Hyperbaric oxygen therapy puts your whole body under pressure and floods it with oxygen, which is exactly why chronic obstructive pulmonary disease (COPD) changes the safety calculation. COPD damages the lungs in two ways that matter inside a hyperbaric chamber: it traps air in stiff, over-stretched air sacs, and it can blunt the body's ability to clear carbon dioxide. This guide walks through what those two problems mean during pressurization, what the published data actually show about how often things go wrong, and how to decide whether HBOT is reasonable for someone with lung disease.
Why COPD Is a Special Case for HBOT
Most healthy lungs handle pressure changes without trouble. You equalize the same way you do on an airplane or in a swimming pool. COPD breaks that easy adjustment in two specific ways, and both of them get amplified inside a chamber.
The first problem is mechanical. COPD often comes with emphysema, which destroys the walls between air sacs and leaves behind enlarged pockets of trapped air called bullae (a smaller version is a bleb). Healthy lungs empty and fill smoothly. Lungs with bullae and narrowed, floppy airways do not. Air gets in but struggles to get back out. That matters because of a basic gas law: when the pressure around you drops, trapped gas expands. In a hyperbaric chamber, the dangerous moment is decompression (the ascent back to surface pressure at the end of a session), when any trapped pocket of air swells. If it can't vent through the airway fast enough, it can over-stretch and rupture lung tissue. That event is called pulmonary barotrauma.
The second problem is chemical. Many people with advanced COPD live with chronically high carbon dioxide (CO2) in their blood, a state called chronic hypercapnia. Giving these patients large amounts of oxygen can, in some cases, push their CO2 even higher. HBOT delivers oxygen at concentrations and pressures far beyond a nasal cannula at home, so the theoretical concern is real and worth understanding.
Neither problem makes COPD an absolute "never." But together they move COPD into the category of a relative contraindication — something that requires a careful, individual risk-benefit decision rather than a routine green light. For the bigger picture on when HBOT crosses from cautious to genuinely off-limits, see our deep dive on HBOT contraindications: when it's genuinely dangerous.
Problem One: Trapped Air and Barotrauma
How the chamber turns trapped air into a hazard
Boyle's Law is the whole story here. Gas volume rises as pressure falls. A typical clinical HBOT session compresses you to roughly 2.0 to 2.4 atmospheres absolute (ATA), then holds you there, then slowly brings you back to 1.0 ATA. During the hold and on the way down (compression), trapped gas is squeezed and any small pocket actually shrinks. The risk window opens on the way back up — decompression — when that gas re-expands.
In a normal lung, the airways are open enough that expanding gas simply flows out as you breathe. In COPD with significant air trapping or large bullae, a pocket of gas can be partly sealed off behind a collapsed or obstructed airway. As that pocket expands on ascent, the pressure inside it climbs against lung tissue that has nowhere to vent. Three bad outcomes can follow:
- Pneumothorax — air escapes into the space between the lung and chest wall and the lung collapses.
- Pneumomediastinum — air leaks into the center of the chest.
- Arterial gas embolism (AGE) — gas forces its way into a blood vessel and travels to the brain or heart. This is the most feared outcome.
A simple untreated pneumothorax is itself the one truly absolute reason never to start HBOT, because pressurization can turn a small collapsed lung into a life-threatening tension pneumothorax.
What the numbers actually say
Here is where the honest version of the story matters, because the theoretical risk and the measured risk are not the same size.
Pulmonary barotrauma during HBOT is rare, even though chamber programs treat a large number of patients who have some degree of lung disease. The most useful real-world dataset comes from a multicenter review of standard hyperbaric practice. Across roughly 62,040 treatments on 2,250 patients at three North American centers, there was a single documented case of pulmonary barotrauma — a rate of about 0.0016% per treatment, or about 0.044% per patient (routine pulmonary imaging review, Diving and Hyperbaric Medicine 2022, PMID 36100931).
A separate international survey of 98 hyperbaric centers — covering around two million oxygen exposures — found 9 cases of barotrauma, a rate near 0.00045%. Notably, 65 of those 98 centers (66%) reported deliberately treating patients who had known air cysts (bullae or blebs) in their lungs, and even so the barotrauma rate stayed extremely low (Toklu et al., Respiratory Medicine 2008, PMID 18571913).
A 2025 analysis reached the same conclusion using more recent data: pneumothorax occurred in about 0.0059% per session (0.15% per patient), and air-containing lesions including bullae were not associated with an increased barotrauma risk under standard treatment protocols (Türkmen et al., Diving and Hyperbaric Medicine 2025, PMID 41364858).
