What Does Hyperbaric Oxygen Therapy (HBO) Feel Like?

June 24, 2026

If you’ve been referred for hyperbaric oxygen therapy and you’re wondering what to expect, you’re in good company. It’s completely natural to feel curious, or even a little nervous, about a treatment that takes place inside a pressurized chamber. The good news is that most patients are pleasantly surprised by how manageable and even relaxing the experience turns out to be. Whether you’re about to begin your first session or you’re simply doing your research, understanding what the HBO experience actually feels like can go a long way toward calming any worries before you ever walk through the door. 

This article walks you through real patient sensations and experiences, phase by phase, so you know exactly what’s coming. 

Understanding HBO Before You Experience It

Hyperbaric oxygen therapy (HBO) is a medical treatment in which you breathe 100% pure oxygen inside a pressurized chamber. The atmospheric pressure inside the hyperbaric oxygen chamber is raised to levels higher than what you experience at sea level, typically between 1.5 and 3 times the normal pressure. This allows your lungs to absorb far more oxygen than they could under ordinary conditions, which in turn saturates your blood and tissues with healing oxygen. 

HBO is FDA‑cleared for specific medical conditions, including non‑healing diabetic foot ulcers, radiation tissue injury, and certain chronic wounds that benefit from enhanced oxygen delivery to damaged tissue. Knowing the reasoning behind the treatment helps put the sensations you’ll feel into context because each physical change you notice is your body responding to a carefully controlled, therapeutic environment. 

The Physical Sensations You Might Feel During HBO

The HBO sensations patients most commonly describe fall into a few predictable categories: pressure, warmth, and occasionally taste. None of these are dangerous, and most are temporary. Here’s what to expect. 

That Pressure Feeling in Your Ears 

The most universally reported sensation during hyperbaric oxygen therapy is a feeling of fullness or pressure in the ears, very similar to what you feel when a plane descends or when you drive down a mountain. As the chamber pressurizes, the air pressure around you increases, and your middle ear needs to equalize to match it. 

For most people, this feeling is mild and passes quickly, especially once they learn simple equalization techniques. Swallowing, yawning, or gently performing a Valsalva maneuver (pinching your nose and blowing gently) all help. HBO technicians will walk you through these methods before your first session, so you’re never left guessing. 

Warmth and Temperature Changes

Another common HBO sensation is a feeling of warmth during the pressurization phase. As oxygen is compressed into the chamber, the temperature inside rises slightly, a basic law of physics at work. Most patients describe this as mild and not uncomfortable, and the warmth typically levels off once the chamber reaches its target pressure and stabilizes. The treatment environment is monitored and controlled throughout your session to keep you as comfortable as possible. 

A Slight Metallic Taste

Not everyone experiences this one, but it’s worth knowing about: some patients notice a faint metallic taste in their mouth during or shortly after an HBO session. This can occur because high concentrations of oxygen under pressure interact with trace elements in your saliva and tissues. It’s harmless, temporary, and tends to fade shortly after the session ends. If it bothers you, a small sip of water after treatment can help. 

Mental and Emotional Reactions You Might Experience

What does HBO feel like on an emotional level? The answer varies by person, but there are some experiences that come up again and again across patients. 

Initial Anxiety and How It Fades

It’s completely understandable to feel a flutter of anxiety before your first session. The HBO chamber is an enclosed space; the pressurization sounds can be unfamiliar, and anytime you’re in a medical setting, nerves can run high. What patients consistently report, though, is that this anxiety melts away quickly once the session is underway. The environment is calm, the process is controlled, and the team monitoring your treatment is attentive and communicative. Many patients who expected to feel claustrophobic are surprised to find the chamber quieter and more peaceful than they anticipated. 

A Sense of Calm and Relaxation 

Once the initial adjustment period passes, many patients find hyperbaric oxygen therapy unexpectedly relaxing. The chamber is quiet. You’re not expected to do anything. There are no phones ringing, no tasks demanding your attention; just steady breathing in a still, controlled environment. It’s not unusual for patients to drift off to sleep during their sessions. That sense of stillness is one of the aspects of the HBO experience that catches people most off guard in the best possible way. 

