What Does CHRN Stand For?

The Short Answer: Certified Hyperbaric Registered Nurse

On this site, CHRN stands for Certified Hyperbaric Registered Nurse. It is the credential held by registered nurses who have demonstrated competence in caring for patients undergoing hyperbaric oxygen therapy and who understand the physics, physiology, equipment, and safety demands of the hyperbaric environment.

The acronym is shared by other, unrelated credentials in other fields, so it is worth being precise. Everything on CHRN Exam Prep concerns the nursing certification for hyperbaric medicine and nothing else. If you want the broader picture beyond the acronym itself, our overview articles What Is CHRN? and CHRN Certification walk through the credential from different angles, and the CHRN practice test lets you check your readiness against the format.

Reading the Credential Word by Word

Each word in the title tells you something concrete about who qualifies and what the credential covers.

Certified

The nurse has passed a standardized examination and met documented eligibility requirements. This is not an attendance certificate from a training course. The 40-hour introductory course is a prerequisite for testing, not a substitute for it. See CHRN Training for how the course fits into the pathway.

Hyperbaric

The clinical setting is the pressurized chamber environment. Candidates are expected to understand how elevated ambient pressure affects gas-filled spaces, equipment, vascular access lines, and the patient's physiology, and how oxygen delivered above one atmosphere absolute produces therapeutic effects.

Registered Nurse

Only licensed RNs qualify. An unrestricted RN license is required to apply and to renew. This is what separates the CHRN from technologist-level credentials, which brings us to a distinction covered later in this article.

Who Stands Behind the Credential

Two organizations share the work, and candidates often confuse their roles.

In practice, this means your application is evaluated against nursing-specific eligibility rules, while the examination itself is run through NBDHMT's testing process. The exam is delivered at a designated testing site. It is not default unproctored home testing, and any in-house proctorship requires NBDHMT approval.

What the Title Implies About the Exam

The name suggests a nursing exam, but the content is broader than bedside nursing alone. The published CHRN study guide blends nursing management with physics, decompression theory, chamber operations, and fire safety. The nursing program page describes a nursing-versus-technical balance when recounting the exam's early-1990s design, but that historical description is not a current weighted blueprint, and no official percentage weights are verified for today's exam.

What is established about the format:

• 120 questions, multiple-choice and true/false
• Two hours to complete the exam
• 70% passing threshold
• No essay or short-answer items
• Dive tables are supplied, and a pocket calculator is allowed

The split between scored and unscored items, and whether the exam is adaptive, are not established in the available sources. For score mechanics, see CHRN Passing Score, and for the honest state of the data on outcomes, read CHRN Pass Rate. A credential-specific pass rate is not publicly disclosed.

The Sixteen Preparation Areas Behind the Name

The June 2024 Resource Manual's study-guide contents list sixteen technical preparation topics. These are issuer study-guide competencies, not an officially weighted exam blueprint, so treat them as a map of scope rather than a percentage breakdown. Our CHRN exam domains guide covers each in detail. Here is how they group.

What It Takes to Earn the Letters

The word "Certified" is earned through a layered set of prerequisites. The full list lives in CHRN Requirements, but the core elements are:

• An unrestricted RN license
• Two years of hospital or clinic experience, or one year of critical care
• A recent active year of hyperbaric experience
• An approved 40-hour introductory course, or applicable 40 Category A replacement credits
• 480 post-course patient-care hours
• Approval from a qualified preceptor and a recommendation from your employer

Registration and fees

The June 2026 initial application confirms the following examination fees, with membership evidence required for the discounted tiers. The application advises registering 30 days before the test.

The June 2024 manual lists US$100 for a repeat examination, and no newer retake-fee override was found. For the full cost picture across initial testing, renewal, and lapse, see CHRN Certification Cost, and for timing, CHRN Exam Dates.

Keeping the Letters: Renewal Every Four Years

"Certified" is not permanent. The credential renews every four years. Per the August 2025 renewal form, you need:

• An active RN license
• Employer or medical-director confirmation of at least one year of hyperbaric experience, including 480 hours within the previous 12 months
• 40 CE hours over four years, including 20 Category A hours

Renewal fees are US$150 for BNA members, US$200 for UHMS or ACHM members, and US$250 for nonmembers. A lapse adds US$100 and removes member discounts. Note that the older manual's statement that ongoing hours need not be logged does not waive the newer form's employer-validated recent-practice requirement.

Related Abbreviations You Will See in CHRN Materials

CHRN documents use several neighboring abbreviations. A few clarifications prevent confusion:

• CHT in CHRN documents means Certified Hyperbaric Technologist, a separate technologist credential. It does not refer to any hospitality-training certification of the same letters.
• BNA is the Baromedical Nurses Association, the professional body for hyperbaric nurses.
• UHMS is the Undersea and Hyperbaric Medical Society, whose accepted-indications list underpins Domain 6.
• NFPA refers to the fire-safety guidance that applies to hyperbaric chambers.
• TcPO2 is transcutaneous oxygen monitoring, a wound-assessment tool covered in Domain 13.

This article addresses the basic Certified Hyperbaric Registered Nurse certification. Other nursing-related credentials and administrative renewal pathways are separate topics and are not covered here. For alternative phrasings of the same question, our pages on CHRN meaning and what a CHRN is cover the ground from the job-role side.

Where the Credential Is Used

Certified Hyperbaric Registered Nurses work where hyperbaric oxygen therapy is delivered: hospital-based hyperbaric departments, wound care and hyperbaric centers, and outpatient clinics that operate monoplace or multiplace chambers. Because the exam pulls from wound healing, critical care, pediatric considerations, and pharmacology in the hyperbaric environment, nurses with wound care, critical care, or emergency backgrounds often find the clinical content familiar, while the physics and decompression content tends to be the steeper climb.

For a look at roles and employers, see CHRN Jobs. For compensation and whether the effort pays off, CHRN Salary Guide and Is the CHRN Certification Worth It? take a careful, evidence-based look rather than offering unsupported figures.

Using the Name to Organize Your Preparation

The three words in the title suggest a sensible order of attack: lean on what you already know as a registered nurse, then build the hyperbaric knowledge that makes the credential distinct. A simple sequence tied to the sixteen areas:

For a fuller plan, read the CHRN Study Guide, and for a compressed refresher the week before testing, use the CHRN Cheat Sheet. If you are weighing your readiness, How Hard Is the CHRN Exam? gives a realistic view of where candidates tend to struggle. When you are ready to test yourself, the practice questions at CHRN Exam Prep are built around the same sixteen-area scope. Our other explainer pages, including What Is CHRN Certification? and What Does CHRN Mean?, answer variations of this same naming question.

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