HBOT at 2 ATA: Why Clinical-Grade Pressure Matters

Hyperbaric oxygen therapy (HBOT) involves breathing pure or near-pure oxygen in a pressurised chamber at levels above normal atmospheric pressure. Whilst the concept is straightforward, the clinical outcomes of HBOT depend heavily on one critical variable: the pressure at which treatment is delivered. Not all hyperbaric chambers are equal, and not all pressures produce the same physiological effects. This article explains why 2 ATA (atmospheres absolute) represents the clinical standard for therapeutic HBOT and what distinguishes medical-grade treatment from lower-pressure alternatives.

What Does 2 ATA Mean?

Atmospheric pressure at sea level is defined as 1 ATA. When a hyperbaric chamber is pressurised to 2 ATA, the total pressure inside the chamber is twice normal atmospheric pressure. This is equivalent to the pressure experienced at approximately 10 metres of seawater depth.

The “absolute” in ATA is significant. It refers to total pressure, including the baseline atmospheric pressure. A chamber operating at 2 ATA therefore applies 1 additional atmosphere of pressure above ambient conditions. This distinction matters because the biological effects of HBOT are directly proportional to the absolute pressure achieved.

At 2 ATA, breathing 100% oxygen results in an arterial oxygen partial pressure (PaO2) of approximately 1,400 mmHg, compared to roughly 100 mmHg under normal breathing conditions. This represents a more than tenfold increase in dissolved oxygen availability, a level that triggers significant physiological responses in tissue oxygenation, cellular signalling, and immune function.

Hard Shell vs Soft Shell Chambers

The type of chamber used for HBOT determines the maximum pressure that can be achieved and, consequently, the therapeutic potential of the treatment.

Hard Shell Chambers

Hard shell chambers are medical-grade devices constructed from steel or acrylic and engineered to withstand pressures of 2 ATA and above. They come in two configurations:

Monoplace chambers accommodate a single patient and are typically pressurised with 100% oxygen. The patient lies inside a transparent acrylic cylinder, allowing visual contact with clinical staff throughout the session.

Multiplace chambers accommodate multiple patients simultaneously. These larger chambers are pressurised with compressed air, and patients breathe pure oxygen through a mask or hood system known as a Built-In Breathing System (BIBS).

Both configurations are capable of achieving the 2 ATA pressure required for clinical-grade HBOT. At Longevity Thailand, treatment is delivered using a medical-grade hard shell chamber that meets international safety and performance standards.

Soft Shell Chambers

Soft shell (or mild) hyperbaric chambers are portable, inflatable devices that have become widely available for home and wellness use. These chambers typically reach a maximum pressure of 1.3 ATA and use ambient air or oxygen concentrators rather than pure medical-grade oxygen.

The clinical significance of this pressure difference is substantial. At 1.3 ATA with ambient air (21% oxygen), the increase in dissolved plasma oxygen is modest compared to what is achieved at 2 ATA with near-pure oxygen. The published clinical evidence supporting HBOT for wound healing, neurological rehabilitation, and inflammatory conditions is based on protocols using hard shell chambers at pressures of 1.5 to 2.4 ATA, not the 1.3 ATA achievable in soft shell devices.

This does not mean that mild hyperbaric exposure has no effect. Some preliminary research suggests potential benefits at lower pressures for specific applications. However, patients seeking evidence-based clinical outcomes should understand the distinction between these two categories of device.

The Science of Oxygen Under Pressure

The therapeutic mechanism of HBOT is grounded in well-established physics, specifically Henry’s Law, which states that the amount of gas dissolved in a liquid is directly proportional to the partial pressure of that gas above the liquid.

Under normal conditions, oxygen is transported in the blood primarily by haemoglobin within red blood cells. Haemoglobin is approximately 97% saturated with oxygen under normal breathing conditions, leaving very little room for additional oxygen transport via this mechanism.

