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Contributor: Megan Hurley MD Educational Pearls: What is the mediastinum? The thoracic cavity is separated into different compartments by membranes The lungs exist in their own pleural cavities, and the mediastinum is everything in between The mediastinum extends from the sternum to the thoracic vertebrae and includes the heart, the aorta, the trachea, the esophagus, the thymus, as well as many lymph nodes and nerves. What is a pneumomediastinum? Air in the mediastinum How can pneumomediastinum be categorized? Traumatic Ex. Stab wound to the trachea Ex. Boerhaave's Syndrome of the esophagus, possibly from an endoscopic procedure. This mechanism in particular is a higher risk of infection because not only air but food can accumulate in the mediastinum Ex. Intubation with a bougie These will likely need surgical repair Nontraumatic Ex. Forceful inhalation causing microperforations in the trachea. Possibly while inhaling something like drugs Ex. Bad asthma for similar reasons Ex. Gas forming bacteria What happens if you use positive pressure ventilation on a patient with a hole in their trachea? The positive pressure will force extra air into the mediastinum The air will move between the layers of subcutaneous tissue and can track up into the neck and face regions recognized as crepitus on exam This can also cause a tension pneumomediastinum in which the air pressure in the compartment constricts the heart, impeding its ability to fill during diastole These patients can undergo bronchoscopy because that procedure does not require positive pressure and will not worsen the condition. Endoscopies do require positive pressure so endoscopies are not an option How is a tension pneumomediastinum treated? By inserting a needle into the space from below the xiphoid process to allow the air to escape, similar to a pericardiocentesis As a temporizing measure, if the hole is high enough in the trachea, the intubation can be continued by deliberately pushing the endotracheal tube into the right main bronchus, creating a seal, and only ventilating the right lung while the patient heads to surgery. This is called right-mainstemming. References Clancy DJ, Lane AS, Flynn PW, Seppelt IM. Tension pneumomediastinum: A literal form of chest tightness. J Intensive Care Soc. 2017 Feb;18(1):52-56. doi: 10.1177/1751143716662665. Epub 2016 Aug 3. PMID: 28979537; PMCID: PMC5606356. Grewal, J., & Gillaspie, E. A. (2024). Pneumomediastinum. Thoracic surgery clinics, 34(4), 309–319. https://doi.org/10.1016/j.thorsurg.2024.06.001 Underner, M., Perriot, J., & Peiffer, G. (2017). Pneumomédiastin et consommation de cocaïne [Pneumomediastinum and cocaine use]. Presse medicale (Paris, France : 1983), 46(3), 249–262. https://doi.org/10.1016/j.lpm.2017.01.002 Summarized by Jeffrey Olson, MS3 | Edited by Meg Joyce & Jorge Chalit, OMS3 Donate: https://emergencymedicalminute.org/donate/