The ability of the Vascular Neck Restraint/Carotid Restraint Control Hold to cause temporary and brief syncope (unconsciousness) stems from a combination of factors which occur when bilateral compression is placed along the sides of the neck. Compressed carotid arteries result in diminished cerebral cortex circulation due to inadequate blood flow. This transient loss off blood flow quickly renders the cerebral cortex temporarily unable to maintain an "awake state." Once compression is released, adequate blood flow rapidly returns and the individual quickly recovers. Because the carotid arteries only supply about 3/4 of the blood to the brain, the brain is not totally deprived of blood flow during bilateral compression​. The vertebral arteries supply the remaining 1/4 of oxygenated blood and are capable of maintaining the vital functions of the mid-brain during temporary bilateral compression. Due to their location within the vertebrae, the vertebral arteries are protected and are not directly affected by bilateral compression. 

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In addition to carotid artery compression, the jugular veins which run parallel to the carotid arteries are also compressed during the hold. The jugular veins are more significantly compressed due to their weaker wall structure and the fact that they operate at a much lower pressure than the carotid arteries. The compression of the jugular veins reduce blood flow away from the brain causing vascular congestion. This is evident during most holds as the person's face can become flush and the veins at the neck, forehead and temple become more distended due to the back up of pressure. This congestion impairs cerebral circulation and reduces blood oxygen saturation which may also contribute to syncope.

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​​Although the primary mechanism of syncope is decreased cerebral blood flow due to bilateral carotid compression, the vagus nerve may also play a minor role in syncope in some individuals. The vagus nerve is located along the sides of the neck with the carotid arteries and jugular veins. The carotid sinus is located near the bifurcation of the internal and external carotid artery on the sides of the neck. The carotid sinus contains baroreceptors which connect with the vagus nerve. These baroreceptors detect and measure blood pressure and send signals through the vagus and glossopharyngeal nerves to the cardio regulatory and vasomotor centers in the medulla oblongata. Bilateral compression of the neck or vascular congestion may increase the baroreceptor signal rate to the medulla oblongata resulting in a parasympathetic response to the heart and vascular system. This parasympathic response can reduce blood pressure, stroke volume and heart rate (bradycardia). A recent neck restraint study involving volunteers indicates that blood pressure, heart rate, and heart function are not as adversely affected as previously suggested during or immediately following bilateral vascular restraint application. These baroreceptors were not stimulated to an important physiological degree and are not likely to independently cause syncope due to compression.

 

Proper application of a Vascular Neck Restraint/Carotid Restraint Control Hold by a trained officer can result in rapid and brief unconsciousness. This provides law enforcement officers the opportunity to safely control and apply restraints on dangerous individuals who are not responsive to standard arrest and control methods, or less-lethal devices. For more information on vascular neck restraint physiology, please click articles and studies below.