Clinical trials have suggested that this device is effective in mitigating changes in brain structure and function in athlete populations. The purpose of the current study is to measure the response of the jugular vein to various pressures applied by a generic compression device across various ages and gender. The relative jugular vein response will be measured using ultrasound.

The Device has the promise of providing a novel mechanism for reducing or preventing the likelihood of TBI, and may be used in conjunction with other protective equipment. TBI is the leading cause of death in individuals under age 45. The cost of TBI in the U.S. is estimated at anywhere from $50 to $150 billion, annually. Concussion in female high school soccer players have been noted to occur at a rate of 4.5 concussions per 10,000 athletic exposures (Comstock, Currie et al. 2015). The investigators propose that Slosh Theory can explain these differences offering a mechanistic approach that could help shed light on further ways to alleviate the TBI burden on society. Note that Slosh Theory teaches that hydrodynamics (fluids moving within moving containers) contribute to, or are even the main etiology for, energy absorption of the cranial contents and that mitigation of SLOSH (increased compensatory reserve volume) may mitigate TBI. Significant morbidity, mortality, and related costs are caused by traumatic brain injury (TBI). A simple, effective, and lightweight device worn by athletes or war fighters in the field, designed to mitigate TBI resulting from blast trauma or concussive events, would save lives, and the huge costs currently being experienced for life-treatment of surviving victims. An externally-worn medical device (the Device) that applies mild jugular vein compression according to the principle of the Queckenstedt Maneuver, is being developed by Q30 Sports Science, LLC (Q30). Preliminary research suggests that the Device has the potential to reduce the likelihood of TBI. The currently developed collar (Smith 2009, Smith and Fisher 2011, Smith and Fisher 2011, Smith 2012) has been approved for studies in humans (IRB 2013-2240) and the results indicate safety for use during high demand and maximal exertion activities. Regarding safety, the externally worn collar is meticulously designed to mimic the body's own omohyoid muscle actions upon the jugular veins that will provide similar pressure and volume increases not to surpass that of a yawn or the mere act of just lying down. Initial safety testing and early clinical trials indicate that the collar application is both safe and efficacious to prevent brain microstructure and neurophysiological changes in response to head impacts.

Inclusion Criteria:

• Normal healthy volunteer aged 7-60
• Able to provide written consent
• Able to tolerate hypercapnia for 1-2 minutes

Exclusion Criteria:

• Unable to provide written consent
• History of neurological deficits, previous cerebral infarction, or severe head trauma as indicated through pre-season screening:
• Medical contraindications to restriction of venous outflow via the internal jugular veins (known increased intracerebral pressure, metabolic acidosis or alkalosis)
• Glaucoma (Narrow Angle or Normal Tension)
• Hydrocephalus
• Recent penetrating brain trauma (within 6 months)
• Known carotid hypersensitivity
• Known increased intracranial pressure
• Central vein thrombosis
• Any known airway obstruction
• Any known seizure disorder

3 days