What tests need to be done to further define the condition(Pneumothorax or Pneumomediastinum)?

An X ray of the chest is the test that absolutely confirms that a pneumothorax or pneumomediastinum is present. It can also provide some information as to how much air and compression on the lungs has occurred. Prior to the chest X ray, you may be able to suspect an air leak by listening to the chest and hearing decreased breath sounds on the side with the leak. You can also place a light on the front of the chest (transillumination), which may indicate air has leaked out of the lung and accumulated in the chest.