Overview
1.5 ATA sits between mild HBOT and the UHMS clinical standard. It is the lowest pressure used in some hard-shell clinical chambers and appears in paediatric autism research, veterinary protocols, and conditioning phases of neurological courses. At 1.5 ATA with 100% oxygen, dissolved plasma oxygen approximately doubles compared to breathing room air at surface pressure.
1.5 ATA is a transitional pressure in the hyperbaric landscape. It is the minimum pressure used in some clinical hard-shell chamber protocols and the typical pressure of Department of Defense traumatic brain injury trials in the 2010s. Several veterinary and paediatric HBOT protocols operate at 1.5 ATA as a balance between therapeutic benefit and reduced barotrauma risk in sensitive populations.
The pressure represents approximately 7.4 psi above atmospheric. Arterial oxygen tension at 1.5 ATA with 100% oxygen is substantially higher than 1.3 ATA with 95% oxygen but lower than 2.0 ATA with 100% oxygen. The incremental dose-response of dissolved oxygen with pressure makes 1.5 ATA an intermediate point of clinical interest.
The Department of Defense trials of HBOT for military traumatic brain injury at 1.5 ATA produced mixed to negative results — a finding often cited to argue against HBOT efficacy generally. Subsequent 2.0 ATA civilian trials have shown more consistent benefit, suggesting that 1.5 ATA may be below the therapeutic threshold for neurological HBOT.
How It Works
Chamber pressurised to 1.5 ATA (about 7.4 psi above atmospheric) using either 100% medical oxygen (hard-shell monoplace) or air with mask oxygen delivery (multiplace). Session length typically 60–90 minutes. Compression and decompression windows are 5–10 minutes each. Lower pressure reduces barotrauma risk compared to clinical standards.
Protocol Parameters
| Pressure | 1.5 ATA (≈ 7.4 psi above atmospheric) |
|---|---|
| Session length | 60–90 minutes |
| Frequency | 5 sessions/week |
| Typical course | 40 sessions |
Indications
- Paediatric protocols (autism research)
- Veterinary HBOT
- Introductory sessions for pressure-sensitive patients
- Department of Defense TBI protocols
1.5 ATA is used in specific research and veterinary applications. Not sufficient for UHMS-approved emergency indications. The DoD TBI trials at this pressure have produced mixed results.
Evidence Base
Rossignol et al. (2009) autism RCT at 1.3 ATA; subsequent 1.5 ATA studies have shown mixed results. Veterinary case literature supports wound and recovery use. DoD BIMA trials failed to show benefit at 1.5 ATA for TBI.
Cautions & Notes
- Insufficient for emergency UHMS indications
- Verify chamber certification for medical use at this pressure
- Pressure may be below therapeutic threshold for neurological indications
- Mixed results in TBI trials at this pressure
Practical Considerations
1.5 ATA is a reasonable intermediate pressure for pressure-sensitive patients (paediatric, elderly with ear equalisation challenges, patients with mild cardiopulmonary disease). For neurological indications, 2.0 ATA has stronger evidence. For emergency indications, higher pressures are required.
Frequently Asked Questions
Why does the DoD use 1.5 ATA?
The DoD BIMA (Brain Injury and Mechanisms of Action of HBOT) programme used 1.5 ATA based on earlier Harch-group work. Subsequent 2.0 ATA Efrati Lab trials have shown stronger results, suggesting pressure matters.
Is 1.5 ATA real HBOT?
Yes — 1.5 ATA with 100% oxygen in a hard-shell chamber is medical HBOT at a lower pressure. Whether it is sufficient for a given indication depends on the indication and emerging evidence.
Who delivers 1.5 ATA treatment?
Some hard-shell clinical facilities offer 1.5 ATA for pressure-sensitive patients. Compact portable hard-shell home units often support this pressure. Veterinary HBOT frequently uses 1.5 ATA for small animals.
Research disclaimer: This protocol summary is for educational purposes only. HBOT is a regulated medical treatment that must be administered under appropriate professional supervision. Always consult a qualified physician before initiating hyperbaric therapy.