Hamman's syndrome, also known as Macklin's syndrome, is a syndrome of spontaneous subcutaneous emphysema[1] (air in the subcutaneous tissues of the skin) and pneumomediastinum (air in the mediastinum, the center of the chest cavity), sometimes associated with pain and, less commonly, dyspnea (difficulty breathing), dysphonia, and a low-grade fever.

Excessive duration and/or intensity of activities that mimic valsalva manoeuvres, i.e. that increase intrathoracic pressure, can cause barotrauma, and hence pregnancy (and constipation and other causes of excessive straining) can be a precipitating cause of Hamman's syndrome.

Indeed, it is estimated to occur in approximately 1 in 100,000 live births and is associated with prolonged labour times.

[2] Additionally, vomiting and coughing have also been noted as occasional precipitating factors.

It is important to differentiate it from far more serious conditions that have similar symptoms, such as Boerhaave's syndrome.