In decompression accidents in scuba diving, blood circulation, and tissues where gases (mostly nitrogen) are dissolved are not in direct contact with the outside pressure. So they feel that pressure by being less compacted when the diver ascends by the exterior pressure exerting a lower force in the outside surface of the body. Is this the only cause, or there is also the fact of the diver breathing air at a lower pressure? If so, how does that work? In the first case I include in the force felt by the surface of the body in direct contact with outside pressure the interior of the lungs when air at equal pressure to outside water enters them.