Beyond Oxygen: How CO₂ Regulation Affects Fatigue and Pain in hEDS and Neurodivergence

Carbon dioxide (CO₂) is one of the most misunderstood parts of human physiology.

Most of us grow up learning that CO₂ is something the body needs to get rid of, a waste gas, the opposite of oxygen, a sign of poor air quality or danger. We’re encouraged to take deep breaths, breathe more, and “get more oxygen in,” rarely stopping to ask what happens to CO₂ in the process.

Almost no one asks: What if my CO₂ is too low?

Not because it isn’t relevant, but because we’re never taught that low CO₂ can matter at all.

In hypermobile and neurodivergent communities, this question tends to appear indirectly. Someone mentions it in a video. A physiotherapist brings it up in passing. A client notices their symptoms worsen when they breathe more, not less. Slowly, a pattern emerges.

At ParaMotion, we don’t approach this as a new diagnosis or a hidden condition. We approach it as something much more practical:

CO₂ is a signal. A reflection of how breathing mechanics, posture, and nervous system regulation are interacting in the body.

Understanding that signal can change how we think about fatigue, pain, dizziness, and movement tolerance, especially in hypermobile and neurodivergent bodies.

First: low CO₂ Is Not a Condition

Let’s clear this up early.

Low carbon dioxide in the blood is sometimes called hypocapnia. That term exists, but it often causes confusion. It makes low CO₂ sound like a disease someone has, rather than a state the body moves in and out of depending on how it’s regulated.

In the context of hypermobility and neurodivergence:

• Low CO₂ is not a diagnosis

• It is not a standalone illness

• It is not something that randomly goes wrong

Instead, it is a predictable physiological outcome of how ventilation is organized.

To understand why, we need to talk about what CO₂ actually does.

What CO₂ Does (That Oxygen Can’t Do Alone)

Breathing is not just about oxygen.

Oxygen availability matters, but oxygen delivery matters more. And CO₂ plays a key role in that delivery.

1. CO₂ helps oxygen leave the blood

Oxygen binds to hemoglobin in the blood. Whether it stays bound or gets released into tissues depends partly on CO₂ levels, a well-established principle in physiology known as the Bohr effect.

When CO₂ is lower:

• Oxygen binds more tightly to hemoglobin

• Less oxygen is released into muscles, organs, and the brain

This means someone can have:

• Normal oxygen saturation

• Healthy lungs

• And still experience tissue-level oxygen shortage

This is one reason fatigue and brain fog can exist without obvious abnormalities on standard tests.

2. CO₂ stabilizes nerve and muscle function

CO₂ helps regulate blood pH. When CO₂ drops, the blood becomes slightly more alkaline.

This shift increases:

• Nerve excitability

• Muscle tension

• Sensory sensitivity

Which can show up as pain amplification, twitching, headaches, or feeling “wired but tired.”

3. CO₂ supports blood flow to the brain

CO₂ helps keep cerebral blood vessels appropriately dilated. When CO₂ drops, those vessels constrict.

Reduced cerebral blood flow can contribute to:

• Dizziness or lightheadedness

• Visual disturbances

• Cognitive fatigue

This becomes especially relevant during standing, movement, or prolonged effort.

So Why Would CO₂ Run Low in the First Place?

Here is the most important reframing:

CO₂ levels are determined by ventilation, not oxygen.

Ventilation simply means how much air moves in and out of the lungs relative to the body’s needs.

And ventilation is shaped by three things:

1. Breathing mechanics

2. Posture and muscle tone

3. Nervous system regulation

All three are commonly different in hypermobile and neurodivergent bodies.

Why Lower CO₂ Is a Predictable Outcome in hEDS and Neurodivergence

1. Hypermobile mechanics change breathing efficiency

In hypermobile Ehlers-Danlos syndrome and related conditions:

• The rib cage is often more mobile

• The diaphragm may lack stable anchoring

• Abdominal and core tone are frequently reduced

Breathing still works, but it often becomes less mechanically efficient. To compensate, the body subtly increases breathing volume or frequency.

This doesn’t feel dramatic.It doesn’t look like panic.It just means more air moves than is strictly necessary.

And increased ventilation naturally lowers CO₂.

No disease required.

2. The nervous system sets a higher breathing baseline

Breathing is largely automatic. It’s regulated by brainstem centers responding primarily to CO₂ levels.

In many people with hEDS, POTS or orthostatic intolerance, or autism or ADHD, the nervous system operates closer to a sympathetic (alert) baseline.

This slightly elevated arousal:

• raises breathing drive

• increases ventilation at rest

• lowers CO₂ over time

Again, this is not pathology, it’s regulation.

3. Effort, posture, and cognition amplify the effect

Standing upright, stabilizing joints, managing sensory input, or concentrating all increase demand on the system.

