What to Expect During Your First HBO Session: A Patient’s Guide

May 1, 2026

Introduction to Your First HBO Session

Starting something new in a medical setting can bring up a lot of feelings, including curiosity, hopefulness, and even a little anxiety. If you’re preparing for your first HBO session, you’re not alone wondering what’s going to happen when you walk through those doors. The good news is that hyperbaric oxygen therapy is a well-established, carefully monitored treatment, and the more you know going in, the more comfortable you’re likely to feel.

This guide is designed to walk you through the entire experience from beginning to end. We’ll cover how to prepare before your appointment, what you’ll see and feel once you’re inside the chamber, what to expect after your session wraps up, and how to make each visit a little easier. Think of it as a friendly, plain-language roadmap for a journey that, for many patients, becomes a routine part of their week.

Whether your provider recommended this therapy for a non-healing wound, radiation injury, or another medically qualifying condition, the goal is the same: to give your body more of what it needs to heal. Understanding what’s involved is a big part of getting there.

Understanding What HBO Therapy Is

Hyperbaric oxygen therapy is a medical treatment in which you breathe 100% pure oxygen inside a pressurized chamber. Under normal conditions, oxygen travels through your bloodstream primarily attached to red blood cells. But when the air pressure around you is increased, typically to two or three times normal atmospheric pressure, oxygen dissolves directly into your blood plasma, cerebrospinal fluid, and other body fluids. This allows oxygen to reach areas where blood flow may be restricted or compromised.

For patients dealing with wounds that aren’t healing properly, this boost in oxygen delivery can make a meaningful difference. Oxygen is essential to the cellular processes that repair tissue, fight infection, and build new blood vessels. When a wound site isn’t getting enough of it, healing stalls. HBO therapy works to change that equation.

If you’d like a deeper look at the mechanics, How Does Hyperbaric Therapy Work is a great resource for understanding the science in more detail. And for an overview of outcomes, Hyperbaric Oxygen Therapy Improves Healing outlines what patients can expect as treatment progresses.

Pre-Session Preparation: Getting Ready for Your Appointment

Good preparation makes a real difference in how smoothly your first HBO session goes. There are a few practical things to take care of before you arrive, and most of them are straightforward once you know what to expect.

Plan to arrive a little early, 15 to 20 minutes is usually enough, so you have time to complete any intake paperwork without feeling rushed. The staff will want to review your medical history, go over safety protocols, and answer any questions you have before the session begins. That check-in time is genuinely useful, especially for first-time patients, allowing for time to get settled.

Your care team will give you specific instructions tailored to your individual situation. The guidelines below are general and meant to give you a solid starting point.

What to Bring and What to Avoid

What to bring:

Bring a valid photo ID and your insurance card. A list of your current medications can also be helpful for the intake review.

Wear loose, comfortable clothing made from 100% cotton. Natural fibers are preferred because synthetic fabrics, polyester, nylon, and similar materials can generate static electricity, which is a safety concern in an oxygen-enriched environment. Your facility may provide a cotton gown if your clothing doesn’t meet guidelines, so don’t stress if you’re unsure.

What to leave at home or in your car:

The HBO chamber environment has strict safety requirements related to its high-oxygen atmosphere. Before entering, you’ll be asked to remove or leave behind:

Electronics & Powered Devices

Mobile phones, tablets, smart watches, and fitness trackers
Hearing aids or devices with batteries (your team will review approved options)
E‑cigarettes, vapes, or electronic smoking devices

Personal Care Products

Petroleum‑based products, including:
Oil‑based lotions or creams
Lip balm or Vaseline
Hair products containing oils, waxes, gels, or pomades
Makeup, including foundation, mascara, and eyeliner
Nail polish, artificial nails, or nail adhesives
Perfume, cologne, or heavily scented hair spray
Hair should be clean and free of all styling products

Clothing & Accessories

Synthetic or blended fabrics (polyester, nylon, spandex, fleece)
Jewelry, watches, hair clips, metal accessories, or body piercings
Wigs or hairpieces not made from natural fibers

Fire & Safety Hazards

Lighters, matches, or any fire‑starting items

Vision & Medical Items

Contact lenses (many centers prefer glasses instead)
Adhesive patches or external medical devices (such as nicotine or heating patches. Your care team will advise what is safe)

Tobacco & Nicotine

Smoking, vaping, or use of nicotine products before treatment

These restrictions may vary by facility. They exist to protect you and everyone else in the facility. The staff will guide you through any specific requirements at your location.

