Diagnostics and Therapeutics: Pneumomediastinum
/Pneumomediastinum is defined as the presence of air in the mediastinum after rupture of air-filled structures such as the esophagus or trachea, or small parts of the lung such as alveoli. This can occur spontaneously or after trauma. Pneumomediastinum is often benign and self limited. However, in more serious cases it can require close monitoring and sometimes surgical intervention. This post describes the evaluation and treatment of this rare clinical entity.Additionally, with the presenting complaint being chest pain, the differential diagnosis early in work up can include far more serious conditions like myocardial infarction or pulmonary embolism which the emergency physician should keep in consideration.
What is the mediastinum anyway and how does air get in it?
The mediastinum is the central compartment of the thoracic cavity, containing the heart, great vessels, trachea, esophagus, thymus, nerves and lymph nodes. Anteriorly, it is bordered by the sternum and costal cartilages and is adjacent to the vertebral column posteriorly. Superiorly, it extends to the thoracic inlet, and inferiorly, it is limited by the diaphragm. On either side, the mediastinum is bordered by the pleural cavities housing the lungs. When air enters this space, it tracks along tissue planes and is termed “pneumomediastinum” [1,2].
More specifically, the pathophysiology involves disruption of alveolar walls (alveolar rupture) or injury to larger airways or gastrointestinal structures, allowing air to leak into the mediastinum. Alveolar rupture typically results from sudden increases in intra-alveolar pressure, which can be caused by activities such as coughing, vomiting, or Valsalva maneuvers [4]. The air then follows the peri-bronchovascular sheaths into the mediastinum—a phenomenon known as the Macklin effect [5-7]. Alternatively, trauma or iatrogenic injury to structures such as the trachea, bronchi, or esophagus can result in direct leakage of air into the mediastinum [5].
Epidemiology and etiology
Pneumomediastinum is uncommon. Reported prevalence varies significantly in the literature, with is a reported prevalence as low as 0.00002% and as high as 0.001%. In adult emergency room visits, its incidence is around 1 in 25,000 (0.00004%) and is slightly higher in pediatric emergency room visits at rates of around 0.3-5% [19]. This post is focused on adult cases of pneumomediastinum.
Pneumomediastinum is often divided into two categories - spontaneous and traumatic. Spontaneous cases typically occur in younger, tall males with a low body mass index, accounting for 50-75% of instances [2]. As prognosis is often driven by the degree of a patient’s underlying lung disease, some experts will further distinguish the spontaneous category into primary (in which there is no underlying lung disease at all and usually has the best prognosis) and secondary (in which there is some underlying lung disease such as cystic fibrosis, asthma, COPD, pulmonary fibrosis, pneumonia, etc).
Spontaneous Pneumomediastinum (SPM):
-Occurs without external trauma or significantly identifiable disease.
-Most common triggers include respiratory conditions such as asthma, COPD, and pneumonia which can lead to forceful coughing
-Other common triggers include forceful exertion, severe coughing or vomiting, asthma exacerbation, intense physical activity, or Valsalva maneuvers (e.g., weightlifting, childbirth) [4].
-SPM is more common in young, healthy individuals, particularly males.
Secondary Pneumomediastinum:
-Caused by underlying conditions or external factors.
-Potential causes include:
-Trauma: Blunt or penetrating thoracic injuries, rib fractures, esophageal rupture (Boerhaave syndrome).
-Iatrogenic: Endotracheal intubation, mechanical ventilation, bronchoscopy, esophagoscopy, or dental procedures.
-Pulmonary disease: Severe asthma or chronic obstructive pulmonary disease (COPD) exacerbations.
-Infection: Necrotizing infections such as mediastinitis, gas-producing bacterial infections, or tuberculosis.
-Esophageal or tracheal rupture: These conditions can result in communication between the airway, esophagus, or mediastinum.
Clinical Presentation
The clinical manifestations of pneumomediastinum vary depending on the severity and underlying cause. In many cases, it is asymptomatic or has mild symptoms. The most common clinical features include [7-8]:
Chest pain (54-85% of cases): Retrosternal and sharp, worsened by deep inspiration or coughing.
