Hyperbaric Oxygen (HBOT) for POTS: Does It Help?

What Does Hyperbaric Oxygen Therapy Do?

Hyperbaric oxygen therapy means breathing 100% oxygen inside a chamber pressurized above normal air pressure, which is 1 atmosphere absolute (ATA). A review's abstract reports that this raises the share of oxygen dissolved in the blood 5 to 20 times (Schottlender, 2021). A second review describes the result as hyperoxia, an oxygen level above normal, and proposes that repeated sessions are sensed by cells as a relative shortage of oxygen, which switches on the HIF-1α pathway (Cannellotto, 2024). That second idea is a proposed mechanism.

The trials covered below used about 1.5 to 2.4 ATA, sessions of 60 to 90 minutes where reported, and courses of 10 to 40 sessions (Boussi-Gross, 2013; Harch, 2020; Zilberman-Itskovich, 2022; Kjellberg, 2025).

Why Does Brain Blood Flow Matter for HBOT?

Oxygen gets to the brain only as fast as blood carries it there, and in POTS, standing is when that delivery comes under strain. A single-center retrospective study compared 16 people with POTS, 16 with hypocapnic cerebral hypoperfusion and 16 controls. Brain blood flow velocity fell more on standing in both patient groups than in the controls, exhaled CO2 ran lower, and the authors tied the drop to the vessel-narrowing effect of low CO2 (Novak, 2018).

Other work points the same way. In 11 people with suspected POTS who became short of breath on a tilt table, the abstract reports that brain blood flow velocity fell before the over-breathing began (Del Pozzi, 2014). The abstract of a single lab's study reports that 50% of people with POTS become hypocapnic, meaning low in CO2, on standing, tied to a brief blood pressure drop at the start (Stewart, 2023).

High oxygen also acts on brain vessels directly. In 7 healthy men breathing 100% oxygen at normal air pressure, brain blood flow measured by MRI was 28.7 to 32.6% lower than on room air, and the analysis tied that to the oxygen level itself, apart from CO2 (Floyd, 2003). The abstract of a 2026 study in 15 young adults, with CO2 held steady, reports "widespread cerebral vasoconstriction" from high oxygen (Khademi Motlagh, 2026). In rats at 5 ATA, far above the pressures used in people, regional brain blood flow fell 23 to 37% (Demchenko, 2000).

Brain blood flow has been measured during HBOT. In 8 healthy volunteers breathing oxygen at 2 ATA, inside the range of the trials covered below, blood flow velocity in a main brain artery fell compared with room air at normal pressure, and the pressure itself made no difference (Omae, 1998). In 23 subjects breathing oxygen at 2.8 bar, the fall was larger than the change in exhaled CO2 explained (Visser, 1996).

Other studies point the other way over time. The long COVID trial covered below reported more brain perfusion on MRI 1 to 3 weeks after its 40-session course (Zilberman-Itskovich, 2022), and in severe brain injury, HBOT at 1.5 ATA raised brain blood flow and the brain's oxygen use for 6 hours after treatment (Rockswold, 2010). Those measurements were taken after treatment, and none were in POTS.

Those findings lead to our team's hypothesis. HBOT sessions happen sitting or lying down, when brain blood flow in POTS is closest to normal. In our team's view, that's HBOT's ceiling for POTS: the extra oxygen arrives while you're lying down, and a session doesn't change what brain blood flow does when you stand up afterward. Our team found no study that tested this in POTS, so it stays a hypothesis. The video compares it to boats full of supplies on a river that's been dammed.

Room air Chamber Standing later

Replay

What Do HBOT Trials Show?

Our team found no trial of HBOT in POTS. The nearest autonomic study is a retrospective review of 92 intensive care patients with paroxysmal sympathetic hyperactivity, surges of heart rate, blood pressure and sweating after severe brain injury. Those given HBOT had lower symptom scores and shorter intensive care stays than 36 patients treated without it (Wang, 2025), and that group's problem and setting are far from POTS. The closest mention in POTS is a 2024 review of long COVID brain fog and POTS. It describes "marginal benefits" from HBOT for post-COVID brain fog and points to established POTS therapies that improve blood return to the heart and lower the heart rate for long COVID POTS (Tavee, 2024). When brain fog is the main complaint, why brain fog gets worse when you stand covers the upright side of it.

The 2 sham-controlled long COVID trials asked different questions and got different answers. In a double-blind trial of 73 people with long COVID, 40 daily sessions improved global cognitive function, attention and executive function compared with sham (p between 0.038 and 0.05), the abstract reports (Zilberman-Itskovich, 2022). A follow-up of 31 people from that trial, run by the same research group with no control group, reports that the gains persisted (Hadanny, 2024). A double-blind Swedish trial of 79 people gave 10 sessions at 2.4 bar and found no difference from placebo in physical function or physical role limits, and both groups improved (Kjellberg, 2025). Systematic reviews that pooled small trials and observational studies reported some benefit and call for larger randomized trials (Wu, 2024; Zamora, 2025).

The post-concussion evidence is disputed. 2 crossover trials, 1 with 63 people randomized and 1 with 56, each gave 40 sessions and reported gains in symptoms or cognition compared with a period of no treatment (Harch, 2020; Boussi-Gross, 2013). A 2015 editorial on earlier post-concussion HBOT trials listed sham groups breathing room air at raised pressure, delayed treatment, subjective outcomes and small samples as problems (Hu, 2015). The 2 trials above used no-treatment control periods rather than placebo. Our team's approach to lasting concussion symptoms is on the post-concussion treatment page.

Who Might HBOT Hurt?

In a retrospective review of 2,334 patients treated for a mix of conditions at 1 center in Israel, the same center that ran the long COVID trial above, 17.4% had at least 1 adverse event, a rate of 0.72% per session. Middle ear barotrauma, an ear injury from the pressure change, occurred in 9.2% of patients and 0.04% of sessions, with a higher risk in women and children under 16. Low blood sugar, oxygen toxicity, dizziness, anxiety reactions, shortness of breath and chest pain occurred in 0.5 to 1.5% of patients (Hadanny, 2016).

A narrative review of the field puts middle ear barotrauma lower, at up to 2% of treated patients, and names claustrophobia among the most common problems. It adds short-sightedness that's usually temporary and reverses after sessions stop. It says seizures from oxygen are rare, happen at higher oxygen pressures and often occur during emergency treatment of acidotic patients such as carbon monoxide poisoning (Camporesi, 2014). None of these figures come from people with POTS.

The Swedish long COVID trial excluded people with diabetes, high blood pressure or other reasons not to have HBOT, and it reported adverse events in 49% of the HBOT group and 44% of the placebo group, with 1 serious event in the HBOT group and 1 death in the placebo group (Kjellberg, 2025). In our team's view, the risk for someone with POTS is starting a long course of sessions before anyone has measured what their brain blood flow does when they stand.

Where Does HBOT Fit in POTS Care?

Our team's view is to map the upright blood flow problem first: what heart rate, blood pressure, breathing and CO2, and where available brain blood flow, do as you go from lying down to standing. The tilt table test guide covers how that testing works. The basics that affect delivery, such as blood volume, posture and breathing, come next. If HBOT is considered after that, our team's view is that it should be for a clear reason.

HBOT is a prescribed therapy delivered at a hyperbaric provider, and the upright delivery problem is what our team works on.

If you've already done a course of HBOT and your symptoms still flare when you stand, that fits our team's hypothesis above, though it doesn't prove it. Measuring what your brain blood flow does on standing is the next step.

Hyperbaric Oxygen and POTS: FAQ