Hi Colin.
We have just completed an installation on a Spectra Plus EPIOC with a Nellcor Puritan Bennett LP10 ventilator.
We were not happy about relying on the wheelchair batteries alone and so provided a 30Ah external battery set to go on the chair as the main battery set.
In addition we provided a 24v to 12v DC-DC converter connected to the wheelchair batteries which we can switch over to should the main battery set go flat or fail.
We also provided a charger for the main battery set as we discovered that the ventilator was not capable of recharging the main external batteries in a reasonable time if they were completely flat.
As you suggest we would insist on the manufacturers internal battery being in place.
I would like to avoid the generation of mains voltages on the wheelchair if I could. I would imagine there must be other solutions that don't involve the generation of mains voltages. The regulatory and testing requirements increase dramatically when mains is involved. The most recent issue of the standard indicates that they should also be of a medical grade with respect to insulation resistance, leakage, emissions and immunity etc.
The EMC emissions from the inverters should be considered for ventilators without metallic enclosures and shielding etc, as should the electrical noise conductivly transferred into and out of the wheelchair control system!
I suggest anyone contemplating this sort of thing should have copies of all the relevant standards to hand.
Get in touch if you would like to discuss any of this further.
Best regards,
Geoff
G.J. Harbach I.Eng MIED IIPEM
Clinical Technologist
Special Controls Service Manager
Posture and Mobility Services
West Midlands Rehabilitation Centre
91 Oak Tree Lane, Selly Oak
South Birmingham Primary Care NHS Trust
West Midlands.
Tel 0121 627 1627 Ext. 53238
-----Original Message-----
From: p=NHS NATIONAL INT;a=NHS;c=GB;dda:RFC-822=ASSISTECH(a)JISCMAIL.AC.UK;
Sent: Friday, June 28, 2002 2:37 PM
To: p=NHS NATIONAL INT;a=NHS;c=GB;dda:RFC-822=ASSISTECH(a)JISCMAIL.AC.UK;
Subject: Powering Ventiltors from Powered Wheelchair Batteries
Dear All
I'm writing to ask if any of you have ever been asked to make the necessary electrical connections to enable a ventilator to be powered from a wheelchair's +24V batteries. Here in Lothian, we have been asked to do this work for three patients over the last year. All of these patients use Breas Medical ventilators that have a +24V connection to enable the connection of an external battery pack. The result of the work is that the ventilator can be mounted on the rear of the powered wheelchair, on a specially manufactured tray, without the need for an external battery pack to be fitted to the wheelchair.
Powering the ventilator from the wheelchair batteries reduces the amount of hardware that has to be fitted to the powered wheelchair and it enables the external battery pack to be kept as a reserve supply for emergencies.
Recently the department in Lothian that provide the ventilators to patients has informed me that they don't know of any other centres that are providing these electrical connections and indeed they know that some refuse to do it. This surprises me because it seems logical to carry out this work. Initially I contacted Braes and I was informed that there would be no particular problem in making this connection. My risk analysis indicated that we could only proceed with this work if the ventilator had an internal battery supply that it would switch to automatically in the event of a failure in the wheelchair electrical supply. The internal battery pack provides approx. 1 hour of ventilation which is more than enough time to connect either the external battery or a mains supply.
My questions are, have any of you been asked to do this type of work and if so have you agreed or refused and what are the reasons behind your decision?
On a related issue, we have also powered communication aids from the powered wheelchair batteries. I have concerns about generating mains type voltages on wheelchairs. I've therefore avoided using handy mains voltage converters and I've included dc/dc regulators to convert from the wheelchairs +24V to the required dc voltage. Do any of you have views on the use of Handy Mains converters on powered wheelchairs?
Colin Geggie
Clinical Bioengineer
Rehabilitation Engineering Services
Eastern General Hospital
Seafield Road
Edinburgh
EH6 7LN
Tel. 0131 536 4695
Fax. 0131 536 4840
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