoms typically resolve within 1–2 days; radiographic resolution within 1–2 weeks [7][20]
• Counseling: Avoid Valsalva maneuvers, heavy lifting, and strenuous exercise until symptoms resolve; smoking cessation; avoid inhaled recreational drugs; inform asthma patients of small recurrence risk (~5%) [5]

1. A Narrative Review of Primary Spontaneous Pneumomediastinum: A Poorly Understood and Resource-Intensive Problem. — Morgan CT, Maloney JD, Decamp MM, McCarthy DP. Journal of Thoracic Disease. 2021.

2. Recurrent spontaneous pneumomediastinum in a child with tracheomalacia. — Dewulf J, Van Daele S, De Baets F. Pediatric Pulmonology. 2017.

3. One Hundred Cases of Primary Spontaneous Pneumomediastinum: Leukocytosis Is Common, Pleural Effusions and Age Over 40 Are Rare. — Morgan CT, Kanne JP, Lewis EE, et al. Journal of Thoracic Disease. 2023.

4. Diagnostic Utility of Computed Tomography in Patients With Spontaneous Pneumomediastinum Evaluated for Suspected Esophageal Perforation. — Keogan AG, Rybachok A, Patel S, et al. World Journal of Surgery. 2025.

5. Primary Spontaneous Pneumomediastinum: 237 Cases in a Single-Center Experience Over a 10-Year Period and Assessment of Factors Related With Recurrence. — Yu MH, Kim JK, Kim T, Lee HS, Kim DK. PloS One. 2023.

6. Clinical Experience of Spontaneous Pneumomediastinum: Diagnosis and Treatment. — Kim KS, Jeon HW, Moon Y, et al. Journal of Thoracic Disease. 2015.

7. Hamman's Sign and Syndrome: A Reminder of Important Clinical Clues. — Mendes J, Boas NV, Gomes C, Santos SD. Pediatric Pulmonology. 2025.

8. Current Assessment and Management of Spontaneous Pneumomediastinum: Experience in 24 Adult Patients. — Koullias GJ, Korkolis DP, Wang XJ, Hammond GL. European Journal of Cardio-Thoracic Surgery : Official Journal of the European Association for Cardio-Thoracic Surgery. 2004.

9. Spontaneous Pneumomediastinum: An Extensive Workup Is Not Required. — Bakhos CT, Pupovac SS, Ata A, Fantauzzi JP, Fabian T. Journal of the American College of Surgeons. 2014.

10. Pneumomediastinum. — Kouritas VK, Papagiannopoulos K, Lazaridis G, et al. Journal of Thoracic Disease. 2015.

11. ACR Appropriateness Criteria® Chest Pain-Child. — Expert Panel on Pediatric Imaging, Dorfman SR, Chan SS, et al. Journal of the American College of Radiology : JACR. 2026.

12. Spontaneous Pneumomediastinum With Subcutaneous Emphysema in a Young Healthy Female, a Case Report. — Molla YD, Abegaz SH, Desita ZT. Heliyon. 2023.

13. Spontaneous Pneumomediastinum Secondary to Undiagnosed Asthma In Military Adult. — Klamfoth J, Koroscil M. Military Medicine. 2024.

14. Management of Spontaneous Pneumomediastinum: Are Hospitalization and Prophylactic Antibiotics Needed?. — Ebina M, Inoue A, Takaba A, Ariyoshi K. The American Journal of Emergency Medicine. 2017.

15. Image Findings and Background Characteristics of Extrapleural Air Collection: A Pneumothorax Mimicker. — Nishinaka H, Oi M, Hiroi T, et al. Journal of Computer Assisted Tomography. 2025.

16. Clinical Significance of Spontaneous Pneumomediastinum. — Potz BA, Chao LH, Ng TT, Okereke IC. The Annals of Thoracic Surgery. 2017.

17. Spontaneous Pneumomediastinum: A Comparative Study and Review of the Literature. — Caceres M, Ali SZ, Braud R, Weiman D, Garrett HE. The Annals of Thoracic Surgery. 2008.

18. Pneumomediastinum: Old Signs and New Signs. — Bejvan SM, Godwin JD. AJR. American Journal of Roentgenology. 1996.

19. Computed Tomographic Findings and Mortality in Patients With Pneumomediastinum From Blunt Trauma. — Lee WS, Chong VE, Victorino GP. JAMA Surgery. 2015.

20. Management of Spontaneous Pneumomediastinum Based on Clinical Experience of 25 Cases. — Takada K, Matsumoto S, Hiramatsu T, et al. Respiratory Medicine. 2008.

21. Management and Outcomes of Spontaneous Pneumomediastinum in Children. — Noorbakhsh KA, Williams AE, Langham JJW, et al. Pediatric Emergency Care. 2021.

22. Pneumomediastinum Revisited. — Zylak CM, Standen JR, Barnes GR, Zylak CJ. Radiographics : A Review Publication of the Radiological Society of North America, Inc. 2000.

23. Spontaneous Pneumomediastinum in 33 Patients: Yield of Chest Computed Tomography for the Diagnosis of the Mild Type. — Kaneki T, Kubo K, Kawashima A, et al. Respiration; International Review of Thoracic Diseases. 2000.

24. Spontaneous pneumomediastinum: A complication of SARS‐CoV‐2 variant delta infection in children. — Prevost B, Leger PL, Sileo C, et al. Pediatric Pulmonology. 2024.

25. Surgical Drainage of Tension Pneumomediastinum in a Newborn: A Rare Lifesaving Intervention. — Yamamichi T, Ibuka S, Yamashita S, et al. Pediatric Pulmonology. 2025.

26. The Unnecessary Workups and Admissions of Adolescents and Young Adults With Spontaneous Pneumomediastinum. — Wald L, Yergin C, Petroze R, Larson S, Islam S. Scientific Reports. 2024.