Comixx,

a choke hold is a slightly different case. In the event of cardiac arrest, or dysrhythmia such as ventricular fib or tach, the blood pressure drops to zero ( or near enough as to not matter.) an experiment to illustrate: (caution: professionals at work. DO NOT try this at home!) Go without water for two days to get good and dehydrated. Lie down for 30 minutes, then jump up to a standing position, and see how long it takes to pass out. Only a second or two. Even the tightest choke hold cannot block the flow of the vertebral arteries, so the BP at the brain won't drop all the way to zero. (Exception -- older people with significant blockages of the vertebrals, but they would pass out in just a few seconds. )

Blood pressure is the factor in conciousness, not oxygen. The brain can survive about four minutes without oxygen, but cannot maintain conciousness without blood pressure for more and 2-3 seconds.

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I am a doctor, but I don't play one on TV.