Dietary and Hydration Guidelines

What you eat and drink before your HBO session can affect how comfortable you are during treatment. Here are some general guidelines:

Do eat something. Arriving on an empty stomach isn’t recommended, as low blood sugar can make you feel lightheaded in the chamber. A light, balanced meal a couple of hours before your appointment is a good approach.

Avoid heavy or rich foods in the hours before your session. Large meals can cause bloating and gas, which can become uncomfortable when you’re in a pressurized environment. Your digestive system is still doing its thing, and a full stomach adds to that.

Skip carbonated beverages on treatment days. The carbonation can contribute to bloating and general GI discomfort during pressurization.

Limit caffeine. Excessive caffeine can increase anxiety and may affect how your body responds to the oxygen therapy. A single cup of coffee is generally fine for most patients but check with your care team if you have concerns.

Drink plenty of water. Hydration supports your body’s ability to circulate oxygen effectively. Aim to be well-hydrated going in, not thirsty, but not uncomfortably full of fluids either.

Your provider may have additional or different instructions depending on your diagnosis or any other health conditions you’re managing. Always follow their specific guidance over general advice.

Arrival and Check-In Process

When you arrive at the wound care center for your first HBO appointment, you’ll be welcomed by staff who are experienced with patients at every comfort level, including those who are nervous. The check-in team sees first-timers regularly and helping you feel at ease is part of what they do.

During check-in, a staff member will:

Confirm your medical history and go over any updates since your referral
Review your current medications, including over-the-counter supplements
Explain the session process and what you’ll experience step by step
Walk through safety rules and answer questions about the chamber
Conduct a brief physical check, which may include blood pressure and blood glucose measurements for certain patients

This is a great moment to voice any concerns you have. If you feel anxious about enclosed spaces, let them know. They have strategies to help make the experience more manageable. If you have any new symptoms or health changes since your last provider visit, mention those as well.

After check-in, you’ll be asked to change into appropriate clothing if needed, remove restricted items, and get ready to head into the treatment area. The whole process is designed to help you feel informed and prepared before you ever step near the chamber.

Your First HBO Session: The Step-by-Step Experience

Here’s where the process really comes to life. Understanding what happens at each stage of your HBO session makes the experience feel much less like a mystery and more like a manageable sequence of events. Let’s walk through it.

Entering the Hyperbaric Chamber

HBO chambers come in two main types. A monoplace chamber is designed for one person and looks something like a clear, cylindrical tube — you lie down on a padded surface and slide in. A multiplace chamber is larger and can accommodate several patients at once, along with a staff member who remains inside throughout the session. Both are safe and effective; the type you use will depend on your facility.

Once you’re in place, staff will ensure you’re comfortable and positioned correctly. In a monoplace chamber, the entire chamber fills with oxygen, so you breathe in naturally. In a multiplace chamber, you breathe oxygen through a mask while the chamber is pressurized with air.

You’ll be able to communicate with the technician throughout your treatment. Monoplace chambers typically have an intercom system, and multiplace chambers have a staff member physically present. You are never alone and never out of reach.

The Pressurization Phase

Once you’re settled, the chamber will begin to pressurize. This is the part of the process that most patients notice first, and it’s helpful to know what’s coming.

As the pressure increases, you’ll likely feel a sensation of fullness or pressure in your ears, similar to what you experience when a plane descends or when you dive underwater. This happens because the pressure change affects the air space in your middle ear. Staff will show you how to equalize this pressure before your session begins; the techniques are simple, like yawning, swallowing, or gently pinching your nose and blowing slowly.

