A Case of Pneumomediastinum

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A Case of Pneumomediastinum: A Medical Student Clinical Pearl

Reviewed by Dr. Maria Kovalik

Copyedited by Dr. Mandy Peach

 

Nick Ellingwood, Med II

Dalhousie Medicine New Brunswick (DMNB)

 

Case

A 16 year-old male presented to the emergency department complaining of shortness of breath which started 3 days prior. He stated that he was unable to take a deep breath. The patient described a sore throat with a productive cough. The patient also revealed that he was having some generalized chest tightness which did not radiate and was non-pleuritic. The patient was also experiencing some diarrhea as well as nausea when he eats. The patient denied any abdominal pain, vomiting, dysphagia, or fever. He had no past medical or surgical history and taking no medications.

On Examination:

Vitals: Temp=36.7oC, HR=126, RR=24, BP=100/62, O2 Sat=95% The patient was sitting comfortably but did appear to be dyspneic.  He was of normal body habitus.

On examination, upon palpation there was crepitus in the lower neck, supraclavicular region, and shoulder region on both sides. There was diffused crackles upon auscultation over the anterior and posterior chest wall. Good air entry into the base of both lungs and no wheezing. There was a normal S1 and S2 with no additional heart sounds or murmurs. Abdomen was soft and non-tender with normal bowel sounds.

A nasopharyngeal swap, chest X-ray, cervical X-ray, CBC, electrolytes, creatinine, urea, random glucose were ordered.

Figure 1. Chest X-ray showing extensive subcutaneous emphysema along the chest wall and lower neck and a pneumomediastinum. There is bilateral perihilar opacities but no pneumothorax or pleural effusion.

Figure 2. Cervical X-rays showing subcutaneous emphysema in the supraclavicular and lower neck regions as well as the retropharyngeal region extending beyond the angle of the mandible.

Etiologies of Pneumomediastinum1,2:

  • Acute asthma exacerbations
  • Covid-19 or other lower respiratory infections
  • Injury to thoracic cavity or airways from surgery, trauma, inhalation of drugs, or Valsalva maneuvers
  • Perforated esophagus (Boerhaave syndrome)

 

Case Continued:

A CT chest was ordered to evaluate the extent of the pneumomediastinum and subcutaneous emphysema and rule out severe etiologies such as esophageal and bronchi rupture which were not present. The nasopharyngeal swap came back negative for Covid-19 but positive for another coronavirus. The bloodwork showed leukocytosis (25×109/L) but was otherwise unremarkable. The diagnosis of pneumomediastinum secondary to coronavirus infection was made.

Pathophysiology:

As seen in Figure 3, a pneumomediastinum can result from air escaping from small alveolar ruptures into the surrounding bronchovascular sheath. Air then travels along a pressure gradient through the bronchovascular sheath to the hilum and builds up in the mediastinum.3 From there, air can freely move subcutaneously to the chest wall, upper limbs, and neck. Less commonly, air will directly escape into the mediastinum from a more central structure such as the upper respiratory tract or the esophagus.

Figure 3. Pathophysiology of pneumomediastinum and subsequent subcutaneous emphysema.

https://www.uptodate.com/contents/image/print?imageKey=PEDS%2F111129&topicKey=6352&search=pneumomediastinum&rank=1~111&source=see_link

 

Additional Exam Findings:

Hamman’s sign is described as a crunching or rasping sound heard over the precordium that is synchronous with systole and tends to be best heard with the patient in the left lateral decubitus position. This sign can be positive in up to 50% of patients with pneumomediastinum and is specific for pneumomediastinum or pneumopericardium4,5.

PoCUS Findings:

Firstly, in a pneumomediastinum the visualization of the cardiac structures is commonly obstructed by the presence of an “air gap” which is characterized by diffused A-lines anterior to the heart when in the parasternal and apical views. This can also be present in pneumothorax; however, the key difference is that in a pneumothorax the cardiac structures will be visualize during diastole when the heart dilates and pushes the pleural air to the side. In a pneumomediastinum, the air gap will vary with the respiratory cycle (not the cardiac cycle such as in a pneumothorax) because during inspiration the lungs will expand and push the air in the mediastinum cranially allowing the cardiac structures to be visualized6.

