[365seasons]

I wouldn't worry too much. Pouch emphysema is a very common occurrence in male seahorses. My husband and I have dealt with this many times.

Is he bouyant, and floating at the top? Because that would be your first worry, as he is unable to get food. Burping the pouch is the easiest way, but is a short term fix for the most part. And if you do it to much, you will cause trauma to the stomach.
To burp the pouch, just hitch the male seahorse around a finger so you have a firm grip of him, upwards in the water, and using your index and thumb finger, gently massage from the base of his tail up to his pouch. This should release a stream of air bubbles when he opens up. If air doesn't come out this way, you can also use a small blunt object to try and tickle his opening up. a bobby pin works great, and don't try to stick it it, just tease it, and it should open up and allow the air to come out when you burp.

Probably the best thing you can do is give him some Diamox, if you can get your hands on it. This can be given orally (mysis with it-most effective) as a bath, or as a pouch wash. A pouch flush is when you use a catheter and a small syringe (you can get them from the drug stores) and you flush the pouch out. This seems painful, but really isn't.

Another method that I have had great success with, and is not as hard as it may seem is a needle aspiration.
All you need is a small hypodermic needle (again,drug store) which you insert into the SIDE of the pouch as to not cause trauma to the front. Depress the plunger to suck up some air, and then release it (it will not release just by puncturing the pouch) Do this on both sides. Again, we've had great success releasing air from a brood pouch with this method.

Pete Giwonja on the seahorse.com forum boards can give you WAY more detailed descriptions on how to do any of these procedures, and usually gets back to you within the day. He is a master of seahorses as far as I'm concerned.

Hopefully I have been of some help, and if you have any questions, I will try to ask them. Good luck!!