Anticipation of Healing

There’s a psychological dimension to HBO treatment that doesn’t get discussed as often as the physical sensations, but patients frequently mention it. When you’re in the chamber, you know that oxygen is actively reaching tissue that may have been deprived of it for weeks or months. The awareness that each session is contributing to your healing can create a genuine sense of hope and purpose. Many patients describe looking forward to their sessions not just as a habit but as an emotionally grounding part of their recovery. 

Common Sensations During the Pressurization Phase

The pressurization phase is when you’ll notice the most physical sensations. This is the transition from normal atmospheric pressure to the therapeutic level inside the HBO chamber. 

The Gradual Pressure Buildup 

Pressurization doesn’t happen all at once. It’s a slow, deliberate process and far more gradual than you might expect. Patients often liken it to descending in an airplane, but even gentler. The chamber fills with 100% oxygen over several minutes, and your body has time to adjust incrementally. Technicians watch the process closely and can slow the rate of pressurization if a patient needs more time to equalize. 

Body Adjustment and Equalization Techniques

During pressurization, your most active job is helping your ears equalize. Swallowing frequently is often enough. Yawning works well for many patients. If those don’t do the trick, the Valsalva maneuver, gently blowing against a pinched nose, helps open the Eustachian tubes and relieve the pressure sensation. Your HBO technician will review all these options with you before you ever get into the chamber. You won’t be navigating this alone. 

What You’ll Experience During the Treatment Phase 

Once the chamber has reached full pressure, the treatment phase begins. For most patients, this is the calmest part of the session. 

A Feeling of Stillness and Time 

Time has a way of moving differently inside the hyperbaric oxygen chamber. The environment is quiet. Your breathing is steady. Many patients report that their 90-minute sessions feel considerably shorter than they actually are. Some use the time to listen to music or watch a movie; others close their eyes and rest. There’s no pressure to stay alert or engaged. The chamber does the work. 

Subtle Energy Changes

Some patients report noticing a gentle tingling or subtle shift in how they feel physically as treatment progresses. This is often attributed to the elevated oxygen saturation in the bloodstream, which means more oxygen is reaching your tissues than they’re used to receiving. It’s usually a soft, pleasant sensation rather than anything jarring, and many patients interpret it as a reassuring sign that the HBO treatment is doing what it’s supposed to do. 

Minimal Discomfort or Distraction

It’s important to emphasize that for the vast majority of patients, the treatment phase is genuinely comfortable. The ear pressure from the start of the session has typically resolved by this point. The warmth from pressurization has evened out. You’re simply resting in an oxygenated environment while your body heals. If any discomfort does arise at any point during the session, technicians are available and attentive. Don’t hesitate to signal them. 

The Decompression Phase and Post-Treatment Sensations

As your session winds down, the chamber slowly returns to normal pressure in what’s called the decompression phase, a carefully controlled transition that is both safe and comfortable.  

Gradual Pressure Release

Just as pressurization was slow and incremental, so is the return to normal pressure. Your ears may pop gently again as the pressure releases, the same sensation you had on the way in, but in reverse. Most patients find this phase comfortable and relatively quick. The careful, controlled pace of decompression protects against any complications and gives your body a smooth transition back to baseline. 

Post-Treatment Fatigue or Energy

After stepping out of the HBO chamber, patients fall into two general camps: those who feel pleasantly relaxed and a bit sleepy, and those who feel refreshed and energized. Both are normal. Which one you experience may depend on your overall health, the condition being treated, and where you are in your course of therapy. Either way, post-treatment effects are typically mild and short-lived. If you feel tired, rest. If you feel energized, that’s a welcome bonus. 

Hunger and Appetite Changes 

A noticeable increase in appetite after HBO sessions is something patients mention more often than you might expect. Staying hydrated before and after your sessions and eating a light, balanced meal before treatment are both good practices that support your body’s response to hyperbaric oxygen therapy. 

How Individual Factors Influence Your HBO Experience

Does HBO feel the same  to everyone? Not quite. Your individual experience will be shaped by a range of personal factors. 

Your Anxiety Level and Mindset

Patients who approach HBO treatment with a calm and open mindset tend to find the experience easier from the start. That’s not to minimize any anxiety you might have — it’s real, and it’s understandable. But it does mean that doing some mental preparation can be beneficial. Simple breathing exercises, arriving a few minutes early to get oriented, and talking openly with your care team about any concerns can all make a meaningful difference. 