There are other clinical tools that can be used to differentiate a pneumomediastinum and a pneumopericardium like ECG changes. However, they can also be easily differentiated using PoCUS because the cardiac structures can’t be visualized in the subxiphoid view in a pneumopericardium. In contrast, the absence of air between the diaphragm, pericardium and myocardium allows the cardiac structure to be visualized in the setting of a pneumomediastinum as seen in Figure 47.

Figure 4. PoCUS images showing a pneumomediastinum where box A (subxiphoid view) shows cardiac structures. The parasternal long (B), parasternal short (C), and apical (D) views all show diffuse A-lines suggesting the presence of the air superficial to the heart. These findings would suggest a pneumomediastinum7.

 

Treatment:

  • Pneumomediastinum normally follows a benign course and is self-limiting
  • Some patients undergo bronchoscopy or esophagogram to rule out airway or esophageal injury
  • Admission is recommended to observe for complications because pneumopericardium and pneumorachis can arise8,9
  • Supplemental oxygen is given to help promote gas reabsorption
  • Simple analgesics are used for pain management as needed

 

Case Conclusion:

The patient was on 4L/min of oxygen while in hospital, and his symptoms significantly improved. Repeat chest X-ray showed improvement in pneumomediastinum and subcutaneous emphysema and he was discharge after 3 days. A chest X-ray 10 days later showed minimal subcutaneous emphysema, and the patient had no symptoms.

Clinical Pearls:

  • Pneumomediastinum is rare but something to keep in your differential for chest pain and SOB especially in young thin males
  • There are some life-threatening etiologies of pneumomediastinum that must be ruled out
  • There are some specific PoCUS findings for pneumomediastinum that can help with your diagnosis
  • The treatment for pneumomediastinum is rest, simple analgesics, and oxygen

 

References:

1: Ojha S, Gaskin J. Spontaneous pneumomediastinum. BMJ Case Rep. 2018;2018:bcr2017222965. Published 2018 Feb 11. doi:10.1136/bcr-2017-222965

2: Spontaneous pneumomediastinum in children and adolescents – UpToDate [Internet]. [cited 2021 Dec 17]. Available from: https://www.uptodate.com/contents/spontaneous-pneumomediastinum-in-children-and-adolescents?search=pneumomediastinum&source=search_result&selectedTitle=1~111&usage_type=default&display_rank=1

3: Ivan Macia, Juan Moya, Ricard Ramos, Ricard Morera, Ignacio Escobar, Josep Saumench, Valerio Perna, Francisco Rivas, Spontaneous pneumomediastinum: 41 cases, European Journal of Cardio-Thoracic Surgery, Volume 31, Issue 6, June 2007, Pages 1110–1114

4: 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. doi: 10.4103/1947-2714.117296. PMID: 24083220; PMCID: PMC3784922.

5: Alexandre AR, Marto NF, Raimundo PHamman’s crunch: a forgotten clue to the diagnosis of spontaneous pneumomediastinumCase Reports 2018;2018:bcr-2018-225099.

6: Ng L, Saul T, Lewiss RE. Sonographic evidence of spontaneous pneumomediastinum. Am J Emerg Med. 2013 Feb;31(2):462.e3-4. doi: 10.1016/j.ajem.2012.08.019. Epub 2012 Nov 15. PMID: 23158605.

7: Zachariah, S., Gharahbaghian, L., Perera, P., & Joshi, N. (2015). Spontaneous pneumomediastinum on bedside ultrasound: case report and review of the literature. The western journal of emergency medicine, 16(2), 321–324. https://doi.org/10.5811/westjem.2015.1.24514

8: Vanzo V, Bugin S, Snijders D, Bottecchia L, Storer V, Barbato A. Pneumomediastinum and pneumopericardium in an 11-year-old rugby player: a case report. J Athl Train. 2013 Mar-Apr;48(2):277-81. doi: 10.4085/1062-6050-48.1.11. Epub 2013 Feb 20. PMID: 23672393; PMCID: PMC3600931.

9: Belotti EA, Rizzi M, Rodoni-Cassis P, Ragazzi M, Zanolari-Caledrerari M, Bianchetti MG. Air within the spinal canal in spontaneous pneumomediastinum. Chest. 2010 May;137(5):1197-200. doi: 10.1378/chest.09-0514. PMID: 20442120.

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