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What is your role in hyperbaric medicine safety?  Are you a Technologist, Nurse, Safety or Medical Director?  In any of these roles, you will need to address prohibited items during hyperbaric oxygen therapy.  

Prohibited items… the risk assessment and approval or denial are topics that continually persist.

It is “kicking the dead horse” that may or may not be dead.  

In other words, this process is never ending. 

The NFPA 99 2021 edition, chapter 14 Hyperbaric Facilities – provides the process for effectively managing patient care product(s) during hyperbaric oxygen therapy.  The NFPA 99 2021 edition - states “Physician and Safety Director approval to use prohibited items shall be stated in writing for all prohibited materials employed”

What is your process? Is it collaborative between the Medical Director and the Safety Director? The intent for requiring both physician (Medical Director) and Safety Director approval is to ensure that a thorough Risk Assessment be performed and that there is no conflict(s) of interest putting the patient at risk.  The following is a condensed review of the NFPA 99 2021:

General Risk Assessment: 

Evaluation of wound dressings for use in the hyperbaric chamber

The NFPA 99 provides with an algorithm (see Figure A. of the NFPA 99 2021, transcribed below) as a visual means for evaluation of products for use in the hyperbaric chamber.  It was originally designed to evaluate wound dressing products for use in a hyperbaric chamber. However, the risk assessment process is a valuable tool and the same decision process should be used for all that have not been evaluated or deemed safe for use in the hyperbaric chamber. Unfortunately, the aforementioned risk assessment tool does not provide a means for documentation of the risk assessment.   A. (7) of the NFPA 99 2021 states:

"The hyperbaric facility should maintain a “use list” and a “do not use list” of items that have been evaluated for hyperbaric use. In addition to this list, it is important to keep documentation on file explaining the risk assessment for each item. This will prevent future duplication of effort. It also serves as evidence that due diligence was used.

It was this statement that motivated the WoundReference team to develop the Go-No-Go Assessment Tool.  The  Go-No-Go Risk Assessment Tool is an interactive tool that  facilitates the decision-making and documentation process. The Tool enables HBOT clinicians to assess the risk for each area of concern (production of heat, static, flash point, fuel load, adverse effect, mechanical), quantify each risk with a score and more confidently determine the risk level of each itemUpon completion of the risk assessment process, HBOT clinicians can print or email the document and upload documentation to the electronic medical record. The Tool allows each facility to have a digital, customized "Go-No Go" list, that can be accessed by the entire team.

Important safety concerns include the production of heat, production of static electricity, production of flammable vapor, ignition temperature, and total fuel load. Many wound dressings employ fabrics and other materials that are gas-permeable. It is a common misconception that a gauze bandage will isolate an undesirable product from the chamber environment. Gauze is gas permeable and will allow oxygen from the chamber to interact with the product and vapors from the product to interact with the chamber environment. Also, gas-permeable materials exposed to hyperbaric oxygen will hold additional oxygen for some period of time after the exposure. These materials should be kept away from open flames for at least 20 minutes after the hyperbaric treatment.

A. - The textiles definitions and risk assessment process for hyperbaric wound dressings are as follows:

  • Combustion - A chemical process of oxidation that occurs at a rate fast enough to produce heat in the form of either a glow or a flame.
  • Flammable - Refers to a combustible (solid, liquid, or gas) that is capable of easily being ignited and rapidly consumed by fire.
  • Flash Point -The minimum temperature of a liquid or solid at which it gives off vapor sufficient to form an ignitible mixture with oxygen under specified environmental conditions.
  • Ignition Temperature - The minimum temperature required to initiate or cause self-sustaining combustion under specified environmental conditions.
  • Lower Explosive Limit (LEL) or Lower Flammable Limit (LFL) - The minimum concentration of fuel vapor (percent by volume) over which combustion will occur on contact with an ignition source.
  • Risk Assessment Process diagram (see Figure A. of the NFPA 99 2021, transcribed below):

As you run through the risk assessment process, you should be thinking about the following questions, as illustrated in the diagram above. 

(1) Is there a more suitable alternative to this dressing?

The issue of need must first be addressed. There might be a substitute dressing that has already been deemed acceptable for the hyperbaric environment. Can the wound dressing orders can be changed to the more desirable substitute Is it viable to remove the dressing before the hyperbaric treatment, leave it off during the treatment, and  replace it after the treatment?

(2) Does this dressing produce heat in the chamber?

Dressings are made from a large variety of materials. The concern is that materials in a dressing can rapidly oxidize and produce heat (exothermic reaction) when exposed to additional oxygen. For example, air-activated heat patches (commonly used for pain relief) have been tested in hyperbaric environments. The average operating temperature increased from 48.1°C (119°F) in normobaric air to 121.8°C (251°F) in hyperbaric oxygen. In this circumstance, the patient’s skin would be burned, and the heat could ignite combustible material in the chamber.  

(3) Does this dressing produce too much static electricity?

All common textiles will contribute to static production. Wool and synthetic materials generally contribute more to static production than cotton. Although static charge is constantly accumulating, it will dissipate into the environment when humidity is present. At less than 30% relative humidity, static charge can accumulate faster than it can dissipate. At greater than 60% relative humidity, static charge is all but completely eliminated. Use of  conductive surfaces and electrical grounding will allow static charge to dissipate.

(4) Does this dressing have a low ignition temperature/flashpoint?

In all hyperbaric environments, the partial pressure of oxygen is higher than at normal atmospheric conditions. Increasing the partial pressure of oxygen can change the classification of a material from nonflammable to flammable. Many materials are flammable in a 100 percent oxygen environment. Any material used in a hyperbaric chamber should have an ignition temperature higher than it can be exposed to.

  • Paragraph of the NFPA 99 2021 limits electrical circuits inside a Class B (monoplace) chamber to a maximum operating temperature of 50°C (122°F).  As the oxygen percentage increases, it takes less energy to ignite  materials. This leads to more conservative decisions in a 100 percent oxygen environment.. A material will release vapor into the chamber environment as it approaches its flash point temperature. Once a sufficient quantity of vapor is present in the chamber (LEL), it takes very little energy for ignition to occur.
  • Paragraph of the NFPA 99 2021 specifically prohibits flammable liquids, gases, and vapors inside Class B chambers.  Information on ignition temperature and flash point in air can be found in a product MSDS.

(5) Is the total fuel load too high?

If a fire does occur, the energy produced is a function of the partial pressure of oxygen and the total fuel load.  Any dressing product placed inside of a hyperbaric chamber is a combustible material and, therefore, adds to  the fuel load. Therefore, total fuel load inside the chamber should be minimized to only what is necessary.

(6) Is there an adverse effect when this product is used inside the hyperbaric chamber?

It has been reported that the antibacterial agent mafenide acetate (Sulfamylon®), in combination with hyperbaric oxygen, has a poorer clinical result than either one by itself. There can be other drug interactions with hyperbaric oxygen that are undesirable.

(7) Are there “use/do not use lists” and documentation readily available? 

The hyperbaric facility should maintain a “use list” and a “do not use list” of items that have been evaluated for hyperbaric use. In addition to this list, it is important to keep documentation on file explaining the risk assessment for each item. This will prevent future duplication of effort. It also serves as evidence that due diligence was used.  

For your convenience, WoundReference maintains a comprehensive, growing list of items that are approved for use, should be used with caution and should not be used in the chamber. (See Go-No-Go Lists / Prohibited Items). An authorization form is required for items that should be used with caution (see Figure below).



We thank Julie Rhee ScM, for style editing

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