A method is provided for reducing the risk of sustaining a traumatic brain injury caused by a traumatic event that includes identifying a subject at risk of sustaining a traumatic brain injury, and then precisely increasing the partial pressure of carbon-dioxide (CO2) in the blood of the subject (pCO2). This method can be applied to raise the CO2 and pCO2 to improve orthostatic hypotension in conditions such as dysautonomias (like Positional Orthostatic Tachycardic Syndrome POTS) and to facilitate the drive to breathe in conditions like Central Sleep Apnea (CSA) and Sudden Infant Death Syndrome (SIDS). The pCO2 of the person is increased by placing a breathing apparatus over the mouth of the person through which the person must breath, wherein the breathing apparatus includes an enlarged dead space volume in which expired CO2 collects to be inhaled or re-breathed by the person on the next inhalation.
