Intrinsically safe defibrilators

[313RN, BSN, RN]

I recently interviewed for a job in my systems hyperbaric chamber and wound care clinic. I'm an ICU nurse currently and became interested in hyperbarics as it relates to diving medicine (I was a SCUBA instructor for a time, now inactive).

They are looking for an RN with critical care experience to take ICU patients on dives from time to time.

One of the things that I asked about was how they handle codes in the chamber and if there was a defribrilator available. There was not, and the rationale (a perfectly reasonable one at that) was the increased risk of fire in an oxygen rich environment.

The thing is, if things get ugly in the chamber at depth, it can take up to 15 minutes to bring the occupants up to the surface safely (with a safety stop on 100% Fio2). That seems like a looooong time to me.

In the interview I was told that I could have whatever supplies I felt were appropriate in the chamber for emergent situations (code meds, etc).

I'd still feel better if I had a defibrilator though.

Back in another life, I was aware that there were certain electronic devices that were certified intrinsically safe and could be used safely in places where there was a high risk for fire or explosions.

I never asked about AED's then, but now that it's important to me and possibly my patients, I'm wondering:

Has anyone ever heard of an intrinsically safe AED/defirilator and if you have, do you remmeber the maker?

[MassED, BSN, RN]

interesting topic, of which I know nothing about... interested to read more!

[nurse2033, MSN, RN]

I would think it was not the defibrillator that is in question. They are extremely safe and reliable. I know from friends who "dive" that moisture and condensation can be extreme in the chamber at certain points in the dive. I would guess that the danger would be arcing from pads that are placed on wet skin. Perhaps if the pads were pre-placed on dry skin this risk could be minimized. However, even the tiniest risk of fire or explosion could be disastrous. It is a great question though.

[NP_student]

http://medind.nic.in/jab/t05/i1/jabt05i1p44.pdf

Doesn't really answer your question, but this paper states:

Electrical Defibrillation : In a hyperbaric chamber

defibrillation is controversial, because of possibility of

poor skin contact, arcing and risk of fire. Large metal

environment may predispose attendants to shock.

Chambers needs to be decompressed prior to use of a

defibrillator. Moreover the latency of bubble formation

and onset of decompression sickness symptoms is

sufficient to allow a brief excursion to 1 ATA for

defibrillation, with subsequent return to previous

pressures.

My husband is an engineer for a defibrillator manufacturer, and states that there are no AEDs intrinsically safe from arcing. However, he will verify this tomorrow...

[NP_student]

good link:

http://www.uhms.org/portals/0/Safety%20Documents/EJUHM_Vol6No4_pages_115_120.pdf

other reads:

http://www.mdsr.ecri.org/summary/detail.aspx?doc_id=8126

and

http://www.springerlink.com/content/g2t37v47u0754161/

[sharkdiver]

This is a great question!

To be clear, Oxygen is a non-flammable, non-explosive gas. It does NOT burn; however it does support combustion. Any material that will burn in air will ignite more readily in an oxygen-enriched environment. So the real problem is not so much the enriched O2, but the presence of fuel sources (combustible material) when a potential ignition source is also present.

Intrinsic safety (IS) is a Factory Mutual rating for electrical devices used in the presence or potential presence of combustible gases, vapors or dusts. An intrinsically safe electrical device is designed so that if it fails during normal use and operation it will not generate enough energy to ignite a flammable mixture of the hazardous gas or dust present. It primarily involves encapsulation of energy storage devices such as batteries and capacitors. Further, IS testing is done in a normal atmosphere of approx. 21% O2, so it does not specifically apply in atmospheres of higher concentration unless so stated.

While I haven't been able to find one certified for O2 enriched/hyperbaric chamber use, even if there were, it's not so much the defibrillator unit itself as the potential for a spark from the pads where they contact the skin of the patient. For that matter, the defibrillator unit could be outside the chamber and the leads connected via an electrical feed-through. In this event, in addition to the attendant inside the chamber, there would need to be a defibrillator operator outside. There should also be a water shower extinguisher system inside the chamber than can be immediately activated by the chamber operator in the event of a problem.

One of the studies I've seen indicates that "in a hyperbaric chamber defibrillation is controversial, because of possibility of poor skin contact, arcing and risk of fire . Large metal environment may also predispose attendants to shock"(see NP Student's link above). Several studies I've read also said that the chamber needs to be decompressed to 1 ATA prior to use of a defibrillator. "Moreover the latency of bubble formation and onset of decompression sickness symptoms is sufficient to allow a brief excursion to 1 ATA for defibrillation, with subsequent return to previous pressures", so in an emergency the safety stop isn't strictly necessary.

Some other things that might help:

1. Wherever possible, instead of operating the chamber in an enriched O2 environment, it should contain standard atmosphere and supplemental O2 administered to the patient by mask (I know this isn't applicable for some treatments such as for wound healing).

2. All drapes. clothing, etc. in the chamber should be of nonflammable material or appropriately treated to make them nonflammable. Any other materials present should be nonflammable or self-extinguishing.

3. The primary concern with rapid decompression is bubble formation due to accumulation of dissolved N2 in tissue compartments. While as mentioned above the formation & onset of DCS is slow enough that it isn't an immediate issue, it's possible that an alternative inert gas mixture could be used to rapidly reduce the chamber ppO2. Similar to what we use for technical diving (heliox or trimix), something like helium, with it's much smaller molecule size, diffuses through the tissues more rapidly and minimizes the associated DCS risks. That said, DCS isn't immediately life threatening, while a cardiac code is.....

It should also be noted that most petroleum and organic oil based products (oils, lotions, etc,) can spontaneously combust in an O2 enriched environment and therefore should never be used prior to entering or while in such an environment. Only water based products should be used.

Good luck researching this - I'm interested in what you find out.

[313RN, BSN, RN]

OK, seriously, you guys full on ROCK!

I'll be doing more research and reading, and I'm extremely grateful for all the feedback.

I have a feeling you all summed it up quite nicely, but if I find anything that looks like it might contribute to your answers I'll certainly post it.

Thank you VERY much.