You may also notice a mild warming sensation as the chamber pressurizes, and possibly some creaking or whooshing sounds from the equipment. All of this is completely normal. The pressurization phase typically takes around 10 to 15 minutes, depending on your prescribed pressure level.

If at any point the ear pressure becomes more than mildly uncomfortable, you can signal to the technician, and pressurization can be slowed or briefly paused. Your comfort matters, and the staff is paying close attention throughout.

The Treatment Phase

Once the chamber reaches its target pressure, the main treatment begins. For most patients, this phase lasts approximately 90 to 120 minutes, though the exact duration depends on your treatment plan and the condition being addressed.

The goal is simply to relax and let the therapy do its work. Many patients listen to music, watch a movie or TV show (many facilities have screens visible from inside the chamber), or simply rest or nap. It can actually be a surprisingly peaceful stretch of time once you get used to the environment.

You don’t need to do anything specific during this phase. Your job is just to breathe normally. If anything feels off, you can always let the technician know. They’re monitoring you throughout and are ready to respond if you need anything.

The Decompression Phase

When the treatment time is complete, the chamber will gradually return to normal atmospheric pressure. This process, called decompression, takes roughly the same amount of time as pressurization, usually 10 to 15 minutes. You may experience the same mild ear sensations as the pressure decreases, and the same equalization techniques apply.

Decompression is a critical part of the therapy and isn’t something to rush. The gradual return to normal pressure ensures your body adjusts safely. Once the chamber is fully depressurized and the door is opened, you’ll be helped by a staff member and taken to a recovery or seating area.

That’s it — your first session of HBO therapy is complete!

Common Sensations and What They Mean

Knowing what’s normal can go a long way toward keeping you calm during treatment. Here’s a quick rundown of sensations patients commonly report and what they actually mean:

Ear pressure or fullness: This is one of the most consistently reported experiences during the first HBO session. It’s caused by the pressure differential affecting your middle ear, and it resolves as you equalize. If you can’t equalize, alert the tech.

Mild warmth: The increased pressure raises the temperature inside the chamber slightly. It’s usually not dramatic, but you may notice it.

Temporary vision changes: Some patients who undergo many sessions of HBO therapy notice minor changes in their near or distance vision. This is a well-documented, temporary side effect related to the effect of high-pressure oxygen on the lens of the eye. Vision typically returns to baseline within a few weeks of completing treatment. Your care team will monitor for this.

Mild dizziness or lightheadedness: Usually brief and most common during the pressurization or decompression phases. It resolves quickly.

A sense of calm or drowsiness: Breathing high-concentration oxygen in a quiet environment has a relaxing effect on many people. Falling asleep during treatment is completely fine.

None of these sensations are cause for alarm. If something feels significantly uncomfortable or different from what you were told to expect, communicate with your technician, but the experiences above are a routine part of the process.

What to Expect After Your First HBO Session

For most patients, the transition out of the chamber is smooth and uneventful. You may feel completely normal, or you might notice a few mild effects.

Fatigue: Some patients feel pleasantly tired after their first HBO session, especially if they relaxed deeply or fell asleep. This typically fades within a few hours, and most people resume normal activities the same day.

Temporary sinus pressure: If you have any congestion or seasonal allergies, the pressure changes can leave your sinuses feeling a bit full or tender. This usually resolves on its own.

Hunger: If it’s been several hours since you ate, you may feel noticeably hungry after your session. That’s normal and a good sign that your body is metabolically active.

After your session, drink water, eat something if you haven’t, and take it easy for the remainder of the day if your schedule allows. Most people are back to their routine without any issues.

Call your care team if you experience chest pain, severe headache, difficulty breathing, or any other symptoms that feel significant. These are rare, but it’s always better to check in when something feels wrong.

Potential Side Effects and How to Manage Them

HBO therapy is a very safe treatment when administered in a clinical setting by trained professionals, but like any medical therapy, it can come with some side effects. Being aware of them helps you manage them confidently if they arise.