However, a small but physiologically significant amount of oxygen is also dissolved directly in the blood plasma. Under normal conditions, plasma carries approximately 0.3 mL of dissolved oxygen per 100 mL of blood. At 2 ATA breathing 100% oxygen, this figure rises to approximately 4.4 mL per 100 mL, an increase of more than tenfold.

This plasma-dissolved oxygen is critically important because it is not dependent on haemoglobin for delivery. It can reach tissues that have compromised blood supply, areas of swelling, or regions where red blood cells cannot penetrate efficiently. This is why HBOT is particularly valuable in conditions involving ischaemia, oedema, or impaired microcirculation.

The elevated oxygen levels achieved at 2 ATA also trigger several secondary biological responses:

Neovascularisation: Repeated exposure to hyperbaric oxygen stimulates the growth of new blood vessels in oxygen-deprived tissues, a process known as angiogenesis. This effect persists beyond the treatment session and contributes to long-term tissue recovery.

Stem cell mobilisation: Research published in the American Journal of Physiology has demonstrated that HBOT at therapeutic pressures can mobilise stem and progenitor cells from the bone marrow into the peripheral circulation, potentially supporting tissue repair processes throughout the body.

Anti-inflammatory signalling: Hyperbaric oxygen modulates inflammatory pathways, including the reduction of pro-inflammatory cytokines and the promotion of anti-inflammatory mediators. This dual action helps resolve chronic inflammation whilst supporting the constructive phase of tissue healing.

Antimicrobial effects: The elevated oxygen tension in tissues enhances the bactericidal activity of white blood cells and directly inhibits the growth of anaerobic bacteria, contributing to infection control in wound healing applications.

Oxygen Purity and BIBS Systems

Clinical-grade HBOT requires not only adequate pressure but also high-purity oxygen delivery. The oxygen used in medical hyperbaric treatment is pharmaceutical-grade, typically exceeding 93% purity.

In monoplace chambers, the entire chamber atmosphere is pressurised with pure oxygen, and the patient breathes the chamber atmosphere directly.

In multiplace chambers, a Built-In Breathing System (BIBS) is used to deliver pure oxygen to each patient via an oronasal mask or a transparent hood. The BIBS system allows patients to breathe pure oxygen whilst the chamber itself is pressurised with compressed air. This approach offers several advantages, including the ability to provide periodic “air breaks” during longer sessions. Air breaks, in which the patient temporarily breathes chamber air rather than pure oxygen, help reduce the risk of oxygen toxicity during extended treatments.

The delivery system, oxygen purity, and pressure level work together to determine the actual dose of oxygen reaching the patient’s tissues. Any compromise in one of these variables reduces the therapeutic effect. This is why clinical HBOT protocols specify all three parameters, and why treatment should be delivered in a facility with proper equipment and trained personnel.

Thai FDA Approval and Safety Protocols

Hyperbaric oxygen therapy is approved by the Thai Food and Drug Administration (Thai FDA) when delivered using certified medical devices in licensed healthcare facilities. At Longevity Thailand, HBOT is administered under full regulatory compliance, with protocols that adhere to both Thai FDA requirements and international best practice guidelines.

Safety protocols include pre-treatment medical screening to identify contraindications, continuous monitoring during sessions, and post-session assessment. Trained hyperbaric technicians operate the chamber, and a physician is available throughout the treatment period.

Contraindications

HBOT is generally well tolerated, but certain conditions represent contraindications:

Absolute contraindications include untreated pneumothorax (collapsed lung), as pressurisation could worsen this condition. Patients with this condition must not undergo HBOT until it is resolved.

Relative contraindications include uncontrolled seizure disorders, severe claustrophobia, certain pulmonary conditions such as severe COPD with air trapping, and recent ear or sinus surgery. These conditions do not necessarily preclude treatment but require careful evaluation and may necessitate protocol modifications.

All patients undergo a thorough medical assessment before commencing HBOT, including review of their medical history, current medications, and any conditions that may affect treatment safety.

Common Side Effects

The most frequently reported side effect is barotrauma to the middle ear, manifesting as a feeling of pressure or mild discomfort similar to that experienced during air travel. This is managed through equalisation techniques taught before the first session. Temporary myopia (short-sightedness) can occur after prolonged treatment courses but typically resolves within weeks of completing therapy.

