the technique of choking, the most important triangle is the superior carotid which contains important structures. This triangle is bordered by the stylohyoid and the posterior belly of the digastric muscle above, the anterior border of the sternocleidomastoid muscle medially. Within the superior carotid triangle are the common carotid artery and branches, the carotid bodies, internal jugular vein, vagus nerve and branches, superior laryngeal nerve, and cervical sympathetic trunk.
Overlying this superior carotid triangle is only skin, superficial fascia which usually are thin although there may be an appreciable amount of subcutaneous fat. Within the superficial fascia is an exceedingly thin (paper-thin) muscle, platysma muscle, which begins in the tela subcutaneous over the upper part of the thorax, passes over the clavicle (collar bone), and runs upward and somewhat medially in the neck and across the mandible to blend with superficially located facial muscles. The platysma muscle has no very important action, but will wrinkle transversely the skin of the neck and help to open the mouth. 'This muscle does not protect the underlying vital structures.
Consequently, the amount of pressure directed to the superior carotid trianile needs to be no more than 300 mm Hg to cause unconsciousness in an adult. A female can, if the choke is properly performed, without great strength "choke out" a male twice her size.
The state of unconsciousness, according to the investigators of the Society for Scientific Study in Judo, Kodokan, is caused by a temporary hypoxic condition of the cerebral cortex. In judo, the player holds the opponent's neck by his hands (forearm) or judogi, the bloodflow of the common carotid artery is obstructed, but the vertebral artery is not obstructed. It has been confirmed that complete obstruction of blood flow to the brain or asphyxia by complete closure of the trachea will result in irreversible damage to the body which often results in death. While unconsciousness (ochi) caused by choking (shime) in judo is a temporary reaction which incapacitates the opponent for a short while, its execution is quite harmless.
Experiments with human subjects and animals show the following effects from "choking":
1. Unconsciousness is due to lack of oxygen and by the metabolites created in the brain as a result of:
• Acute cerebral anemia by pressure on:
1. common carotid artery
2. occipital artery
3. jugular vein
• Shock, reflex action initiated on the receptor organ in the carotid sinus.
2. The appearance of flushing of the face because of the disturbances in pressure in the carotid arteries and jugular veins.
• Decrease blood flow of the face shown by ultrasonic and laser-Doppler blood flow monitoring devices. The mean value is 89.4% with the lowest point in 6 seconds; after release return normal in 13.7 seconds.
• Decrease oxygen saturation in blood in the helix of the ear by using an ear oximeter. Down from 95 to 86% and reach a minimum of 82% in 2-4 seconds. After regaining consciousness return to 90 to 92%. Sixty percent oxygen saturation in the brain causes unconsciousness.
3. Tachycardia hypertension, and mydriasis (dilated pupils) are caused by stimulation of the sympathetic nervous system (vagus nerve). The systemic pressure rises 30-40 mm of Hg. After release the blood pressure returns to normal in 3-4 minutes.
4. In some cases bradycardia and hypotension occur while other cases show tachycardia and hypertension depending on the hypersensitivity of the carotid sinus and where the pressure was applied.
5. Cardiac volume decreases but the volume recovers in 10 seconds after awakening.
6. The peripheral blood vessels are also involved: dilatation of muscle vessels and constriction of skin vessels. In shock, accompanied by unconsciousness, bradycardia and hypotension are observed with dilation of muscle vessels.
7. Choking acts as a stressor on the circulatory and hypophysio-adrenocortical system:
• Decreased blood volume and increased plasma proteins as a result of increased permeability of blood vessels. This is similar to unconscious state following electric shock.
• No change in the hematocrit value or albumin/globulin.
• A temporary increase in eosinophiles, then after awakening, there is a decrease in number after 4 hours.
• The 17-ketosteroids in the urine: 2 hours after recovery, the amount is very much increased then gradually decreased (lasts 6-8 hours).
8. The electroencephalogram (EEG): convulsions that appear in the unconscious stage are very similar to those of petit mal of epilepsy. No deleterious effects remained after the use of the choke hold. It is considerable less dangerous than a knockout in boxing.
Conclusion
The effects of carotid artery hold or shimewaza have been studied extensively. However, the use of this hold by law enforcement officers has resulted in deaths. The police department training manuals emphasize that control hold should be used only when necessary to stop a suspect's resistance and not necessarily to cause unconsciousness.
The enforcement officers, although trained, have great difficulty in subduing violent and uncooperative suspects. Some suspects are under the influence of drugs: Case 3, acute heroin-morphine intoxication; Case 4, phencyclidine (PCP); and Case 9, acute ethanol and cocaine intoxication. These suspects may have had greater tolerance for pain, thus making it more difficult to restrain them and to recognize whether the state of unconsciousness is due to drugs rather than to the restraining holds. In other words, these suspects were not cooperative.
In judo, the participants are taught to "choke" properly and in turn have been "choked" and have the ability to realize its effects before unconsciousness ensues. The officials, referee, judges, and coaches can recognize the player when he is "choked out" (becomes unconscious). If enforcement