A fifteen-year-old male presented at 0100 to the local emergency department complaining of increasing dyspnea, chest pain and a sore throat. He denied any nasal discharge, cough, nausea or vomiting. His symptoms had started the previous afternoon on the first day of football practice. He had been running 24 100-yard sprints as a conditioning exercise, and about 2/3-way through, he started becoming symptomatic. There had been no contact drills. He had been able to complete the exercise, but his symptoms continued to worsen throughout the evening. He never had a similar episode. He did not recall any Valsalva-like maneuvers, nor did he lift any weights. 
He denied being a smoker and had no past history of asthma, respiratory problems, or other significant health issues. He denied any illicit or recreational drug use.
On exam, the patient was a 6'3'', 270 lbs, large teenager who appeared slightly dyspneic, but not distressed. Blood pressure was 128/70, heart rate 80, respiratory rate 28, and temperature 97.8 F; SaO2 was 97% on room air. HEENT exam was unremarkable, and the oral cavity showed normal appearing tonsils and a midline uvula. Speech was normal sounding, with no nasal quality. There was no erythema and no exudates. There was no subcutaneous emphysema or crepitus in the neck or the chest area. Lungs were clear to auscultation bilaterally with no adventitial lung sounds. CV showed a regular rate and rhythm with no murmurs, clicks, gallops, or extra heart sounds, specifically no systolic crepitations. Abdomen was benign, and the rest of the exam was unremarkable.
Chest X-ray (Figure 1) showed subcutaneous emphysema, with air tracking into the neck area bilaterally, and a para-aortic air stripe of the left. There was also evidence of a minimal left apical pneumothorax (PNX). The trachea was midline, and the remainder of the lung fields and cardiac silhouette were normal.
The patient was diagnosed with pneumomediastinum and transferred to a tertiary care facility where he was admitted, placed on high flow oxygen, and observed. Later that morning, he was still noted to be dyspneic and complaining of chest pain. The following morning, the patient was asymptomatic, and was discharged. At a followup visit to his pediatrician 2 weeks later, the chest X-ray (Figure 2, expiration view) showed complete resolution of his previous lung findings, and he was given clearance to return to physical activity.