EBME Forums
Posted By: Chris-H 12v Mains Invertors-Ambulance Transfers - 15/11/04 12:16 PM
Afternoon ,

I have searched previous threads but not found anything concrete regarding existing policy on the use of voltage invertors with medical equipment.
Someone please enlighten me.
You know the type you can order from places like Maplin Electronics, and RS components among many others.

Are they suitable for use with Infusion devices or patient monitoring?

I know we have had problems in past whereby one was used to step up from a 12v supply to mains 220vac. Only for it to be stepped down again via an external SMPSU for a patient monitor that was causing the SMPSU to overheat etc. Therfore we advised against using these devices.

We have yet to come accross one that is classified and certified as suitable for use with medical grade equipment.

There is also the issue of how many items are being plugged into this "Handy Mains" invertor?

It is quite viable for them to become potentially overloaded.

What or who governs the usage of these device in your organisation?

Damm that can of worms !
Posted By: Bioman Re: 12v Mains Invertors-Ambulance Transfers - 15/11/04 12:54 PM
There was a BSI committee concerned with ambulances/medical equipment, I recall that Jim Le Fever at the MHRA was on this committee. He may be able to point you in the right direction.

Some years ago I did get contacted by a company who was developing an inverter which he hoped to CE mark, unfortunately I don't recall who this person was or whether this product was actually launched.

Good luck Chris
Posted By: Peter Re: 12v Mains Invertors-Ambulance Transfers - 15/11/04 3:23 PM
Some medical equipment will only work with true sine wave inverters. I know this applies to certain CPAP equipment and I believe applies to some infusion equipment. It was hoped that our local future ambulances will be fitted with 1KW true sine wave invertors.
The cheaper units tend to be chopped square wave which can cause problems.
As for a policy I have not seen anything to date, but the manufacturers I have spoken to have always been able to advise if their equipment will work with true sine wave or not.
We use a STATPOWER inverter which was supplied by Philips (M3080A £247+vat at last asking)as the ambulance adaptor for their M3/M4 patient monitors. We are currently considering buying another two for infusion devices. The device is CE marked (as an inverter), and I agree with Peter that it needs to be a true sine wave inverter.
Posted By: RoJo Re: 12v Mains Invertors-Ambulance Transfers - 15/11/04 4:49 PM
As the kit works on low voltage inside why are manufacturers not giving us a low voltage input socket? It would save a lot of problems.
I know some manufacturers do and this is a consideration when purchasing equipment.
Posted By: RICK Re: 12v Mains Invertors-Ambulance Transfers - 16/11/04 8:16 AM
We successfully use the RS 468-2937. We limit the input current with a 10A fuse so that it will not overload the Ambulance. The senior ODA oversees the use of them. The usual problem is that someone plugs in an incubator which blows the fuse. The system handles a few pumps/monitors without a ptoblem, except for avoiding the surge at switch on by starting one instument at a time. We have heard that the newer ambulances in our region have them fitted as standard. I know nothing about the operational limits of these.
Posted By: RoJo Re: 12v Mains Invertors-Ambulance Transfers - 16/11/04 8:43 AM
Have a look at the inverters in the CPC catalogue. They are robust and cheap.
Right then !
So we agree, you all use them. Right. Agree.
Well ....
1) Are they logged in your asset register appropiately as a medical device?
2) Does your EBME encompase them into your yearly PM's?
3)What or who governs what medical device the inverter is used with. i.e does the user instructions state they are suitable for use with medical devices?
4) This leads on to leakage currents and classification, Are these inverters considered Class two (As I suspect) or class one?
5) If there were an internal elecrical fault with the inverter that (worst case) resulted in an incident, who takes the fall?
Sorry to push this one out again, however we feel this is not the end of the saga !

What are your ambulances currently doing about this on going demand for Mains voltage during patient transfers ?
Posted By: Font Re: 12v Mains Invertors-Ambulance Transfers - 17/02/05 9:40 PM
This what we do.
Some answers for you....
3)Labelled "For use with *******"
4)I would consider them to be class 1 as although they are not mains powered, the case is not "isolated". The case of the inverter if I remember correctly should be grounded to the chassis of the transporting device.I have seen a document produced by Philips/Agilent/HP which describes this, will try and dig it out to confirm!
As for leakages, I cant see how we would measure them, would the tester connect to the inverter then the device in to the tester? There is no earth return so I dont think a leakage would be measured? Also I dont think the basic handy mains would take the extra load!

