Overview
2.4 ATA (sometimes rounded to 2.5 ATA) is the Undersea and Hyperbaric Medical Society-recommended treatment depth for most of the 14 UHMS-approved indications, including diabetic foot ulcers, radiation tissue injury, and compromised skin grafts. Insurance reimbursement in the US is generally tied to this pressure. Sessions typically run 90–120 minutes with internal air breaks to reduce oxygen toxicity risk.
2.4 ATA is the clinical workhorse pressure of medical HBOT in the US. Nearly every UHMS-approved wound-care indication is treated at this pressure, and CMS/Medicare reimbursement documentation requirements are built around 2.4 ATA protocols. The pressure sits at approximately 20.6 psi above atmospheric — about 54 feet of seawater equivalent.
The clinical evidence at 2.4 ATA is deep. Decades of case series, retrospective analyses, and some RCTs support the pressure for diabetic foot ulcer healing (Löndahl 2010 used 2.5 ATA, Faglia 1996 used 2.2–2.5 ATA), delayed radiation injury (Marx 1985 protocol), compromised grafts, and chronic refractory osteomyelitis. The Marx protocol for dental extractions in irradiated jaws (20 pre-op + 10 post-op sessions) is the paradigm example of a 2.4 ATA prophylactic application.
Barotrauma risk is higher at 2.4 ATA than at 2.0 ATA, making ear equalisation screening particularly important. Oxygen toxicity risk is mitigated by scheduled 5-minute air breaks every 20–30 minutes during the oxygen-breathing phase. CNS oxygen toxicity seizures are rare (~1 in 10,000 sessions) with proper protocols.
How It Works
Chamber pressurised to 2.4 ATA (approximately 20.6 psi above atmospheric). Hard-shell monoplace with 100% medical oxygen or multiplace with air + mask oxygen delivery. Compression 10–15 minutes, 90–120 minutes at depth with air breaks every 20–30 minutes, 10–15 minute decompression. Total session 90–120 minutes.
Protocol Parameters
| Pressure | 2.4 ATA (≈ 20.6 psi above atmospheric) |
|---|---|
| Session length | 90–120 minutes with 5-min air breaks every 30 min |
| Frequency | 5 days/week (daily) |
| Typical course | 20–40 sessions (indication-dependent) |
Indications
- Diabetic foot ulcers (Wagner Grade 3+)
- Delayed radiation injury (soft tissue + osteoradionecrosis)
- Compromised skin grafts/flaps
- Chronic refractory osteomyelitis
- Necrotising soft-tissue infections (adjunctive)
2.4 ATA is the UHMS-recommended pressure for most of the 14 approved indications. The pressure is specifically tied to CMS/Medicare reimbursement; off-label use is at this pressure less commonly than at 2.0 ATA.
Evidence Base
Decades of clinical evidence; most UHMS indications ratified at or near this pressure. CMS reimbursement eligible. Multiple RCTs (Löndahl 2010, Clarke 2008) and the Marx 1985 protocol establish the clinical standard.
2.4 ATA UHMS protocols have the longest clinical evidence base in hyperbaric medicine. This is the "classical" HBOT pressure for wound care and radiation injury. Clinical response is well-characterised, and documentation requirements for CMS reimbursement are standardised.
Cautions & Notes
- Barotrauma risk higher than 2.0 ATA — ear equalisation screening required
- Oxygen toxicity risk mitigated by air breaks
- Daily attendance for 20–40 session courses
- Specific documentation requirements for CMS reimbursement
Practical Considerations
2.4 ATA is the pressure clinically delivered at most UHMS-accredited hospital hyperbaric facilities for wound-care indications. Patients should expect daily sessions over 4–8 weeks, with pre-treatment screening (ear equalisation, chest imaging, cardiovascular review) before the course begins.
Frequently Asked Questions
Why 2.4 ATA rather than a round number?
The pressure corresponds to 45 feet of seawater equivalent — a convention from the US Navy diving tables. Clinical protocols adopted this depth as a balance between therapeutic oxygen delivery and tolerability. Some facilities round to 2.5 ATA with equivalent clinical outcomes.
What indications are treated at 2.4 ATA?
Most UHMS-approved indications except for emergency indications (CO poisoning, DCS, gas gangrene) which use higher pressures. Diabetic foot ulcers, radiation injury, compromised grafts, chronic osteomyelitis, and sudden hearing loss are the primary 2.4 ATA indications.
Is 2.4 ATA safe for older adults?
Yes, with appropriate screening. Cardiac evaluation and ear equalisation assessment are particularly important in older patients. Barotrauma risk is manageable with proper equalisation technique and compression rate.
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.