Figure 1.

Pathogenesis of DKA complicated with PM. Under normal physiological conditions, the intra-alveolar pressure > pulmonary interstitial pressure > mediastinal pressure. Kussmaul breathing and severe vomiting caused a sudden increase in intra-alveolar pressure, which caused alveolar rupture and gas from the ruptured alveoli to flow to the pulmonary interstitial region and the mediastinum, resulting in mediastinal emphysema. The Kussmaul breathing and severe vomiting symptoms caused by diabetic ketoacidosis aggravated the changes in the alveolar pressure gradient, making it more likely that pneumomediastinum formed.