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Old 01-08-2012, 05:09 PM   #57
CitoMaramba
 
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Dojo: Dangayan Singkaw Aikido Shinzui Group Philippines
Location: Plymouth, UK
Join Date: Nov 2003
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Re: Why don't we practice chokes?

Here is the abstract of a very recent (published November 2011) study on the cause of loss of consciousness during Vascular Neck Restraint. I have highlighted the main conclusions of the study.
http://www.ncbi.nlm.nih.gov/pubmed/22096121
Quote:
J Appl Physiol. 2011 Nov 17. [Epub ahead of print]
Mechanism of Loss of Consciousness during Vascular Neck Restraint.
Mitchell JR, Roach DE, Tyberg JV, Belenkie I, Sheldon RS.
Source

1University of Calgary.
Abstract

Vascular neck restraint (VNR) is a technique that police officers may employ to control combative individuals. As the mechanism of unconsciousness is not completely understood, we tested the hypothesis that VNR simply compresses the carotid arteries thereby decreasing middle cerebral artery blood flow. Twenty-four healthy police officers (age 354 years) were studied. Heart rate (HR), arterial pressure, rate of change of pressure (dP/dt) and stroke volume (SV) were measured using infrared finger photoplethysmography. Bilateral mean middle cerebral artery flow velocity (MCAVmean) was measured using transcranial Doppler ultrasound. Neck pressure was measured using flat, fluid-filled balloon transducers positioned over both carotid bifurcations. To detect ocular fixation, subjects were asked to focus on a pen that was moved from side to side. VNR was released 1-2 sec after ocular fixation. Ocular fixation occurred in 16 subjects (time 9.50.4 [SEM] sec). Pressures over the R and L carotid arteries were 25722 and 146 18 mmHg, respectively. VNR decreased MCAVmean (R 453 to 84 cm/s; L 532 to 103 cm/s) and SV (924 to 754 ml) (P < 0.001). Mean arterial pressure (MAP), dP/dt and HR did not change significantly. We conclude that the most important mechanism in loss of consciousness was decreased cerebral blood flow caused by carotid artery compression. The small decrease in CO (9.6 to 7.5 L/min) observed would not seem to be important as there was no change in MAP. In addition, with no significant change in HR, ventricular contractility or MAP, the carotid sinus baroreceptor reflex appears to contribute little to the response to VNR.

PMID:
22096121
[PubMed - as supplied by publisher]

Inocencio Maramba, MD, MSc
Dangayan Singkaw Aikido Shinzui
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