What Actually Happens in a Hyperbaric Oxygen Session?

If you've heard about hyperbaric oxygen therapy and you're curious but a little uncertain, you're not alone. Most people picture something out of a hospital — sterile, clinical, slightly intimidating. The reality is much closer to a really good nap. Here's exactly what to expect, step by step.

Hyperbaric oxygen therapy — HBOT for short — is one of those treatments that sounds more dramatic than it actually is. The word "chamber" doesn't help. Neither does the medical-grade version that hospitals use, which is a serious procedure for serious wounds. The kind we offer at Asclepius is called mild hyperbaric oxygen therapy, or mHBOT, and it's a much gentler relative. Lower pressures, shorter sessions, no scary side effects, and no prescription required.

That said, "what's it like in there?" is the most common question we hear from new clients. So let's walk through it.

Before You Arrive

You don't need to do much to prepare. A few practical notes, though, that will make your first session smoother:

Wear soft, comfortable clothing. Sweats, leggings, a t-shirt — anything you'd wear to lounge. The chamber is warm and you'll be lying down. You don't need to change.

Eat a light meal an hour or two before. Not strictly required, but you'll be more comfortable. A full stomach or a totally empty one can both make the session less pleasant. Aim for somewhere in between.

Hydrate. Cells use oxygen better when you're well-hydrated. A glass of water on the way in is plenty.

Bring something to do. Most people just close their eyes. Some bring a book or download a podcast on their phone. The chamber has soft lighting and a window, so reading is fine. Just make sure your device is fully charged — you can't bring chargers in.

One thing to skip: don't wear cologne, perfume, or scented lotions. The enclosed environment magnifies smells, and what's pleasant in an open room can become a lot in there. Same with hairspray.

Arriving and Settling In

You'll come in, check in at the front desk with Alexis or whoever's at the counter, and one of our technicians — usually Tom — will walk you back to the chamber room. The chamber itself is a softshell unit about the size of a one-person tent, lying horizontally on a low platform. There's a mattress, a pillow, and a clear viewing window along the side.

Tom will run through a quick safety briefing. Nothing alarming — he'll point out the zipper, show you how the intercom works, and explain how to signal if you want to come out early. You'll never be locked in. The chamber pressurizes from the inside, and you control the exit.

"Most people are nervous for about three minutes. Then they realize the chamber is basically a very fancy nap pod."

You'll lie down inside, settle in with your phone or book, and Tom will zip the chamber closed.

Pressurization — The First Few Minutes

This is the part new clients ask the most about, because it's the part that feels like something. As the chamber pressurizes, the air gets denser. The pressure goes up gradually — not suddenly — over about 8 to 10 minutes. You'll hear a soft hiss as oxygen-enriched air flows in.

The sensation in your ears is similar to taking off in an airplane. There's a mild fullness, and you'll need to "pop" your ears the same way you would on a flight. The standard tricks all work:

• Swallow.
• Yawn.
• Pinch your nose, close your mouth, and gently blow against the closed nostrils (the Valsalva maneuver).

If your ears struggle to clear — say, you're a little congested — let the technician know over the intercom and they'll slow the pressurization rate. You're never on a fixed timer. The chamber adjusts to you, not the other way around.

The Session Itself — 60 Minutes of Doing Almost Nothing

Once the chamber is fully pressurized, the session begins. From the inside, it feels remarkably uneventful — and that's the point. You're lying still, breathing the oxygen-rich air, and the chamber maintains the pressure for the entire session.

Here's what's happening that you won't feel. Under the increased pressure, more oxygen dissolves directly into your blood plasma — not just bound to red blood cells, but freely dissolved in the liquid portion of your blood. That dissolved oxygen reaches tissues and capillaries that would normally be hypoxic, including areas of injury or inflammation. Your body uses this surplus oxygen to support repair, reduce swelling, fight off infection, and produce more cellular energy.

Phase	Duration	What You Feel
Briefing & settle-in	~5 min	A little anticipation. That's it.
Pressurization	8–10 min	Mild ear pressure, like a flight takeoff.
Treatment time	60 min	Calm. Some people sleep. Most don't.
Depressurization	5–8 min	Ears clearing in the other direction.

What clients report most often during the session: a kind of weighted calm. Some fall asleep. Most don't, but their brain slows down. The drone of the chamber is gentle and white-noise-like, the lighting is soft, and there's nothing to do. For people whose lives are full of inputs, that's often the best part.

Coming Out

At the 60-minute mark, the chamber begins depressurizing. This part takes about 5 to 8 minutes. The pressure drops gradually, and your ears clear in the other direction — usually a bit easier than they cleared on the way in. Tom will check in over the intercom to make sure everything feels okay.

When the pressure has fully equalized, the zipper opens, and you climb out. You'll feel a little disoriented for the first minute — partly from lying down for an hour, partly from the slight oxygen redistribution. Stand up slowly, drink some water (we have it on hand), and take a beat.

Most people leave the room with a noticeable shift. The most common descriptions:

• Mental clarity. Like the brain fog has lifted by a few notches.
• Calm energy. Not buzzy. More like the post-good-sleep version of awake.
• Reduced soreness. Especially noticeable the day after, more than immediately.

About one in ten people feels nothing dramatic on the first session. That's normal. The benefits compound across multiple sessions, especially when you're using HBOT for a specific recovery or wellness goal.

What to Do Right After

For the rest of the day, our standard guidance is:

Stay hydrated. Your tissues just took on a lot of oxygen, and they'll work better if they have water to work with.

Don't go straight into a heavy workout. A walk, a light bike ride, or yoga is fine. Heavy lifting or sprint work right after can blunt the benefits — give it a few hours.

Eat something with protein. Recovery happens with raw materials. Even a simple meal with quality protein helps your body capitalize on the session.

If you're stacking — and we hope you are — schedule the next modality thoughtfully. HBOT pairs especially well with red light therapy and IV nutrition. We covered the order in our stacking article if you want the full breakdown.

The Honest Bottom Line

If you've been on the fence about HBOT because you weren't sure what to expect, here's the short version: it's calmer than you think, easier than you'd guess, and the most "medical-feeling" part of the whole thing is a little ear pressure for ten minutes. The other 60 minutes is just you, lying down, breathing.

The benefits build across multiple sessions, but most people feel something after the first one. If you're curious whether HBOT might fit what you're working on — recovery, sleep, focus, post-illness — the easiest move is a free 30-minute consultation. Walk in or call us. We'll talk it through, no commitment needed.