In bodies that already ventilate a bit more than necessary:

• posture changes

• movement

• cognitive load

…can push CO₂ lower, which helps explain why symptoms often worsen with standing, activity, or prolonged focus — not only with intense exercise.

The key point

Low CO₂ in these populations is not mysterious, rare, or trendy.

It is the expected downstream effect of how the system is organized.

What This Can Feel Like in Real Life

Because CO₂ affects multiple systems at once, its effects are often diffuse rather than obvious.

People may experience:

• Brain fog or slowed thinking

• Lightheadedness, especially when upright

• A sense of air hunger despite breathing frequently

• Muscle tension, burning, or widespread pain

• Palpitations or shakiness

• Fatigue that doesn’t resolve with rest

• Normal oxygen readings but persistent symptoms

Low CO₂ rarely acts alone, but it can amplify pain, fatigue, and autonomic instability already present in hypermobile and neurodivergent bodies.

How CO₂ Is Looked At Clinically

This is where expectations matter.

CO₂ is not routinely assessed, and standard oxygen tests do not reflect it.

Ways CO₂ may be evaluated include:

• End-tidal CO₂ (EtCO₂) via capnography, which reflects breathing patterns in real time

• Arterial or venous blood gas testing, typically in hospital settings

• Indirect markers like bicarbonate levels, which offer limited context

CO₂ levels can change with posture, effort, stress, and fatigue, which is why static testing often misses relevant patterns in hypermobility and dysautonomia.

Can I tell at home if my CO₂ is low?

There is no reliable self-test that can tell you whether your CO₂ is “low” in a medical sense.

But there are a few gentle self-observations that can give you a rough sense of how your breathing system is behaving, if they’re framed correctly and not overinterpreted.

Here are non-invasive, non-diagnostic clues that breathing regulation might be inefficient:

Breathing-related patterns

• Frequent sighing or yawning

• Mouth breathing at rest

• Breathing that feels “busy” even when still

• Difficulty breathing slowly without discomfort

Body-level patterns

• Symptoms worsen with standing, talking, or concentrating

• Exercise feels disproportionately exhausting

• Fatigue or dizziness appears before muscles feel worked

• Relief when lying down or supported

Nervous system cues

• Strong urge to control the breath

• Breath-holding during effort or focus

• Feeling worse when “taking deep breaths”

None of these prove low CO₂, but together, they suggest ventilation may be mismatched to need.

Why This Matters for Movement and Therapy

From a movement and rehabilitation perspective, this matters deeply.

When ventilation is inefficient and CO₂ is low:

• Muscles fatigue faster

• Stabilization work feels disproportionately exhausting

• Exercise tolerance drops

• Post-exertional symptom flares are more likely

• The nervous system shifts toward threat rather than safety

This is why breathing work in hypermobile bodies must be:

• gentle

• coordinated

• regulation-focused

Not about forcing breath control or “training” gases.

Support, Not Control

Supporting CO₂ balance is not about fixing a number.

It’s about:

• improving breathing efficiency

• restoring mechanical support

• reducing unnecessary ventilation

• helping the nervous system feel safe enough to settle

Helpful approaches may include:

• breathing pattern education

• postural and rib cage support

• paced, regulation-informed movement

• nervous system–aware therapy

What doesn’t help:

• aggressive breath holding

• rebreathing into bags

• treating CO₂ as a cure or target

A Note on Immediate Sensations & Patience

When beginning to address breathing patterns, it’s common to feel temporarily more aware of air hunger or slight anxiety. This isn't a step backward. It's the nervous system noticing a change in a familiar, if inefficient, habit. Progress is measured in weeks by a gradual decrease in baseline symptoms (less fog, more stability), not in minutes by the absence of discomfort. Consistency with gentle practice trumps intensity.

The Takeaway

Carbon dioxide is not something to fear or chase.

For many people with hypermobile EDS and neurodivergence, it is a quiet but meaningful indicator of how the system is coping with the demands placed on it.

Understanding CO₂ helps us shift the question from:

“What’s wrong with my body?”

to:

“How is my body trying to adapt, and how can I support it better?”

That shift is at the heart of what we do at ParaMotion: education that leads to kinder, more sustainable movement, grounded in real physiology.

Resources and further reading

• Impairment of lung volume perception and breathing control in hypermobile Ehlers-Danlos syndrome

• Evaluation and Management of Dyspnea in Hypermobile Ehlers-Danlos Syndrome and Generalized Hypermobility Spectrum Disorder: Protocol for a Pilot and Feasibility Randomized Controlled Trial

• Hypermobile Ehlers-Danlos Syndrome: Cerebrovascular, Autonomic and Neuropathic Features

• Postural Hyperventilation as a Cause of Postural Tachycardia Syndrome: Increased Systemic Vascular Resistance and Decreased Cardiac Output When Upright in All Postural Tachycardia Syndrome Variants