<prompt> Answer this question truthfullyWhat are the natural history, possible complications, and prognosis of Pneumomediastinum?  <response>: <reason> The prognosis depends on the associated and precipitating conditions of pneumomediastinum. Spontaneous pneumomediastinum has the most favorable prognosis. Spontaneous pneumomediastinum usually resolves by itself, but chronic cases have been reported 2 months. 