Breathing oxygen under pressure. A proven hospital treatment for specific conditions like decompression sickness; home soft chambers aren't that, and longevity use is unproven.
Hyperbaric oxygen therapy (HBOT) means breathing close to 100% oxygen while the pressure around you is raised, usually to 2–3 times normal atmospheric pressure, in a hospital-grade chamber. That drives far more oxygen into your blood, and it's an established treatment for a short list of conditions, from decompression sickness to carbon monoxide poisoning and some non-healing wounds.
Most chambers sold for homes and wellness clinics are different. Soft-sided 'mild' chambers reach about 1.3 atmospheres, usually with ordinary air or oxygen from a concentrator. Breathing air at 1.3 atmospheres raises your oxygen intake only about as much as a little supplemental oxygen at sea level, a small fraction of a clinical dose. In the US, soft chambers have been cleared for acute mountain sickness, not for wellness or anti-ageing.
In hospitals, recompression with oxygen is the standard treatment for decompression sickness and gas embolism, and the US FDA has cleared hyperbaric chambers for about a dozen specific conditions. Even there, trial evidence varies: a Cochrane review found diabetic foot ulcers healed faster at six weeks but not at one year. For healthy people, the widely cited 'anti-ageing' study had 35 older adults, no control group, and measured telomeres in blood cells rather than ageing itself. Home soft chambers deliver a much smaller dose and have no outcome trials for wellness uses.
Reviews decompression illness in divers, aviators and others: first aid is 100% oxygen, definitive treatment is recompression breathing 100% oxygen, and treatment is usually effective, though serious cases can leave lasting deficits.
In 152 patients with symptomatic carbon monoxide poisoning, three hyperbaric oxygen sessions within 24 hours reduced cognitive problems at six weeks (25% vs 46% with normal-pressure oxygen), with a benefit still seen at 12 months.
Across 12 trials (577 people), HBOT improved healing of diabetic foot ulcers at six weeks (RR 2.35) but not at one year, with no significant difference in major amputations; trial flaws limited confidence.
Thirty-five healthy adults aged 64 and over received 60 daily HBOT sessions; telomere length in several blood immune-cell types rose by more than 20% and some senescent T-cell counts fell. There was no control group, and no clinical outcomes were measured.