- The AOA UHM written exam has four domains: Fundamentals (40%), Diving medicine (30.5%), Clinical hyperbaric medicine (26.5%), Research (3%).
- The exam is 150 multiple-choice questions; a scaled score of 500 (on a 200-800 scale) is passing.
- Fundamentals and Diving medicine together account for over 70% of the exam - prioritize them first.
- Application requires documentation of supervision across 13 treatment indications, totaling at least 500 treatments.
Exam Blueprint Overview
Candidates preparing for AOA Subspecialty Certification in Undersea and Hyperbaric Medicine often assume the exam is weighted evenly across clinical topics. It isn't. The American Osteopathic Conjoint Undersea & Hyperbaric Medicine Examination Committee publishes a four-category outline for its written examination, and the weighting is lopsided by design: two domains carry roughly 70% of the scored content, while a third domain sits at single-digit weight. Understanding this distribution before you build a study plan is the single highest-leverage decision you can make.
This guide breaks down each of the four content areas - Fundamentals, Diving medicine, Clinical hyperbaric medicine, and Research - so you know exactly what to study, in what proportion, and why. If you haven't yet reviewed the broader mechanics of the credential, our UHM Requirements guide and UHM Certification overview are good companion reads before you dive into domain-level prep.
Domain 1: Fundamentals (40%)
Fundamentals is the largest single content area on the exam, and its size reflects how much of hyperbaric practice depends on baseline physiology and physics rather than disease-specific protocols. This domain is where the exam tests whether you actually understand the "why" behind hyperbaric oxygen therapy, not just the "what."
Fundamentals
Candidates must demonstrate mastery of the physical and physiological principles that govern how compressed gas and increased barometric pressure interact with human tissue.
- Gas laws (Boyle's, Dalton's, Henry's) as applied to chamber operations and tissue oxygenation
- Oxygen transport, hyperoxia, and vasoconstriction effects at pressure
- Chamber equipment, safety systems, and fire-risk management
- Physiologic effects of pressure on the ear, sinuses, lungs, and central nervous system
- Oxygen toxicity thresholds and monitoring during treatment
Because Fundamentals touches nearly every other domain indirectly, weak preparation here tends to erode scores on Diving medicine and Clinical hyperbaric medicine questions as well. Treat this as your foundation layer, not a topic you review once and move past.
Domain 2: Diving Medicine (30.5%)
Diving medicine is the second-largest domain and the area most likely to surprise candidates who come from a purely clinical hyperbaric-medicine background without occupational or recreational diving exposure. Nearly a third of the exam draws from this content area.
Diving Medicine
This domain evaluates knowledge of decompression physiology, dive-related injury, and fitness-to-dive determinations - topics that overlap with but are distinct from clinical chamber therapy.
- Decompression sickness pathophysiology, classification, and emergency management
- Arterial gas embolism recognition and treatment sequencing
- Barotrauma of the ear, sinus, lung, and dental structures
- Diving fitness evaluations and medical contraindications to diving
- Commercial, military, and recreational diving physiology differences
Key Takeaway
If your clinical background is hospital-based hyperbarics without direct diving-medicine exposure, allocate extra study time here - this domain rewards dedicated review, not passive familiarity.
Domain 3: Clinical Hyperbaric Medicine (26.5%)
Clinical hyperbaric medicine is the domain most closely tied to day-to-day practice for physicians already working in wound-care or hyperbaric-medicine settings. It carries just over a quarter of the total exam weight and centers on the approved and evidence-supported indications for hyperbaric oxygen therapy.
Clinical Hyperbaric Medicine
This domain tests recognition of treatable conditions, dosing protocols, and complication management within a hyperbaric chamber setting.
- Approved treatment indications and appropriate patient selection
- Treatment protocols, pressure schedules, and number-of-treatment guidance
- Wound healing physiology and adjunctive therapy decisions
- Complication recognition - oxygen toxicity seizures, barotrauma, confinement anxiety
- Contraindications and relative-risk patient populations
Notably, the application process itself reinforces this domain's real-world weight: candidates must document supervision of at least 500 treatments distributed across the 13 treatment indications specified in the published eligibility requirements. If you've logged that case volume honestly across varied indications, much of this domain will already feel familiar by exam day.
Domain 4: Research (3%)
Research is the smallest domain by a wide margin, accounting for just 3% of the exam. Candidates sometimes over-invest here out of anxiety about the unfamiliar, but the proportional weight tells you how to allocate your limited study hours.
Research
This domain covers the interpretation and application of hyperbaric-medicine literature rather than the conduct of original research.
- Levels of evidence and study design recognition
- Interpreting outcomes data for hyperbaric oxygen therapy indications
- Understanding how evidence quality informs indication approval
Mapping the Weights to a Study Schedule
You don't need an elaborate system to study effectively for this exam - you need a schedule that mirrors the blueprint. A simple, weighted rotation works better than generic daily study blocks because it forces proportional time-on-task.