Clinical Applications at 2 ATA

The clinical applications of HBOT at therapeutic pressures span several medical domains:

Wound Healing and Tissue Repair

HBOT is most extensively studied in the context of chronic and complex wounds. The increased tissue oxygenation promotes fibroblast proliferation, collagen synthesis, and angiogenesis, all essential components of the wound healing cascade. Research supports its use in diabetic foot ulcers, radiation-induced tissue injury, and compromised surgical flaps and grafts.

Chronic Inflammation

Emerging evidence suggests that HBOT can modulate chronic inflammatory conditions by reducing pro-inflammatory cytokine levels and promoting resolution of persistent inflammation. This mechanism is relevant to conditions ranging from autoimmune disorders to the chronic low-grade inflammation associated with biological ageing.

Neurological Rehabilitation

Research into HBOT for neurological conditions has expanded considerably. Studies have explored its potential in traumatic brain injury recovery, post-stroke rehabilitation, and neurodegenerative conditions. The proposed mechanisms include improved cerebral oxygenation, reduced neuroinflammation, and enhanced neuroplasticity. Whilst results are encouraging, this remains an active area of investigation.

Sports Recovery and Performance

Athletes increasingly seek HBOT for accelerated recovery from training and injury. The enhanced tissue oxygenation supports muscle repair, reduces exercise-induced inflammation, and may shorten recovery times between training sessions. Several professional sports organisations have incorporated HBOT into their recovery protocols.

Post-Surgical Recovery

HBOT before and after surgery can support tissue healing, reduce post-operative swelling, and improve outcomes in procedures involving compromised blood supply. Its use as an adjunctive therapy in surgical recovery is an area of growing clinical interest.

What a Treatment Course Looks Like

A typical HBOT treatment session at Longevity Thailand follows a structured protocol:

Pre-session preparation: The patient changes into cotton clothing (synthetic materials are not permitted in the chamber) and removes any items that could pose a safety concern. The clinical team reviews the patient’s current health status and any changes since the previous session.

Pressurisation phase: The chamber is gradually pressurised to 2 ATA over approximately 10 to 15 minutes. During this phase, patients are guided through ear equalisation techniques.

Treatment phase: Once target pressure is reached, the patient breathes pure oxygen for 60 to 90 minutes. Air breaks may be incorporated at regular intervals during longer sessions.

Depressurisation phase: The chamber is slowly returned to ambient pressure over 10 to 15 minutes. This gradual decompression minimises the risk of barotrauma.

Treatment courses typically involve 10 to 40 sessions depending on the clinical indication. Acute conditions such as sports injuries may require fewer sessions, whilst chronic conditions and longevity protocols often involve longer courses. Sessions are usually scheduled daily or five times per week, with rest days incorporated as appropriate.

Who Benefits from Clinical-Grade HBOT?

Clinical-grade HBOT at 2 ATA is relevant for a range of patient profiles:

Patients with chronic wounds or tissue injuries who have not responded adequately to conventional treatment may benefit from the enhanced tissue oxygenation and healing support that HBOT provides.

Athletes and active individuals seeking accelerated recovery from injury or intensive training often incorporate HBOT into their rehabilitation and performance programmes.

Patients undergoing regenerative medicine programmes may use HBOT as a complementary therapy alongside stem cell treatment, exosome therapy, or peptide protocols to enhance therapeutic outcomes.

Individuals pursuing longevity and anti-ageing strategies increasingly include HBOT in comprehensive wellness programmes, based on emerging research into its effects on cellular senescence, inflammation, and telomere biology.

Post-surgical patients may benefit from HBOT to support tissue healing, reduce complications, and accelerate recovery timelines.

At Longevity Thailand, HBOT is prescribed as part of an individualised treatment plan developed by our medical team. The decision to include HBOT, the number of sessions, and the integration with other therapies are all guided by clinical assessment, biomarker data, and the patient’s specific health objectives.