So the honest reading is this: barotrauma is a serious event, but it is uncommon, and bullae alone — discovered incidentally on a scan in someone without symptoms — do not appear to be the predictor many people assume. The patients who do get hurt tend to have known, significant underlying lung pathology, not a small incidental bleb.
It also helps to keep the denominator in mind. These rates come from programs that already screen patients and that control the speed of decompression. A slow, controlled ascent gives trapped gas time to vent through the airway as it expands, which is part of why the numbers stay low. A rushed decompression — or a patient who holds their breath during ascent — removes that safety margin. The takeaway isn't "barotrauma can't happen," it's that the combination of careful screening plus a controlled descent profile keeps it vanishingly rare even in a population that includes many people with lung findings.
| Data source (year) | Population | Barotrauma / pneumothorax rate | Takeaway |
|---|---|---|---|
| 98-center survey (2008, PMID 18571913) | ~2,000,000 exposures, 9 cases | ~0.00045% per exposure | 66% of centers treat patients with lung air cysts; rate still very low |
| 3-center North American review (2022, PMID 36100931) | 62,040 treatments, 2,250 patients, 1 case | ~0.0016% per treatment; ~0.044% per patient | Routine imaging "of low value" for low-risk patients |
| Single-center analysis (2025, PMID 41364858) | Pneumothorax cases reviewed | ~0.0059% per session; 0.15% per patient | Bullae not linked to higher risk under standard protocols |
Why "rare" still doesn't mean "ignore it"
The low average rate hides the fact that risk is not evenly spread. A 0.0016% rate across a mostly-screened population says little about a specific person with severe, symptomatic emphysema and large bullae. The data tell us that routine chest CT screening of every healthy patient isn't worth it, because incidental lung findings are common (one review noted blebs and bullae appear in anywhere from 2.3% to 24.6% of people) and almost none cause trouble. The same data do not tell a person with advanced bullous emphysema that they're safe. That distinction is the entire point of calling COPD a relative contraindication.
Problem Two: CO2 Retention and the Oxygen Paradox
The counterintuitive risk of too much oxygen
For most conditions, more oxygen is better. In a subset of people with severe COPD, too much oxygen can actually make breathing worse by allowing carbon dioxide to build up. This is oxygen-induced hypercapnia. It's the same reason emergency medicine targets a careful oxygen saturation range (often 88–92%) rather than 100% for COPD patients in a flare.
The old explanation — that these patients breathe only because low oxygen "drives" them, and that giving oxygen removes that drive — turns out to be the smallest part of the picture. Current understanding points to three mechanisms working together (oxygen-induced hypercapnia mechanism review, NYU Clinical Correlations; see also LITFL: oxygen and CO2 retention in COPD):
- Ventilation-perfusion (V/Q) mismatch — the largest contributor. Diseased lungs normally shunt blood away from poorly ventilated areas (hypoxic pulmonary vasoconstriction). Extra oxygen relaxes that protective reflex, so blood flows back to lung zones that can't clear CO2 well, raising blood CO2.
- The Haldane effect — oxygen-loaded hemoglobin holds less CO2, releasing it into the blood. By some estimates this accounts for roughly a quarter of the rise.
- Reduced minute ventilation — the actual "breathing less" effect, now considered the smallest factor.
Why HBOT raises the stakes
HBOT doesn't deliver a little extra oxygen. It delivers near-100% oxygen at two-plus times normal pressure, dissolving far more oxygen into the blood than any home setup. For someone who already retains CO2, that's a much bigger oxygen load than the supplemental oxygen they may use daily. If their CO2 climbs during a session, the consequences range from drowsiness and confusion to CO2 narcosis — and inside a sealed monoplace chamber, a sedated patient who can't protect their airway is a genuine emergency.
This is exactly why StatPearls lists COPD as a relative contraindication "due to the risk of hypercarbia," noting that "increased oxygen levels can lead to oxygen-induced hypoventilation and exacerbation of ventilation/perfusion (V/Q) mismatch" (StatPearls: HBOT contraindications). The same reference classifies asymptomatic bullae, blebs, and a history of spontaneous pneumothorax as relative contraindications too.