Dyspnea (35-40% of cases): Varies from mild to severe, depending on the amount of air in the mediastinum and associated conditions (e.g., pneumothorax).
Neck pain or sore throat (5-35% of cases): Due to air tracking into the neck (subcutaneous emphysema).
Subcutaneous emphysema (32-70% of cases): Palpable crepitus in the neck or upper chest may be noted.
Voice changes (5% of cases): Dysphonia or hoarseness can occur if the recurrent laryngeal nerve is compressed.
Hamman’s sign: A crunching, crackling sound heard during auscultation that coincides with the cardiac cycle, caused by air moving in the mediastinal tissues.
In severe cases, especially those due to trauma or esophageal rupture, symptoms may progress to cardiovascular collapse, hypotension, or respiratory failure due to tension pneumomediastinum or pneumothorax [16].
Diagnosis
The diagnosis of pneumomediastinum is primarily made through imaging studies. A high index of suspicion is needed, especially in patients with chest pain and risk factors [7-8].
Chest X-ray: low sensitivity (as low as 26% in some studies) but can increase sensitivity by obtained lateral view x-ray
-The initial diagnostic tool of choice
-Classic signs include:
-Radiolucent streaks around the heart and great vessels
-Subcutaneous emphysema in the neck or thorax
-Naclerio’s V sign: V-shaped radiolucency along the left heart border due to air tracking from the mediastinum to the diaphragm.
Computed Tomograph (CT) Scan: more sensitive (100%) than chest x-ray and the gold standard for diagnosis (85% specific)
-Can detect small amounts of air in the mediastinum and delineate associated injuries (e.g., tracheal or esophageal perforation).
Esophagography or Bronchoscopy:
-May be warranted in cases where esophageal or tracheobronchial injury is suspected, especially if pneumomediastinum is secondary to trauma or Boerhaave syndrome [8-11].
Management
Treatment of pneumomediastinum depends on the underlying cause, the severity of symptoms, and the presence of associated complications such as pneumothorax or airway compromise [12-14].
Spontaneous Pneumomediastinum
Most cases of SPM are self-limiting and resolve without intervention and management is primarily conservative and includes:
Rest and observation: For asymptomatic or mildly symptomatic cases, close monitoring with serial chest X-rays is sufficient.
Analgesia: Pain control with nonsteroidal anti-inflammatory drugs (NSAIDs) or acetaminophen.
Oxygen therapy: Supplemental oxygen may accelerate the resorption of air.
Patients should be advised to avoid activities that increase intrathoracic pressure, such as heavy lifting or straining, during recovery.
Secondary Pneumomediastinum
Management focuses on addressing the underlying cause.
Trauma: Surgical consultation may be necessary for severe trauma cases, especially if tracheal, bronchial, or esophageal injury is suspected.
Esophageal perforation: Requires urgent surgical intervention and broad-spectrum antibiotics to prevent mediastinitis.
Infection: Appropriate antimicrobial therapy is indicated if an infectious etiology is identified.
Complications are more common with secondary pneumomediastinum and can include disease processes such as tension pneumomediastinum or pneumothorax. Sometimes these may require emergency interventions such as needle decompression or chest tube placement [8,13-14].
unique patient case from ucmc hospital. left image: extensive air tracking around the right paratracheal region and tracking around the left heart borders. right image: same patient, cy showing extensive anterior pneumediastinum.
Prognosis and Complications
The prognosis of pneumomediastinum is generally favorable, especially for spontaneous cases in young, healthy individuals. Most patients recover fully with conservative management. However, complications can occur, particularly in secondary pneumomediastinum, and include 3, 15-16]:
Tension pneumomediastinum: Air accumulation in the mediastinum leading to compression of cardiovascular structures, which can cause hemodynamic instability.
Pneumothorax: Concurrent air leakage into the pleural space, potentially leading to lung collapse.
Mediastinitis: A life-threatening infection of the mediastinum that can result from esophageal rupture or infectious pneumomediastinum [16].
