In VA Study, CO2 Therapy Shows Promise for Veterans With Parkinson’s Disease

When Vietnam-era veterans develop Parkinson’s disease, the Department of Veterans Affairs attributes it to Agent Orange exposure. Now, thanks to new VA-funded research, they and other veterans who face elevated risks of neurodegenerative diseases could have a clue to a future treatment — one that doesn’t involve drugs.

Your brain has a waste disposal system. It works best when you’re in deep sleep, pumping cerebrospinal fluid through brain tissue to carry away toxic proteins that build up during the day. When that system breaks down, those proteins accumulate. In Parkinson’s disease, clumps of a misfolded protein called alpha-synuclein build up in brain cells and destroy them. In Alzheimer’s, it is amyloid-beta and tau. The waste clearance system, called the glymphatic pathway, is supposed to prevent that. In people with Parkinson’s, it often does not work well enough, in part because the disease disrupts the deep sleep the system depends on.

Now, a team of researchers funded by the New Mexico VA Health Care System, the University of New Mexico School of Medicine and the Mind Research Network has found a way to turn that system on while patients are wide awake, using nothing more than carefully timed pulses of carbon dioxide.

How It Works

The research, published in NPJ Parkinson’s Disease, was led by neuropsychologist Dr. Sephira Ryman, an assistant professor at UNM’s Department of Neurology who treats patients at UNM’s Movement Disorder Center. In earlier work, Ryman found that Parkinson’s patients have a reduced and delayed cerebrovascular response to changes in CO2. Their blood vessels do not expand and contract as readily as those of healthy adults, which blunts the pumping action that drives cerebrospinal fluid through the brain.

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The insight was that during deep sleep, slow breathing naturally raises and lowers CO2 levels, causing blood vessels in the brain to rhythmically dilate and constrict. That mechanical pulsing pushes cerebrospinal fluid through the glymphatic pathway. If Parkinson’s patients cannot reach or sustain deep sleep, the system never fully activates. Ryman’s team asked: What if we reproduce that CO2 rhythm artificially while the patient is awake?

In one experiment, 63 older adults, 30 of whom had Parkinson’s, underwent MRI brain imaging while breathing air with slightly elevated CO2 for about 35 seconds at a time, alternating with normal air. In both healthy participants and those with Parkinson’s, the rhythmic CO2 pulses changed how cerebrospinal fluid moved through the brain, indicating that the glymphatic system had been stimulated.

In a second experiment, 10 participants, five with Parkinson’s, underwent three 10-minute sessions of the CO2 treatment. Blood samples were drawn at approximately 45, 90 and 150 minutes afterward. Both groups showed increased levels of waste proteins in their blood, including proteins associated with Parkinson’s and Alzheimer’s disease. The waste had been flushed from the brain into the bloodstream, where other organs can filter it out.

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What makes this research distinctive is that it points toward a non-drug intervention. Every current Parkinson’s treatment focuses on managing symptoms, primarily by supplementing dopamine. The new approach targets the physical maintenance of the brain itself: keeping the waste disposal system running so toxic proteins do not accumulate in the first place. If it works at scale, it would represent a shift from symptom management to disease modification.

What Comes Next

The research is early-stage. The sample sizes are small, and it remains unclear whether improved waste clearance actually slowed Parkinson’s progression or just moved proteins around. Ryman’s team is now investigating whether breath-centered practices such as yoga, tai chi and qigong, which emphasize slow abdominal breathing and naturally raise CO2 levels, can produce a similar effect without specialized gas delivery equipment. A second paper accepted for publication in the Journal of Cerebral Blood Flow and Metabolism describes that line of inquiry.

Ryman cautioned that deliberately altering breathing patterns can affect blood pressure, heart rate and oxygenation, and that no one should attempt to replicate the CO2 protocol without medical supervision. But the underlying idea is striking in its simplicity: The brain already knows how to clean itself. The question is whether we can help it do that job better, especially in the people whose brains need it most.

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