Fundamentals (40%)
- Gas laws, oxygen transport, and chamber physics
- Complete practice questions focused on physiologic mechanisms
Diving Medicine (30.5%)
- Decompression sickness and arterial gas embolism protocols
- Barotrauma and fitness-to-dive scenarios
Clinical Hyperbaric Medicine (26.5%)
- Review approved indications and treatment protocols
- Cross-reference your logged treatment cases against the 13 indications
Research (3%) + Full Review
- Light review of evidence levels and study design
- Mixed-domain practice exams weighted to match the real blueprint
For a more detailed week-by-week breakdown and pacing strategy, see our full UHM Study Guide 2026: How to Pass on Your First Attempt. And if you're still calibrating how much total effort this exam requires relative to your background, How Hard Is the UHM Exam? Complete Difficulty Guide 2026 walks through that in more depth.
Registration, Fees, and Eligibility Mechanics
Domain preparation doesn't happen in a vacuum - it's built on top of the eligibility pathway you've already completed. Before you can sit for the written exam, published eligibility requires a COCA-accredited osteopathic medical degree, a one-year AOA-approved internship, a one-year AOA- or ACGME-approved hyperbaric medicine fellowship, and primary certification through AOBEM, AOBFP, AOBIM, or AOBPM, along with unrestricted medical licensure and ethical standing.
The application itself requires a CV, license documentation, fellowship verification, and - critically for Clinical hyperbaric medicine domain readiness - documentation of supervised treatments spanning the 13 specified treatment indications, totaling at least 500 treatments.
| Item | Detail |
|---|---|
| Exam format | 150 multiple-choice questions |
| Passing standard | Scaled score of 500+ (200-800 scale) |
| Exam fee | $1,100 |
| Recertification fee | $1,100 |
| Recertification cycle | 10-year cycle via written OCC assessment |
| Additional CME | None beyond primary-board CME and OCC compliance |
For a full cost breakdown across the whole certification lifecycle, see UHM Certification Cost 2026: Complete Pricing Breakdown. If you want the exact scoring mechanics explained in isolation, UHM Passing Score 2026: Exactly What You Need to Pass covers the 500-point scaled threshold in detail. Note also that the official written-exam page still displays older scheduling text from 2024, so don't assume that date applies to a 2026 administration - confirm current windows directly with the AOA conjoint committee or check UHM Exam Dates 2026: Testing Windows, Deadlines & Scheduling for the latest guidance.
Who Actually Hires for This Skill Set
The domains above map directly onto how hyperbaric medicine programs staff their teams. Hospital-based wound care and hyperbaric centers look for physicians who can independently manage the Clinical hyperbaric medicine caseload - approving indications, writing treatment protocols, and recognizing complications in real time. Dive-medicine consultative roles, occupational health programs serving commercial divers, and military-adjacent civilian contract positions weight the Diving medicine domain much more heavily in day-to-day work.
Because Fundamentals underlies both settings, physicians who test well in that domain tend to transition more easily between hospital-based and diving-medicine-focused roles. If you're evaluating whether this credential fits your career trajectory, UHM Jobs and UHM Salary Guide 2026: Complete Earnings Analysis go deeper on where this certification opens doors, and Is the UHM Certification Worth It? Complete ROI Analysis 2026 weighs the investment against long-term practice options.
Key Takeaway
Study Diving medicine even if your current job is hospital-based - it's nearly a third of the exam and often the least-practiced domain for chamber-only clinicians.
Turning Domain Knowledge Into Exam-Day Performance
Once you've built content knowledge across all four domains, the remaining gap is usually question-format familiarity. Running full-length practice sets that mirror the real 40/30.5/26.5/3 weighting - rather than generic hyperbaric-medicine quizzes pulled from unrelated sources - gives you a more honest read on where you stand. You can build that kind of weighted practice routine using our practice test platform, which lets you drill each domain in proportion to its actual exam weight rather than guessing at emphasis.
If you're just getting oriented to the credential itself before committing to a study plan, our foundational explainers - What Is UHM?, UHM Meaning, and What Is UHM Certification? - are useful starting points, as is UHM Training for background on the fellowship pathway that precedes eligibility. When you're ready to check where your baseline knowledge stands, start with a diagnostic practice run before committing to a six-week schedule.
Frequently Asked Questions
Start with Fundamentals. At 40% of the exam, it's the largest domain and its physiology and physics concepts underpin questions in both Diving medicine and Clinical hyperbaric medicine.
No. Research accounts for only 3% of the exam. A brief review of evidence levels and study interpretation is sufficient - don't let it crowd out time for the two largest domains.
Yes, particularly for Clinical hyperbaric medicine. The eligibility requirement to document supervision of at least 500 treatments across 13 treatment indications naturally builds familiarity with much of that domain's content.
The written exam contains 150 multiple-choice questions, and passing requires a scaled score of at least 500 on a 200-800 scale.
No. This guide covers the AOA initial written examination administered by the American Osteopathic Conjoint Undersea & Hyperbaric Medicine Examination Committee, which follows AOBEM, AOBFP, AOBIM, or AOBPM primary certification - a distinct pathway from the separate ABPM/ABEM examination.