EBME Forums Forums Maintenance Technical Assistance 12v Mains Invertors-Ambulance Transfers

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 !

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

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.
Bob..

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.
Robert

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.

Have a look at the inverters in the CPC catalogue. They are robust and cheap.
www.cpc.co.uk
Robert

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 ?

This what we do.
Some answers for you....
1)Yes
2)Yes
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.