It's worth being precise: not every COPD patient retains CO2. Many people with mild or moderate COPD have normal CO2 levels and tolerate oxygen fine. The hypercapnia concern is concentrated in severe disease with documented chronic CO2 retention, which is why an arterial blood gas (ABG) test, not just a saturation reading, is the relevant screening tool. A pulse oximeter on the finger tells you oxygen saturation but says nothing about CO2 — a retainer can look perfectly "saturated" while their carbon dioxide quietly climbs. Only a blood gas catches that.
There's also a sequencing difference worth understanding. A home oxygen concentrator might add a couple of liters per minute through a nasal cannula. HBOT raises the partial pressure of oxygen many times higher than that. So a patient who tolerates daily home oxygen without any CO2 trouble cannot assume the same response inside a chamber — the dose is in a different league. That's the core reason "I already use oxygen at home and I'm fine" is not, by itself, evidence that HBOT will be safe. The chamber is a more aggressive oxygen challenge, and the body's CO2-handling has to be re-checked against that higher load.
How a Good Program Screens a COPD Patient
A responsible hyperbaric program treats a COPD evaluation as a two-part question: can this person's lungs handle the pressure swings, and can they clear CO2 under a heavy oxygen load? Here's what that workup typically covers and why.
| Step | What it checks | Why it matters for COPD |
|---|---|---|
| Detailed history and physical | Smoking history, prior pneumothorax, severity of COPD, current symptoms | Past medical history predicts risk far better than imaging in low-risk patients |
| Pulmonary function tests (spirometry) | Degree of airflow obstruction and air trapping | Quantifies how "stiff" and over-inflated the lungs are |
| Arterial blood gas (ABG) | Baseline CO2 and oxygen levels | Identifies chronic CO2 retainers who risk oxygen-induced hypercapnia |
| Chest imaging (selective, not routine) | Large bullae, blebs, untreated pneumothorax | Reserved for symptomatic or high-risk patients; routine CT is low-value |
| Risk-benefit discussion + informed consent | Whether the indication justifies the risk | Confirms HBOT is genuinely needed (e.g., an approved indication) vs. elective wellness use |
Two points deserve emphasis. First, the literature repeatedly concludes that routine chest CT or X-ray screening of every patient is not warranted — it generates false positives and rarely changes the outcome. Imaging is for the patient whose history or symptoms raise a flag, not for everyone. Second, the strength of the indication matters enormously. An emergency or approved indication like carbon monoxide poisoning or a non-healing diabetic wound can justify accepting added pulmonary risk. An elective, unproven "wellness" use does not justify the same risk in a fragile COPD patient. For how that benefit side of the ledger is weighed, our HBOT safety profile from published trials lays out the complication data across conditions.
Inside the session: what monitoring looks like
Screening before treatment is only half the job. A COPD patient cleared for HBOT should also be treated in a way that catches trouble early during the session itself. In a multiplace chamber, where staff are inside with the patient, a clinician can watch breathing effort and responsiveness directly. In a monoplace chamber, where the patient is alone in a sealed acrylic tube, the staff outside rely on visual observation and communication through an intercom — which is exactly why a CO2 retainer who becomes drowsy is more concerning there, since they can't easily be reached mid-treatment. This chamber-type distinction is one reason a fragile pulmonary patient may be steered toward a setting where hands-on intervention is faster.
Treatment programs also build in air breaks — short periods breathing normal air partway through a session — primarily to reduce oxygen-toxicity risk to the lungs and central nervous system. For a COPD patient, those breaks also give the respiratory system brief windows at a lower oxygen load. None of this eliminates the underlying physiology, but it shows why "where and how" a COPD patient is treated matters as much as "whether." Our overview of oxygen toxicity in HBOT and its real risks explains why those air breaks exist in the first place.
Mild HBOT, Soft Chambers, and COPD
A common question: does a low-pressure "mild HBOT" soft chamber sidestep these risks? Partly, and not entirely.
Soft-shell chambers usually run at low pressure (around 1.3 ATA) and often deliver concentrated oxygen rather than 100% medical oxygen. Lower pressure means a smaller gas-expansion problem on decompression, which somewhat reduces barotrauma risk compared with a hard chamber at 2.4 ATA. But "smaller" is not "zero." Boyle's Law still applies, and trapped air in a bulla still expands on ascent — just less dramatically. The oxygen load is also lower, which reduces (but doesn't eliminate) the hypercapnia concern.
The bigger issue with soft chambers and COPD is supervision. Hospital and accredited clinic programs that take on a COPD patient do so with a physician evaluation, ABG data, and trained staff who can respond inside the chamber. A consumer soft-chamber setup at home offers none of that. A person with significant COPD who buys a home unit and self-treats has skipped exactly the screening that makes the relative-contraindication call safe. For the broader debate on these devices, see mild HBOT vs. medical HBOT: why 1.3 ATA is controversial.