Claustrophobia: The enclosed space of the chamber is the most common source of anxiety for first-time patients. If you have a history of claustrophobia, tell your care team before your session. Many facilities can offer mild sedation, distraction strategies, or positioning adjustments that make the experience much more manageable. Monoplace chambers are clear, and many patients find that being able to see out makes a significant difference.

Ear discomfort: If you have difficulty equalizing pressure due to congestion, eustachian tube issues, or anatomy, you may experience more ear discomfort than the average patient. Your team may recommend decongestants or modify the pressurization rate to accommodate your needs.

Mild headache: Usually related to changes in oxygen concentration and typically resolves within an hour or two. Hydration helps.

Serious complications are uncommon. The medical team’s training and monitoring protocols are in place specifically to catch and address anything unusual before it becomes a problem. The development of these safety standards over decades of practice means you’re in capable, experienced hands.

Questions to Ask Your Healthcare Team

Coming prepared with questions helps you get the most out of your care. Here are some worth raising before, during, or after your first HBO session:

Before treatment:

How many sessions will I likely need, and how often will I come in?
What results should I realistically expect, and over what timeframe?
Are there any specific preparation steps I should take given my particular condition or medications? What should I do if I feel claustrophobic or uncomfortable in the chamber?

During treatment:

How will I communicate with you once I’m inside the chamber?
What should I do if my ears won’t equalize?
Is it okay to sleep during the session?

After treatment:

Are there activities or foods I should avoid between sessions?
What signs of progress should I be watching for?
When should I contact the clinic between appointments?
How will you be monitoring my wound and overall response to treatment?

The answers to these questions are also part of the broader success of your treatment plan. Your care team wants you to be engaged and informed — don’t hold back.

Tips for Making Your Sessions More Comfortable

By the time you’ve had a few HBO sessions, most patients find that the process feels fairly routine. But there are things you can do from the very beginning to make the experience easier.

Practice relaxation techniques. Deep, slow breathing is genuinely helpful, both as an equalization strategy during pressurization and as a way to calm your nervous system if you feel anxious. Some patients find that a brief mindfulness practice before arriving helps set a calmer tone for the visit.

Bring something to listen to. If your facility allows it, many patients enjoy listening to podcasts, audiobooks, or music during their session. It makes the 90 to 120 minutes pass more quickly. Devices must be approved by staff for safety, so ask about your facility’s specific offerings or policies.

Communicate freely with your care team. If something bothers you about the process, whether the sounds, the ear pressure, the positioning, or anything at all, say so. The staff can often make small adjustments that significantly improve your comfort. You don’t have to silently tough anything out .

Don’t skip meals before your session. It sounds small, but arriving well-fed and hydrated makes a real difference in how you feel during and after the session.

Give yourself a little grace. It’s normal for the first HBO episode to feel a bit strange or unfamiliar. Most patients feel notably more at ease by their second or third visit. You’re experiencing something new, and that takes a moment to settle into.

You’re Ready for Your First HBO Session

Here’s what’s worth remembering as you head toward your appointment: the medical staff at your Wound Care Center® has guided countless patients through this exact experience. They’ve seen the full range of reactions, from patients who fall asleep in the chamber to those who needed a few extra minutes to feel comfortable, and they’re prepared for all of it.

Feeling nervous before your first HBO session is completely normal. It doesn’t mean something will go wrong; it just means you’re human. Let the team know how you’re feeling, follow the preparation guidelines you’ve been given, and trust that the process is well-designed and well-monitored.

HBO therapy has a long track record of supporting healing in patients who haven’t responded to other treatments. The development of clinical programs and protocols over many decades reflects both the effectiveness of the therapy and the commitment of wound care professionals to delivering it safely. You’re in good hands, and each session builds on the last.

Follow your care team’s pre- and post-treatment guidance, show up consistently, and ask questions when you have them. That’s really all that’s required of you. The rest is what the therapy is for.

Have questions about oxygen therapy or hyperbaric treatment? Are you coping with a slow-healing wound? Our wound care specialists can help evaluate the next best steps. Find a Wound Care Center® near you.