Disposition
Spontaneous pneumomediastinum can be managed outpatient with a re-evaluation 24-48 hours after the initial presentation. Repeat imaging is rarely needed. It is recommend that patients avoid actions that raise pulmonary pressure, such as Valsalva maneuvers. Analgesia with NSAIDs and rest are encouraged.
Secondary cases are also often benign and self limited, however the underlying cause must be thoroughly understood and managed according to the pathology.
frequently asked questions
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As opposed to adults where spontaneous pneumomediastinum (SPM) can occur in up to 50% of cases without an obvious trigger, in children less than 6, SPM is very rare and the physician should consider looking for causes. For example, an occult foreign body can often cause SPM and should be considered for work up with bronchoscopy / esophagoscopy. Underlying undiagnosed asthma could also be a possible cause [20].
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Trauma patients are often at risk for significant injuries, especially in higher risk mechanisms of blunt trauma. If a patient with pneumomediastinum also has extensive diffuse subcutaneous emphysema, physicians should strongly consider more serious underlying injuries such as pleural or parenchymal lung injury causing pneumothorax [21].
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As described above, most patients with pneumomediastinum, regardless of the etiology, have a fairly benign course with ultimate resolution after conservative management. Therefore, most of these patients can be safely discharged with close outpatient followup with either their primary care physician or a pulmonologist. If their injury was from trauma, it would not be unreasonable to initiate trauma consult within the emergency visit, but also if the injury is isolated and the patient is well appearing, they could also follow up closely with the trauma clinic.
Alternatively, in patients who appear to be in distress, who are febrile, or who have clinical findings of extensive subcutaneous emphysema or objective findings of extensive air noted on CT scan, it would be reasonable to admit these patients with surgical consultation for further work up and possible decompressive management [16].
Conclusion
Pneumomediastinum is an important clinical entity that requires careful evaluation and management. While often benign and self-limiting, it can be associated with life-threatening conditions that necessitate prompt diagnosis and intervention. Maintaining a high index of suspicion, especially in at-risk populations, and utilizing appropriate imaging and diagnostic modalities to guide treatment strategies remains essential for Emergency Medicine physicians.
Post by Kenneth Valles, MD
Dr Valles is a PGY-1 in Emergency Medicine at the University of Cincinnati.
Editing by Anne Grisoli, MD and Anita Goel, MD
Dr Grisoli is a PGY-4 in Emergency Medicine at the University of Cincinnati and planning on pursuing an ICU fellowship following residency graduation.
Dr Goel is an Adjunct Assistant Professor in Emergency Medicine at the University of Cincinnati and an Assistant Editor of TamingtheSRU. She is a graduate from the UC EM residency, class of 2018.
References
1. Rizvi S, Wehrle CJ, Law MA. StatPearls [Internet]. StatPearls Publishing; Treasure Island (FL): Jul 24, 2023. Anatomy, Thorax, Mediastinum Superior and Great Vessels. [PubMed]
2. Al-Mufarrej F, Badar J, Gharagozloo F, Tempesta B, Strother E, Margolis M. Spontaneous pneumomediastinum: diagnostic and therapeutic interventions. J Cardiothorac Surg. 2008 Nov 03;3:59. [PMC free article] [PubMed]