Who Should and Shouldn't Consider HBOT With COPD
This isn't medical advice for any one person — the decision belongs to a hyperbaric physician who has seen the actual labs and scans. But the published picture supports a few general patterns.
Reasonable to consider, with proper screening and a real indication:
- Mild to moderate COPD with normal CO2 on ABG, no large bullae, and a recognized indication for HBOT.
- An incidental small bleb found on imaging in an otherwise stable patient, since the data don't link incidental lesions to barotrauma.
- A genuine emergency indication (such as carbon monoxide poisoning) where the benefit clearly outweighs pulmonary risk and the team is prepared to manage complications.
Reasons to pump the brakes or say no:
- Untreated pneumothorax — the one absolute stop. HBOT cannot proceed until it's resolved.
- Severe COPD with documented chronic CO2 retention, where oxygen-induced hypercapnia and CO2 narcosis are real risks.
- Large or symptomatic bullous emphysema, especially with a prior spontaneous pneumothorax.
- Anyone pursuing HBOT for an unproven elective use — the marginal possible benefit rarely justifies adding pulmonary risk to lungs that are already compromised.
Age and overall frailty fold into this too, since COPD and other risks often travel together; our note on HBOT for elderly patients and safety considerations covers that overlap. And if you're working through eligibility from scratch, the HBOT candidate and eligibility guide is a sensible starting point.
The Bottom Line on COPD and HBOT
COPD changes the safety math because it stacks two distinct risks — air trapping that can rupture under decompression, and CO2 retention that can worsen under heavy oxygen. Neither makes HBOT impossible. The measured rate of pulmonary barotrauma is genuinely low even at centers that treat lung-disease patients, and incidental bullae alone don't appear to drive that risk. What separates a safe treatment from a dangerous one is screening: a history and physical, spirometry, an arterial blood gas to catch CO2 retainers, selective imaging for symptomatic patients, and an honest look at whether the indication is strong enough to justify any added risk. The patients who get hurt are overwhelmingly those with known, severe lung pathology — and the single non-negotiable rule remains that an untreated pneumothorax means no chamber, full stop.
Frequently Asked Questions
Can someone with COPD get hyperbaric oxygen therapy at all?
Often yes, but it depends on severity. Mild to moderate COPD with normal blood CO2 and no large bullae is frequently treated when there's a real medical indication. Severe COPD with chronic CO2 retention or large bullous disease pushes toward caution or refusal. The decision requires a hyperbaric physician's evaluation, including an arterial blood gas test, not a quick saturation check.
What is the actual risk of a collapsed lung during HBOT?
Low. Across large reviews, pulmonary barotrauma occurs in roughly 0.0005% to 0.006% of sessions, and one three-center review found a single case in over 62,000 treatments. The risk concentrates in patients with significant known lung disease, not in those with small incidental findings. That's why the event is rare overall but still taken seriously in COPD.
Why can oxygen be dangerous for COPD when oxygen is supposed to help?
In severe COPD with chronic CO2 retention, a large oxygen load can raise blood carbon dioxide rather than lower it. The main driver is loss of the lung's protective blood-flow shunting (V/Q mismatch), with the Haldane effect adding to it. Rising CO2 can cause confusion and, at the extreme, CO2 narcosis — a serious problem inside a sealed chamber.
Do bullae or blebs automatically rule out HBOT?
No. Asymptomatic blebs and bullae are a relative contraindication, not an absolute one. Survey data show most hyperbaric centers treat patients who have lung air cysts, with very low barotrauma rates. Large, symptomatic bullous disease — especially with a prior spontaneous pneumothorax — is a much bigger concern than a small incidental lesion.
Is a low-pressure soft chamber safer for COPD than a hospital chamber?
Somewhat, but not risk-free. Lower pressure means less gas expansion on ascent, so the barotrauma risk is smaller than at 2.4 ATA, and the oxygen load is lower. But trapped air still expands, and the real danger with home soft chambers is the absence of physician screening and trained staff. A COPD patient self-treating at home skips the evaluation that makes the relative-contraindication call safe.
This article is for general education and is not medical advice. HBOT decisions for anyone with COPD or other lung disease must be made by a qualified hyperbaric physician after individual evaluation. Talk to your doctor before starting hyperbaric oxygen therapy.