5)We have had a handy mains fail, but no incident.

Resmed do true sine inverters for the CPAP's.

I agree with you that this area can be a bit of a minefield, if only the suppliers would design a DC input for the equipment, "the cost, the cost" I hear them cry! The new patient monitors have a good battery life, with a spare or two fully charged, this would be enough for any transfer.

I know, the users are saying "but what if the battery runs out and the spare"

Hope this gives you some ideas to ponder.
I would tend to concur with Chris - H last comment.i.e.
Have you contacted your ambulance service/Trust to enquire with them, what are THEY doing about the issue?
My initial slant on this is that if they are providing the transport system (the Ambulance vehicle) then it is them that should provide the means for powering Hospital devices in their Ambulance, as and when the needs arise (patient transfers for example)
I am sure there are regulations governing what can be connected to the Ambulance vehicle electrics, regarding power drain/capacity etc etc.(don't ask me what these may be though ?) but overall this type of specialist vehicle should be fitted with any correct power supply for it's likely purpose.
Does that make sense ? It seems logical to me,
Transport incubators have always had a “home-grown” element to them. I have seen some real lash-ups in my time, and frankly, some of the current “manufactured” ones appear to be little better (in my humble opinion, of course). But why all this talk about leakages currents etc.? Where is the “earth” in an ambulance then? Just "bond" everything together.

Rojo is on the right track, if the system was properly designed for its intended purpose in the first place (and why aren't they? they certainly cost enough) it would all be at 12 or 24/28 V DC anyway.

May I suggest that when the next transport incubator is pensioned off, someone has a go at hacking into it and coming up with a prototype for a DC system. Then publishing the results for all to admire (remember the “Brompton”, “Nuffield”, “Radcliffe” et al ventilators, the “Liverpool” tester etc. etc. – who among you wants to be immortalized and forever linked with the state-of-the-art, versatile, transport incubator? Yet another challenge of sorts, then). Hint – take a look at the venerable Vickers Model 77 (much beloved by Tony Dowman) and start from there!

Note in passing that RS claim that the 468-2937 gives a pure sine output. Has anyone actually checked this out, I wonder? Does it make any difference? smile
Posted By: Rajan Re: 12v Mains Invertors-Ambulance Transfers - 19/02/05 6:15 AM
The main problem with the transport Incubator is that it has to be switched on in the ward itself for some time to make it warm and suitable to keep the baby for transport.
If my memory is perfect, it has to be switched on for minimum 30 minutes to keep it stabilized.
If we design a incubator to operate on DC, then we must make arrangements for DC supply in the neonatal ward also.
Thatís why the invertor need arises
In the case of ventilators and monitors, they can be immediately put into use , once energized.

One more thing, if the out put of the invertor is not pure sine wave, it will create lot of harmonics, the power transformer of the incubator will gets heated up unduly and also gives out more (humming)noise..
Yes, Rajan. We will need a mains-powered DC supply for when our bold new design is parked up in SCBU. But we want to avoid all that transforming of voltages down, up, and then down again don't we? It all wastes power, after all. And let humming be consigned to the history books!

The need for the inverter arises, does it not, when we have to obtain an AC “mains” from a DC power source (eg, vehicle, or aircraft, batteries). What we are suggesting is to do away with the need for AC mains altogether (except when on the ward, as mentioned above).

But don't forget to consider DC operation of all the ancillary items also (monitor, pulse oximeter, suction, ventilator, syringe pump and what-have-you). We need to take a total-system approach here.

So get your thinking caps on, notebooks out, and go for it (I might even bung in my old Sunvic relay as the prize)!

Don't forget improvement of the thermal qualities of the incubator itself (polystyrene should do the trick). But one last hint – start by adding up the total wattage required. Before we get too excited, how many Amps are we talking about? And then look closely at the method of heating the incubator (as this is where the real energy gets eaten up).

