What to Expect at Your First Hyperbaric Oxygen Therapy Session

You're booked for your first hyperbaric oxygen therapy session, and your mind is racing. Will the chamber feel cramped? Will your ears hurt? What if something goes wrong? These are the exact questions most first-time patients have, and every single one has a straightforward answer.

A typical session lasts 60 to 90 minutes, during which you breathe pure oxygen inside a pressurized chamber at 1.5 to 3.0 times normal atmospheric pressure. The process is painless for most people, and many patients say their first session was far more comfortable than they expected. In this guide, we'll walk you through every step, from what to wear to how it feels, so you can walk into your appointment with confidence.

How to prepare for your first hyperbaric oxygen therapy session

Preparation is simple, but a few details make a real difference in your comfort.

What to wear: Most clinics provide 100% cotton scrubs or gowns for you to change into. Cotton is required because synthetic fabrics can create static electricity in an oxygen-rich environment. Wear comfortable clothes you can easily change out of.

What to eat: Have a light meal or snack within an hour of your appointment. According to Johns Hopkins Medicine, stable blood sugar helps your body respond well during treatment. Avoid heavy, greasy foods that might cause nausea in the chamber.

What NOT to bring: Leave electronics, lighters, matches, and battery-operated devices outside the chamber. Most clinics also ask you to skip perfume, hair spray, deodorant, and petroleum-based lotions before your session. These products can pose a fire risk in a high-oxygen environment.

Medications to discuss: Tell your clinic about all current medications, especially insulin (which may need dosing adjustments) and certain chemotherapy drugs. Your provider will review everything during intake.

David, a 45-year-old runner recovering from a stubborn ankle injury, remembers his pre-session jitters. "I spent more time worrying about what to wear than anything else," he says. "They handed me scrubs, I changed in two minutes, and that was it."

What happens during a treatment session: step by step

Knowing the exact sequence helps eliminate surprises.

Arrival and intake

When you arrive, a trained hyperbaric technician will take your temperature and check your ears with an otoscope. If you have a fever or significant ear congestion, your session may be rescheduled. This is a standard safety step that clinics perform before every treatment.

Entering the chamber

You'll lie on a padded gurney or stretcher that slides into the chamber. In a monoplace chamber (the most common type), you'll be the only person inside a clear acrylic tube. In a multiplace chamber, you'll sit in a room-sized space with other patients and may wear a hood or mask to breathe pure oxygen. Both are safe and effective; you can learn more about the differences in our guide to hyperbaric chamber types.

Pressurization (10 to 15 minutes)

The technician gradually increases the chamber pressure. You'll hear a hissing sound as oxygen flows in, and you may feel warmth as the air compresses. The most noticeable sensation is pressure in your ears, similar to what you feel during airplane descent. We'll cover how to handle this in detail below.

Treatment at pressure (45 to 60 minutes)

Once the chamber reaches the prescribed pressure, typically 2.0 to 2.4 ATA for FDA-approved conditions, you simply relax and breathe normally. Many clinics let you watch TV, listen to music, or nap. A technician monitors you through a window or intercom the entire time.

Depressurization (10 to 15 minutes)

The pressure is slowly reduced back to normal. You may notice mild ear popping again, but it's usually less noticeable than during pressurization. Once the chamber returns to normal pressure, the session is complete.

After the session

You can return to normal activities immediately. There's no recovery time needed. Many patients report feeling relaxed, mentally sharper, or slightly energized after their session.

What does the treatment feel like?

Most first-time patients are surprised by how uneventful the experience is. Here's what you'll actually notice.

Ear pressure

This is the number one sensation patients report. As pressure increases, you'll feel fullness in your ears, exactly like descending in an airplane. Three simple techniques can relieve it:

1. Swallow repeatedly to open your eustachian tubes
2. Yawn widely to equalize pressure naturally
3. Valsalva maneuver: Pinch your nose, close your mouth, and gently exhale as if blowing up a balloon for five to 10 seconds

Most people master equalization within their first session. If you have persistent difficulty, let your technician know; they can slow or pause pressurization until you're comfortable.

Temperature changes

The chamber warms slightly during pressurization (a basic physics effect of compressing gas) and cools slightly during depressurization. The change is mild, and blankets are usually available.

Claustrophobia concerns

Monoplace chambers are clear tubes about three feet in diameter. If tight spaces make you anxious, tell your clinic in advance. Many facilities offer:

• A tour of the chamber before your session
• Music or video to keep you occupied
• Communication with the technician at any time
• Mild anti-anxiety medication if prescribed by your doctor

Maria, a 38-year-old who sought treatment for chronic migraines, was nervous about claustrophobia. "The tube is see-through, so I could see the whole room," she says. "I put on a movie and honestly forgot where I was after 10 minutes."

How long does each session last?

A single session follows a predictable timeline:

Phase	Duration	What happens
Check-in and intake	10-15 minutes	Temperature, ear check, change clothes
Pressurization	10-15 minutes	Chamber slowly reaches treatment pressure
Treatment at pressure	45-60 minutes	Breathe oxygen, relax
Depressurization	10-15 minutes	Chamber slowly returns to normal
Total visit time	75-105 minutes	Including intake and changing

Plan for about 90 minutes to two hours at the clinic for your first visit, which includes paperwork and orientation. Follow-up sessions typically take 75 to 90 minutes total.

Treatment protocols vary by condition. The Undersea and Hyperbaric Medical Society (UHMS) recognizes 15 indications for HBOT, and most protocols call for 20 to 40 sessions scheduled five days per week. That means a typical treatment course runs four to eight weeks. For wellness and recovery applications, shorter courses of 10 to 20 sessions are common.

