Chokes are applied either against the windpipe (trachea) to cut off the air supply to the lungs or to damage it so the air supply will be interrupted or stopped (air chokes) or to one or both of the carotid arteries to cutoff blood flow, and thus oxygen supply, to the brain (blood chokes or strangles). They can be very effective if applied at the proper time. If you suddenly apply a choke to unsuspecting person, it will take a relatively long time to take affect and, due to the defensive efforts of the victim, will probably fail. If the attacker is larger in size and stronger than the victim, the choke may be successful. Pressure to the windpipe is usually applied with the forearm or a stick type object.
Chokes can also be applied by compressing the chest and lungs, thus preventing the opponent from inhaling (often used during pinning techniques). When used in combination with an air or blood choke, compression chokes may increase their effectiveness.
Shutting off respiration may bring about changes of a reflex nature which may cause serious heart and respiratory reactions. Shutting off the air intake may cause an inadvertent valsalva maneuver (forced expiration with the glottis closed), which will set in motion other reflex changes and cardiovascular effects resulting in dangerous and even irreversible physiologic changes.