Mild vs. medical HBOT: what ATA really means
When you shop around for hyperbaric sessions, you'll see words like "mild," "soft-shell," "hard-shell" and numbers like 1.3 or 2.4 ATA. Here's what they mean.
ATA, briefly
ATA stands for atmospheres absolute. At sea level, the air around you is at 1.0 ATA. At 2.0 ATA, the pressure is double, about what a diver feels at 33 feet of seawater.
Mild HBOT (around 1.3–1.5 ATA)
"Mild" HBOT usually means a soft-shell chamber: a zip-up, inflatable fabric chamber pressurized to roughly 1.3 ATA, sometimes up to 1.5.
- Soft chambers are FDA-cleared for treating acute mountain sickness, which is why they're portable.
- Many deliver concentrated oxygen through a mask from an oxygen concentrator, not pure medical oxygen.
- They tend to be the least expensive option per session.
Hard-shell chambers (often 1.5–2.0+ ATA)
Hard-shell chambers are rigid steel or acrylic vessels. Depending on the model, they can safely reach higher pressures. Some are seated; others you lie down in.
Medical HBOT (typically 2.0–3.0 ATA)
Hospitals and wound centers treat medical conditions at roughly 2.0 to 3.0 ATA, with 100% medical oxygen, under physician supervision. These are the pressures used in the research behind the FDA-cleared uses. Higher-pressure sessions generally require a prescription.
Which is "better"?
It depends on why you're going.
- For a medical condition on the recognized list, you need a medical program at the pressure your doctor prescribes. A mild chamber is not a substitute.
- For wellness and relaxation, lower-pressure sessions are a common choice. Be aware that the strong research evidence for HBOT comes from medical pressures, and results from medical studies can't simply be assumed to apply at 1.3 ATA.
Questions to ask any provider
- What pressure (ATA) does your chamber reach?
- Is it soft-shell or hard-shell?
- Do I breathe 100% oxygen, or concentrated oxygen from a concentrator?
- Who is on site during my session, and what training do they have?
- Do you screen for health conditions before the first session?
A good provider will answer all of these clearly. See also Your first HBOT session: what to expect.