angelikaJ -> RE: Breathe play questions and thoughts (10/9/2008 11:52:32 AM)
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http://members.aol.com/Oldrope/breath.htm (from same article by Jay Wiseman) "...As a person with years of medical education and experience, I know of no way whatsoever that either suffocation or strangulation can be done in a way that does not intrinsically put the recipient at risk of cardiac arrest. (There are also numerous additional risks; more on them later.) Furthermore, and my *biggest* concern, I know of no reliable way to determine when such a cardiac arrest has become imminent. ... Quick pathophysiology lesson # 1: When the heart gets low on oxygen, it starts to fire off "extra" pacemaker sites. These usually appear in the ventricles and are thus called premature ventricular contractions -- PVC's for short. If a PVC happens to fire off during the electrical repolarization phase of cardiac contraction (the dreaded "PVC on T" phenomenon, also sometimes called "R on T") it can kick the heart over into ventricular fibrillation -- a form of cardiac arrest. The lower the heart gets on oxygen, the more PVC's it generates, and the more vulnerable to their effect it becomes, thus hypoxia increases both the probability of a PVC-on-T occurring and of its causing a cardiac arrest. ... Some people teach that choking can be safely done if pressure on the windpipe is avoided. Their belief is that pressing on the arteries leading to the brain while avoiding pressure on the windpipe can safely cause unconsciousness. The reality, unfortunately, is that pressing on the carotid arteries, _exactly_ as they recommend, presses on baroreceptors known as the carotid sinus bodies. These bodies then cause vasodilation in the brain, thus there is not enough blood to perfuse the brain and the recipient loses consciousness. However, that's not the whole story. Unfortunately, a message is also sent to the main pacemaker of the heart, via the vagus nerve, to decrease the rate and force of the heartbeat. Most of the time, under strong vagal influence, the rate and force of the heartbeat decreases by one third. However, every now and then, the rate and force decreases to zero and the bottom "flatlines" into asystole -- another, and more difficult to treat, form of cardiac arrest. There is no way to tell whether or not this will happen in any particular instance, or how quickly. There are many documented cases of as little as five seconds of choking causing a vagal-outflow-induced cardiac arrest. ..."
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