Friday, January 11, 2013

Shime Waza and Neck Restraints - Update of the Update

I previously posted a post on shime waza/neck restraints and then posted an update on that post. This post is an update on that update.

In the update, I referred to a study - Mechanism of loss of consciousness during vascular neck restraint - published in the Journal of Applied Physiology. A Force Science News article expressed views that this study was the definitive study on shime waza/neck restraints that target the lateral aspects of the neck. In my post, I suggested that the authors did not address the issue of jugular vein occlusion which the Pi panel had suggested was more important than carotid artery occlusion in the loss of consciousness. They did not.

I contacted one of the authors of the study concerning this issue. They generously replied to my correspondence and informed me why. As it turns out, the study is a definitive study, they just don't do a very good job of establishing the definitive nature. You have to work to appreciate that definitive nature.

The Pi panel base their argument on three legs. Firstly, on a study by Reay and Matthews which involved five FBI Special Agents. Not surprising given that Pi, in addition to being an MD is also an FBI Special Agent. This study is in no way conclusive, however, this in itself does not invalidate the Pi conclusions. Secondly, they rely quite heavily on the fact that it takes more pressure to occlude the carotid arteries than the jugular veins. They suggest that venous occlusion halts the cerebral circulation with the net effect being similar to the occlusion of the forward blood flow of the carotid arterial system. What happens when the arterial and venous blood flow are restricted? They are silent on that issue. Thirdly, their argument relies heavily on the presence of petechiae. Ely and Hirsh clearly demonstrate that conjunctival and facial petechiae are the product of purely mechanical vascular phenomena, unrelated to asphyxia or hypoxia. The loss of consciousness appears to be related to carotid artery occlusion while petechiae appears to be related to venous occlusion after a relatively prolonged period of time. The Pi panel fail to provide any reference for the clinically ‘observed’ petechiae with carotid restraint techniques.

The Mitchell et al study is definitive. They, and the Force Science article, simply do a poor job of promoting the definitive nature of the study.

As an aside, I love this world. This world where you study, research, think, apply, develop ideas. Where you talk to like-minded individuals who are so generous with their time and are happy to share their work with you. You have to do the requisite work beforehand, however, having done that they are, in the majority, happy to share their knowledge with you. I will miss this world when I am forced to return to the mundane real world.

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