4 week old chick with huge air pockets!
This sounds like subcutaneous emphysema or leaking air sacs caused by blunt trauma. If you can get a needle (22 gauge down to 18 gauge) from a feed store, you can puncture just under the skin, leave the needle in place, and push the air out, then hold the puncture site for a bit to try to seal it. Apply neosporin.or bacitracin ointment (or even vaseline, if that's all you have.) You may have to puncture more than one site, and it may come back again. Let us know how it is, and here are some articles to read:
Air sacs in chickens
Edited by Eggcessive - 4/9/16 at 12:44pm
Those may be too small since they are probably 25 to 27 gauge. 22 gauge is small, but it has worked for me. You can try, but maybe a sterilized sewing needle could be used carefully. When the leaking air sac is so extensive as yours sounds, the chick may have trouble breathing, but i hope that you can save it.