Extension from neck (dental, pharyngeal) or abdominal source
Pathophysiology
Macklin effect (primary mechanism of SPM)
Sudden increase in alveolar pressure causes alveolar rupture
Air escapes into peribronchial and perivascular adventitia
Air dissects centrally along bronchovascular sheaths toward mediastinum
Air may further extend into neck (subcutaneous emphysema), pericardium, or retroperitoneum
No direct tracheal or esophageal injury present in true SPM
Alveolar rupture triggers
Increased intrathoracic pressure against closed glottis (Valsalva)
Forceful cough generating high transalveolar pressure gradients
Asthma: air trapping and increased alveolar pressure distal to obstructed airways
Inhaled drugs: cocaine, marijuana, vaping — deep inhalation with Valsalva maneuver
Tension physiology (rare)
Continued air leak without decompression pathway
Progressive mediastinal air compresses cardiac structures
Reduces venous return and cardiac output
Analogous to tension pneumothorax but less common
Secondary mechanisms
Boerhaave: transmural esophageal tear from forceful emesis with sudden intraluminal pressure rise
Barotrauma: positive-pressure ventilation causes alveolar over-distension and rupture
Traumatic: direct tracheobronchial laceration or tracheal disruption
Therapeutic Considerations
Nitrogen washout rationale for supplemental oxygen
Mediastinal air is ~80% nitrogen at atmospheric partial pressure
Administration of 100% FiO2 creates nitrogen pressure gradient favouring washout
High-flow oxygen accelerates air reabsorption by 3 to 4 times compared to room air
Mechanism analogous to high-flow oxygen for pneumothorax
Antibiotic stewardship
Prophylactic antibiotics offer no benefit in confirmed SPM
Leukocytosis in SPM (~30%) should not trigger reflexive antibiotic prescribing
Reserve antibiotics for fever, hemodynamic instability, or confirmed secondary cause
Positive-pressure ventilation risk
Avoid NIV, CPAP, and BiPAP when pneumomediastinum is present if clinically possible
If required, use minimum pressures; monitor for clinical deterioration
Intubation decision should weigh respiratory failure risk against barotrauma risk
Recurrence prevention
Asthma: optimise controller therapy and trigger avoidance
Inhaled drug cessation essential
No proven pharmacologic prophylaxis for recurrence in SPM
Inform patients of small recurrence risk (~5%) and recurrence symptoms
Unnecessary workup avoidance
EGD invariably negative in low-risk SPM; should not be routinely performed
Esophagram reserved for high-risk features (age > 40, emesis precipitant, pleural effusion, fever)
CT not always required if CXR diagnostic and clinical picture consistent with low-risk SPM
Patient Discharge Instructions
copy discharge instructions
Diagnosis and expected recovery
Diagnosis: air trapped in the chest cavity around the heart and major airways (pneumomediastinum)
This is most commonly a benign, self-limited condition in young otherwise healthy individuals
Symptoms (chest pain, neck discomfort, voice change) typically improve within 1 to 2 days
The air is gradually reabsorbed by your body; imaging clears within 1 to 2 weeks
Activity restrictions
Rest and avoid strenuous physical activity until follow-up appointment
Avoid heavy lifting, straining, or any activity that increases chest pressure
No competitive sport until cleared by your follow-up physician
Avoid holding your breath (Valsalva maneuvers)
Medications prescribed
Take NSAIDs or acetaminophen for pain as directed
Do not take more than the prescribed dose
Take NSAIDs with food to protect your stomach
If prescribed inhalers or other medications, use exactly as instructed
What to avoid
Smoking: quit smoking; this increases your risk of recurrence
Inhaled recreational drugs: marijuana, cocaine, vaping — these can cause this condition to return
Avoid cough suppressants only if prescribed; treating cough may reduce recurrence
Follow-up
Outpatient physician visit in 1 to 2 weeks
Repeat chest X-ray only if symptoms persist or worsen