Your Overall Health Status

Where you are in your overall health journey affects how you perceive and tolerate HBO treatments. Patients who are more fatigued or who are managing multiple health challenges may find sessions more draining initially. As treatment progresses and healing occurs, many patients report that their sessions begin to feel easier, and their energy levels improve between appointments. 

Previous Experience with Medical Treatments 

If you’ve spent time in medical environments before, whether for other therapies, surgeries, or extended care, you may find the HBO chamber less intimidating than patients encountering it for the first time. Familiarity with the routines of clinical care, taking direction from technicians, and trusting the process can all help. First-time patients should know that it typically only takes one or two sessions before the whole experience starts to feel routine and manageable. 

Tips for Making Your HBO Experience More Comfortable

You’re not a passive participant in your HBO journey. There are concrete things you can do to set yourself up for a better experience. 

Preparation Strategies Before Your Session 

Wear loose, comfortable clothing to change out of—your center or hospital will likely provide cotton garments to change into, since synthetic fabrics aren’t permitted inside hyperbaric oxygen chambers. Eat a light meal one to two hours before your session to avoid going in hungry or overly full. Stay well hydrated throughout your treatment course. Avoid alcohol and caffeine on treatment days if possible, as both can affect how your body responds to oxygen therapy. And arrive a few minutes early, especially for your first few sessions, so you’re not rushing. 

During-Session Comfort Techniques

Equalize early and often during pressurization. Don’t wait until the pressure builds to a point of real discomfort. Breathe slowly and naturally throughout the session. If music or video options are available at your center, take advantage of them; having something gentle to focus on can make the time pass comfortably. And remember: your technician is monitoring you throughout the entire session. You are never alone in that chamber, even if it feels quiet. 

Post-Treatment Care and Recovery

Drink water after your session. If you feel hungry, eat something that is nourishing. Give yourself a few minutes before driving if you feel particularly relaxed or foggy. Over the course of your treatment plan, maintaining consistent sleep, hydration, and nutrition will support the cumulative results of hyperbaric oxygen therapy and help your body make the most of each session. 

When to Talk to Your Healthcare Provider About Your Sensations

Understanding which HBO sensations are expected and which ones warrant a conversation with your care team is an important part of being an informed patient. 

Normal Sensations to Expect

Ear fullness and popping during pressurization and decompression are normal. Mild warmth during the early phase of treatment is normal. A feeling of deep relaxation or light fatigue after sessions is normal. An increased appetite is normal. A faint metallic taste, if it appears, is normal. Subtle tingling or energy shifts during treatment are normal. These are all signs that your body is responding to a significant change in pressure and oxygen environment, exactly as expected. 

Sensations That Warrant Medical Attention

Certain experiences fall outside the range of what’s typical and should always be reported promptly. Severe or persistent ear pain (not just fullness, but genuine pain) should be flagged immediately. Chest tightness or difficulty breathing during a session requires immediate communication with your technician. Severe dizziness, vision changes, or unusual confusion are all reasons to alert your care team right away. These events are uncommon, but HBO staff are trained specifically to respond to them. Your safety is the technician’s priority, and no concern is too small to mention. 

Wrapping Up: What to Expect on Your HBO Journey

So, what does HBO feel like? For most patients: a gentle pressure in the ears during the first and last few minutes, a brief warmth as the chamber pressurizes, and then a long, calm, quiet stretch of resting while your body receives significant increases in the amount of oxygen dissolved in your blood and delivered to tissues. It feels, for many people, like an unexpected oasis of stillness on an otherwise busy day. 

The physical HBO sensations are manageable. The emotional arc from initial uncertainty to growing confidence to genuine anticipation of healing is one that patients repeatedly describe . You may be nervous before your first session. By your fifth, many patients are settling in with music and falling asleep before the chamber even finishes pressurizing. 

You don’t have to take it all on faith. Your care team is with you at every step answering questions before treatment begins, guiding you through equalization techniques, monitoring you throughout every session, and supporting your recovery from start to finish.

The HBO experience is one that gets more familiar and more comfortable with time. And for many patients, it has become one of the most meaningful parts of their healing journey. Being prepared helps you take an active, confident role in your care, and that’s truly something to feel good about. Our wound care specialists can help evaluate the next best steps. Find a Wound Care Center® near you.