Compression damage to nerves is a possibility. AIDS risks in bondage per se are practically nonexistent except if the bonds have previously been exposed to blood, semen, or other body contaminants and not been sterilized. Contaminated ropes can be discarded. When such is not possible, a thorough soaking with alcohol or hydrogen peroxide prior to the next usage will probably suffice. The health risks in breath control scenes are obvious.
Problems can develop fast.
If the brain is starved for oxygen long enough the subject may not die, but brain damage may occur. Because of the potential dangers, such practices should be investigated thoroughly during any history taking. The potential for lethality increases dramatically when coupled with bondage. One important thing to keep in mind here is that it may be the dangerous part of the scene that provides the erotic excitement. For some, the thrill is the knowledge that one's life is, breath by breath, in the hands of another who must, moment to moment, be responsible for a particular life.