If asthma is suspected as your trigger, pulmonary function testing will be arranged
Return to emergency department immediately for
Worsening or severe chest pain
Increasing shortness of breath or difficulty breathing
Fever (temperature > 38.5 C)
Difficulty swallowing or inability to keep fluids down
Worsening neck swelling or puffiness spreading across your face and chest
Feeling faint, dizzy, or your heart is racing
Any new symptom that concerns you
References
Guidelines and key sources
Primary literature and systematic reviews
Morgan CT, Maloney JD, Decamp MM, McCarthy DP. A Narrative Review of Primary Spontaneous Pneumomediastinum: A Poorly Understood and Resource-Intensive Problem. Journal of Thoracic Disease. 2021. PMID 34277063
Morgan CT, Kanne JP, Lewis EE, et al. One Hundred Cases of Primary Spontaneous Pneumomediastinum: Leukocytosis Is Common, Pleural Effusions and Age Over 40 Are Rare. Journal of Thoracic Disease. 2023. PMID 37065555
Keogan AG, Rybachok A, Patel S, et al. Diagnostic Utility of Computed Tomography in Patients With Spontaneous Pneumomediastinum Evaluated for Suspected Esophageal Perforation. World Journal of Surgery. 2025. PMID 41266101
Yu MH, Kim JK, Kim T, Lee HS, Kim DK. Primary Spontaneous Pneumomediastinum: 237 Cases in a Single-Center Experience Over a 10-Year Period and Assessment of Factors Related With Recurrence. PloS One. 2023. PMID 37494372
Kim KS, Jeon HW, Moon Y, et al. Clinical Experience of Spontaneous Pneumomediastinum: Diagnosis and Treatment. Journal of Thoracic Disease. 2015. PMID 26623105
Noorbakhsh KA, Williams AE, Langham JJW, et al. Management and Outcomes of Spontaneous Pneumomediastinum in Children. Pediatric Emergency Care. 2021. PMID 31464878
Bakhos CT, Pupovac SS, Ata A, Fantauzzi JP, Fabian T. Spontaneous Pneumomediastinum: An Extensive Workup Is Not Required. Journal of the American College of Surgeons. 2014. PMID 25053221
Lee WS, Chong VE, Victorino GP. Computed Tomographic Findings and Mortality in Patients With Pneumomediastinum From Blunt Trauma. JAMA Surgery. 2015
Caceres M, Ali SZ, Braud R, Weiman D, Garrett HE. Spontaneous Pneumomediastinum: A Comparative Study and Review of the Literature. Annals of Thoracic Surgery. 2008. PMID 18721592
Wald L, Yergin C, Petroze R, Larson S, Islam S. The Unnecessary Workups and Admissions of Adolescents and Young Adults With Spontaneous Pneumomediastinum. Scientific Reports. 2024. PMID 38402248
Additional references
Supporting and imaging literature
Kouritas VK, Papagiannopoulos K, Lazaridis G, et al. Pneumomediastinum. Journal of Thoracic Disease. 2015. PMID 25774307
Mendes J, Boas NV, Gomes C, Santos SD. Hamman Sign and Syndrome: A Reminder of Important Clinical Clues. Pediatric Pulmonology. 2025
Ebina M, Inoue A, Takaba A, Ariyoshi K. Management of Spontaneous Pneumomediastinum: Are Hospitalization and Prophylactic Antibiotics Needed? American Journal of Emergency Medicine. 2017. PMID 28330688
Bejvan SM, Godwin JD. Pneumomediastinum: Old Signs and New Signs. AJR American Journal of Roentgenology. 1996. PMID 8615238
Yamamichi T, Ibuka S, Yamashita S, et al. Surgical Drainage of Tension Pneumomediastinum in a Newborn: A Rare Lifesaving Intervention. Pediatric Pulmonology. 2025
Expert Panel on Pediatric Imaging, Dorfman SR, Chan SS, et al. ACR Appropriateness Criteria Chest Pain-Child. Journal of the American College of Radiology. 2026
Prevost B, Leger PL, Sileo C, et al. Spontaneous Pneumomediastinum: A Complication of SARS-CoV-2 Variant Delta Infection in Children. Pediatric Pulmonology. 2024
Takada K, Matsumoto S, Hiramatsu T, et al. Management of Spontaneous Pneumomediastinum Based on Clinical Experience of 25 Cases. Respiratory Medicine. 2008. PMID 18585025
Koullias GJ, Korkolis DP, Wang XJ, Hammond GL. Current Assessment and Management of Spontaneous Pneumomediastinum: Experience in 24 Adult Patients. European Journal of Cardio-Thoracic Surgery. 2004. PMID 15082293
SymptomDx is an educational tool for medical professionals. It does not replace clinical judgment. Verify all clinical data and drug dosages with authoritative sources.