What to Expect at Your First Hyperbaric Oxygen Therapy Session
Your first HBOT session involves a medical screening, 90-120 minutes in a pressurized chamber, and ear equalization. Here's exactly what happens, step by step.
What to Expect at Your First Hyperbaric Oxygen Therapy Session
Most people don’t know what to expect at their first hyperbaric chamber session. The equipment looks unfamiliar. The pressurization feels odd. And 90 minutes is a long time if you’re not prepared.
What follows covers exactly what happens, from the moment you arrive to the moment you leave.
Before Your Appointment
Preparation starts at home. A few things matter for safety in a high-oxygen environment.
Don’t use petroleum-based products. No petroleum jelly, oil-based lotions, hairspray, or perfumes. These products are flammable in an oxygen-enriched environment. Skip them on the day of your session.
Wear 100% cotton clothing. Some facilities provide cotton garments. If yours doesn’t, wear natural fibers. Synthetic fabrics like polyester can generate static, which is a risk around pure oxygen.
Leave electronics and jewelry at home or in your locker. No phones, smartwatches, hearing aids (in most cases), or metal jewelry allowed inside the chamber.
Eat normally. Don’t fast before your session, but don’t eat a huge meal right before either. A normal, moderate meal a couple of hours before works fine.
Before your very first session, the staff will review your medical history, current medications, and any potential contraindications. You’ll sign an informed consent form. This usually takes 15-30 minutes.
What Happens During Your Session
A standard HBOT session has three phases: pressurization, treatment time at pressure, and depressurization. The whole thing takes 90-120 minutes.
Pressurization (10-15 minutes). The chamber slowly pressurizes to your treatment pressure, typically 2.0-3.0 ATA depending on your condition. This is where you’ll feel your ears needing to equalize, just like descending in an airplane.
Your care team will teach you how to equalize before you get in. The most common techniques are swallowing, yawning, or the Valsalva maneuver (gently blowing with your nose pinched and mouth closed). Don’t force it. Tell the technician if you’re struggling, and they can slow the pressurization.
Treatment time at pressure (60-90 minutes). Once you reach treatment pressure, you breathe 100% oxygen. In a monoplace chamber, you breathe it directly. In a multiplace chamber, you breathe through a mask or hood.
Most people watch TV, listen to music, or rest. You’ll be monitored throughout. If you’re in a monoplace chamber, you can talk to staff via intercom at any time.
Depressurization (10-15 minutes). Pressure slowly returns to normal. Your ears may need to equalize again during this phase.
The Two Types of Hyperbaric Chambers
You’ll be treated in one of two chamber types, depending on your facility.
Monoplace chambers hold one person. You lie down inside a clear acrylic tube. The chamber fills with 100% oxygen, and you breathe it directly. It feels like lying in a large, transparent tube. Monoplace chambers are common at standalone clinics and some hospital programs.
Multiplace chambers are room-sized. Several patients and at least one attendant can be inside at the same time. The chamber pressurizes with air, and each patient breathes 100% oxygen through a mask or hood. These are common at hospital-based hyperbaric programs and military facilities.
Both types deliver the same medical HBOT treatment. The main practical difference is the social environment and how you breathe the oxygen.
After Your Session
There are no activity restrictions after a session. You can drive yourself home. You can return to work.
Some patients feel tired after early sessions. This usually passes within the first week of treatment as your body adjusts. Others feel energized. Both are normal responses.
HBOT effects are cumulative. Don’t expect dramatic changes after one session. For wound healing, your care team will measure progress at regular intervals. For most conditions, meaningful improvement shows up after 10-20 sessions.
Session frequency is usually five days a week, Monday through Friday. Acute conditions like carbon monoxide poisoning or decompression sickness may require multiple sessions in a single day.
For more on how long your treatment course might run, read How Many Sessions Do You Need?
To understand potential side effects, read Side Effects and Risks of HBOT.
You can also find a hyperbaric provider near you if you haven’t started treatment yet.
Frequently Asked Questions
Is it claustrophobic inside a hyperbaric chamber?
Monoplace chambers are enclosed, which can feel uncomfortable for some people. Tell your care team if you have claustrophobia before your first session. They can discuss options, including the possibility of anti-anxiety medication to help you tolerate treatment.
Can I bring my phone in the chamber?
No. Electronics aren’t allowed due to fire risk in an oxygen-rich environment. Most facilities provide TV or music inside the chamber so you have something to do during the session.
Will I feel anything during the session?
You’ll feel your ears needing to equalize during pressurization, similar to flying. Some people feel warm during compression. Most feel relaxed once at pressure. Some report mild tiredness after early sessions that usually passes within a few days.
How soon will I see results?
HBOT effects are cumulative. Most patients don’t see significant improvement until after 10-20 sessions. For wound healing, progress is measured at each visit using wound size and tissue oxygen readings.
Medical Disclaimer: This page is for informational purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider before pursuing any medical treatment.