3. Kouritas VK, Papagiannopoulos K, Lazaridis G, Baka S, Mpoukovinas I, Karavasilis V, Lampaki S, Kioumis I, Pitsiou G, Papaiwannou A, Karavergou A, Kipourou M, Lada M, Organtzis J, Katsikogiannis N, Tsakiridis K, Zarogoulidis K, Zarogoulidis P. Pneumomediastinum. J Thorac Dis. 2015 Feb;7(Suppl 1):S44-9. [PMC free article] [PubMed]
4. Lin YC. Pneumomediastinum after nose blowing. J Pediatr. 2015 May;166(5):1317-1317.e1. [PubMed]
5. Reha J, Davis P. Occult Pneumomediastinum in the Deployed Setting: Evaluation and Management. Mil Med. 2016 Aug;181(8):e959-61. [PubMed]
6. Gasser CR, Pellaton R, Rochat CP. Pediatric Spontaneous Pneumomediastinum: Narrative Literature Review. Pediatr Emerg Care. 2017 May;33(5):370-374. [PubMed]
7. Sahni S, Verma S, Grullon J, Esquire A, Patel P, Talwar A. Spontaneous pneumomediastinum: time for consensus. N Am J Med Sci. 2013 Aug;5(8):460-4. [PMC free article] [PubMed]
8. Banki F, Estrera AL, Harrison RG, Miller CC, Leake SS, Mitchell KG, Khalil K, Safi HJ, Kaiser LR. Pneumomediastinum: etiology and a guide to diagnosis and treatment. Am J Surg. 2013 Dec;206(6):1001-6; discussion 1006. [PubMed]
9. Zachariah S, Gharahbaghian L, Perera P, Joshi N. Spontaneous pneumomediastinum on bedside ultrasound: case report and review of the literature. West J Emerg Med. 2015 Mar;16(2):321-4. [PMC free article] [PubMed]
10. Beason HF, Markowitz JE. Pneumomediastinum Diagnosed on Ultrasound in the Emergency Department: A Case Report. Perm J. 2015 Summer;19(3):e122-4. [PMC free article] [PubMed]
11. Matthees NG, Mankin JA, Trahan AM, Israr S, Jones MD, Dameworth JL, Petersen SR, Weinberg JA. Pneumomediastinum in blunt trauma: If aerodigestive injury is not seen on CT, invasive workup is not indicated. Am J Surg. 2019 Jun;217(6):1047-1050. [PubMed]
12. Lee WS, Chong VE, Victorino GP. Computed Tomographic Findings and Mortality in Patients With Pneumomediastinum From Blunt Trauma. JAMA Surg. 2015 Aug;150(8):757-62. [PubMed]
13. Ebina M, Inoue A, Takaba A, Ariyoshi K. Management of spontaneous pneumomediastinum: Are hospitalization and prophylactic antibiotics needed? Am J Emerg Med. 2017 Aug;35(8):1150-1153. [PubMed]
14. Muckart DJJ, Hardcastle TC, Skinner DL. Pneumomediastinum and pneumopericardium following blunt thoracic trauma: much ado about nothing? Eur J Trauma Emerg Surg. 2019 Oct;45(5):927-931. [PubMed]
15. Olson RP. Return to collision sport after pneumomediastinum. Curr Sports Med Rep. 2012 Mar-Apr;11(2):58-63. [PubMed]
16. Iteen AJ, Bianchi W, Sharman T. Pneumomediastinum. [Updated 2023 May 1]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557440/
17. Caceres, Manuel et al. Clinical Pearls in Nonpenetrating Pneumomediasteinum. CHEST, Volume 130, Issue 4, 270S
18. Dissanaike S, Shalhub S, Jurkovich GJ. The evaluation of pneumomediastinum in blunt trauma patients. J Trauma. 2008 Dec;65(6):1340-5. doi: 10.1097/TA.0b013e318169cd24. PMID: 19077624.
19. Alishlash, Ammar Saadoon, and Ibrahim A Janahi. “Spontaneous Pneumomediastinum in Children and Adolescents.” Uptodate, 9 Feb. 2024, www.uptodate.com/contents/spontaneous-pneumomediastinum-in-children-and-adolescents?search=pneumomediastinum&source=search_result&selectedTitle=1%7E111&usage_type=default&display_rank=1.
20. Wong KS1, Wu HM, Lai SH, Chiu CY. Spontaneous pneumomediastinum: analysis of 87 pediatric patients. Pediatr Emerg Care. 2013 Sep;29(9):988-91. PMID: 23974718.
21. Dehours E., Vallé B., Bounes V., Lauque D. A pneumomediastinum with diffuse subcutaneous emphysema. Journal of Emergency Medicine. 2013;44(1):e81–e82. doi: 10.1016/j.jemermed.2011.08.023. [DOI]