No more clues now - over to you guys (and what else were you going to do this weekend, now that hunting with dogs is a thing of the past?). smile
Thanks for the Mention Geoff, they certainly saved a few lives did,nt they. smile

Hoping that you will be submitting your design, then, Tony! smile
Posted By: RoJo Re: 12v Mains Invertors-Ambulance Transfers - 21/02/05 10:54 AM
As I have commented on in other postings, Draeger do a heater pad that is a one shot device, generating warmth from a chemical reaction so using no electricity. A couple of the London hospitals that do child transfers and retrievals are using it as standard. Eeven though it is a disposable item it still works out cheaper than a costly incubator.
Yes Geoff a bit of common sense and forthought when chosing equipment for ambulances, why turn low voltage DC to mains and then back again inside the equipment. Purchase equipment that is suitable for the job.
Hi Robert, I know you,ve moved on, but just out of interest, were you involved at all at Great Ormond Street with the Baby Medivacs from The Royal Hospital in Muscat Oman ??. smile I know the Biomeds there used to re-crate our Model 77,s for that evening,s Gulf Air return flight to Seeb. The Doctor and Nurse that accompanied the child got a 36hr jolly in London, but as I,ve said in a previous post all the Biomed got to see was the Underbelly and then inside of a 747.!! Just a thought wink circa 1988-1996
Posted By: RoJo Re: 12v Mains Invertors-Ambulance Transfers - 21/02/05 1:07 PM
I was only there for a couple of years from 2003-2005 so I did not have that joy. Royal Brompton and Harefield from 1990 before that.
Full CV available on request. laugh
Thanks for the offer of a CV I,m sure the
" Buddies " would like one laugh A word of warning from across the Pond. Seems the latest Identity Thefts in the US are from CV,s or should I say Resume,s, being posted on Forums like this. mad Maybe we should be more careful re addresses and phone no.s wink
Posted By: Huw Re: 12v Mains Invertors-Ambulance Transfers - 21/02/05 2:12 PM
...and now back to the thread, please wink
Posted By: Rajan Re: 12v Mains Invertors-Ambulance Transfers - 22/02/05 2:16 AM
The heater pad may a thermo ware type(disposable one)
If any emergency procedure to be done , then the medical personnel accompany the child, the doctor has to face a hell of time.
Any how, can you give me the tech/specification details of the blanket wrapper so that I can pass it on to pediatrician friends
Posted By: RonS Re: 12v Mains Invertors-Ambulance Transfers - 22/02/05 10:16 AM
I was about to comment on Resmeds true sine-wave inverter for CPAP use, but Font has beaten me to it...

If memory serves, and it may well not, the inverter was made by an Aussie company called Powerbox, was CE marked (tho don't quote me if it ain't!), cost about a hundred quid plus VAT a couple of years back, and was capable of delivering 350W. Not a huge amount of "juice" I know, but I would guess Powerbox would make beefier ones.
Posted By: Font Re: 12v Mains Invertors-Ambulance Transfers - 23/02/05 9:48 PM
RE: Grounding inverter to Ambulance.
I have converted the application sheet for HP M3080A inverter for use with M3 monitor to PDF format, I would attach it to this post if I could for you all to look at. Quality is not up to much as it was originally a FAX. Have e-mailed it to Huw to place on website somwhere!
Posted By: Huw Re: 12v Mains Invertors-Ambulance Transfers - 23/02/05 10:38 PM
Nice one Font smile

Here's the link to the M3080A (81Kb)

If I can clean it up or get an original version - I'll add it to the downloads section.
Have you tried Merlin Equipment Limited. They specialise in mains inverters for vehicles. They supply the Ambulance service, Fire Brigade, Police etc.

They can supply the STATPOWER (now Xantrex) inverter, which was supplied by Philips (M3080A £247+vat) at a fraction of the cost. They also do a higher power (75 watt) version of the Philips device (also known I believe as the Notepower 50).

Their details are:-

Merlin Equipment Limited
Unit 4, Cabot Business Village
Cabot Lane
Dorset BH17 7BA
United Kingdom

Tel: +44 (0)1202 697979
Fax: +44 (0)1202 691919

Thanks for all of that information people, however the issues we are facing are to do with the regulations and Trust / Ambulance service proceedures and policies.

Is there a policy that says for instance" It's current Trust policy NOT to use mains inverters with medical devices"?
Or an Ambulance service policy that states "All mains operated devices are to used in conjuction with ambulance fitted equipmanet(inverters) ONLY" etc.

More to the point Do your ambulances have Mains Inverters fitted to them?

I feel this is only the tip of the iceberg. One that is slowly melting, sending those already in the cold, plunging into to depths of those icy waters !
If you want any help on power management on emergency vehicles, please contact us!
We have a range of inverters commonly used by the emergency services with a new 1500W sinewave inverter just been launched.
Have a look on www.antares.co.uk for further details.
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