I've taught the "rear naked choke hold" in class on numerous occasions, stressing its effectiveness and relative safety.
A study posted on a Judo-website lists a number of cases of people dying from choke holds. In most cases the deceased were intoxicated (e.g. drugs), or had heart disease or hypertension. At the end of the article a couple of guidelines are listed. Please scan the article and read the guidelines at the end.
Another article suggests not:
- To perform a "choking" hold on subjects with cardiac disorders or hypertension.
- To apply "choking" on youngsters whose central nervous system and heart have not yet attained complete development.
- To continue to hold after the subject falls unconscious.