Final answer:
The next action would be to refer Max to an ear, nose, and throat specialist who can provide appropriate treatment and advice for his barotrauma.
Step-by-step explanation:
The next action in this case would be to refer Max to an ear, nose, and throat specialist. Barotrauma occurs when there is a sudden change in pressure, such as during air travel. It can cause damage to the middle ear, leading to symptoms like pressure and pain. Since Max has been diagnosed with barotrauma, it is best to have him evaluated by a specialist who can provide appropriate treatment and advice.