If you're curious about how costs break down across a full treatment course, our hyperbaric oxygen therapy cost guide covers pricing by clinic type and condition.

Common side effects during your first session

HBOT has a strong safety profile. A 2023 systematic review and meta-analysis published in Frontiers in Medicine confirmed that most adverse effects are mild and self-limiting.

Here's what you might experience:

Middle ear barotrauma is the most common side effect. Research published in the UHMS journal reviewing 5,962 patients found a barotrauma rate of about 9%, though most cases were mild ear discomfort that resolved with equalization techniques. Ongoing coaching on ear-clearing methods and controlled compression rates significantly reduce this risk.

Temporary vision changes can occur after multiple sessions. Some patients develop mild near-sightedness that typically resolves within six to eight weeks after completing treatment.

Fatigue after a session is normal. Your body is working harder to use the extra oxygen for healing. Stay hydrated and rest if needed.

Sinus pressure may occur if you have congestion. If you're dealing with a cold or sinus infection, call your clinic before your appointment; they may recommend rescheduling.

Serious complications like oxygen toxicity or pneumothorax are extremely rare and almost always preventable with proper screening. For a deeper look at all possible side effects, read our complete guide to hyperbaric oxygen therapy side effects.

Questions to ask your clinic before your first session

Not all hyperbaric facilities are the same. Asking the right questions helps you find a clinic that matches your needs.

1. What type of chamber do you use? Monoplace and multiplace chambers operate differently. Hard-shell chambers reach higher pressures (2.0 to 3.0 ATA) suitable for FDA-approved conditions. Soft-shell chambers typically reach only 1.3 to 1.5 ATA.

2. Is a physician present during treatment? UHMS-accredited facilities require physician oversight. This matters, especially for medical conditions.

3. What pressure will be used for my treatment? The UHMS recommends treatment pressures between 2.0 and 3.0 ATA for FDA-approved indications. Lower pressures may be appropriate for wellness applications.

4. What does the session cost, and do you accept insurance? Costs range from $75 to $400 per session depending on chamber type and location. Insurance typically covers FDA-approved conditions. Read our insurance coverage guide for details.

5. What should I do if I feel uncomfortable during the session? Every reputable clinic will have a clear protocol for communication and emergency procedures.

Ready to find a clinic? Browse hyperbaric oxygen therapy clinics near you to compare chamber types, specializations, and contact information.

Frequently asked questions

Can I bring my phone into the hyperbaric chamber?

No. Electronic devices, including phones, tablets, and smartwatches, are not allowed inside hyperbaric chambers. The oxygen-rich environment creates a fire risk with any potential spark source. Most clinics provide entertainment options like TVs or music systems built into the chamber.

Will I feel claustrophobic during treatment?

Some patients feel initial anxiety, but true claustrophobia reactions are uncommon. Monoplace chambers are made of clear acrylic, so you can see the room around you. You can communicate with your technician at any time. If you have a history of claustrophobia, talk to your clinic beforehand so they can help you feel comfortable.

How soon will I notice results?

Results depend on the condition being treated. Some patients notice improved energy or mental clarity after their first few sessions. For wound healing and other medical conditions, measurable improvement typically appears after 10 to 15 sessions. Full benefits usually emerge after completing the prescribed protocol of 20 to 40 sessions.

Is the treatment painful?

No. The treatment itself is painless. The only discomfort most patients report is temporary ear pressure during pressurization, which is easily managed with swallowing, yawning, or the Valsalva maneuver. If you experience pain at any point, notify your technician immediately; they can adjust the pressurization rate.

Can I eat before my session?

Yes, and it's recommended. Have a light meal or snack within an hour of your session. Avoid carbonated drinks and gas-producing foods, which can cause bloating as pressure changes inside the chamber. Stay hydrated before and after treatment.

Your first session is the hardest one to book

Tom, a 61-year-old recovering from radiation therapy for throat cancer, put off scheduling for three months. "I read everything I could find online and still felt nervous," he says. "After my first session, I wondered why I waited so long. It was easier than getting a dental cleaning."

The anticipation is almost always worse than the experience itself. Once you know what to expect, the process is straightforward: show up, change into scrubs, lie down, breathe, and relax for about an hour. Most patients settle into a comfortable routine by their second or third visit.

If you're considering HBOT for a specific condition, start by talking to your doctor about whether it's right for you. Then find a clinic near you to ask questions, tour the facility, and schedule your first session.

You can also explore the conditions treated with hyperbaric oxygen therapy or review our clinical research section to see what the evidence says about your specific situation.

Sources

1. Johns Hopkins Medicine. "Hyperbaric Oxygen Therapy." hopkinsmedicine.org
2. Cleveland Clinic. "Hyperbaric Oxygen Therapy." my.clevelandclinic.org
3. Mayo Clinic. "Hyperbaric Oxygen Therapy." mayoclinic.org
4. Undersea & Hyperbaric Medical Society. "HBO Indications." uhms.org
5. Heyboer M, et al. "Middle ear barotrauma during hyperbaric oxygen therapy: a review of 5,962 patients." Undersea & Hyperbaric Medicine, 2019. uhms.org
6. Zhang Y, et al. "Adverse effects of hyperbaric oxygen therapy: a systematic review and meta-analysis." Frontiers in Medicine, 2023. frontiersin.org

This article is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare provider before starting any treatment, including hyperbaric oxygen therapy.