PM's and Hybrid cars


I've been looking at new cars and I have a question regarding hybrid vehicles: Is it safe for those with pacemakers to drive hybrid cars, such as the Toyota Prius.

I ask this because someone told me today that these cars may interfere with the electronics in pacemakers---and I'm seriously considering a Prius V.

2 Comments

what DOES interfere

by JustKrs - 2012-09-15 10:09:54

I'm not an expert on pacemakers -- but I am an engineer and i have done some reading.
So far the way I understand it.. there are two basic things that can interfere with how your pacemaker works:

A) Electrical current being run in your body

A1. Reason: because the pacemaker sees the current and cant tell that from your hearts electrical workings and therefore cant tell if it should pace

A2. Some Example Causes:
electrocuting yourself,
electrocautery (a tool/procedure used during some surgerys to cauterize veins to stop bleeding),



B) VERY strong magnets/magnetic fields near you

B1. Reason: Magnetic fields CAN mess with electronics, its a risk not a guarantee. You would not put a huge magnet next to your computer hard drive because it could mess with some of the data... same thing, you don't want to put a huge magnet next to your pacemaker cause its electronics and it's not worth the risk.
ALSO, pacemaker companies program pacemakers to detect a very strong magnet being put on your chest to kick the pacemaker into a special mode. This is a safety feature so that a hospital/surgeon could quickly change the mode of your pacemaker.. but you don't want to trigger it randomly.

B2. Example Cause
MRI
HAM radios
Running engines/motors (you can drive, just dont put your pacemaker 6inches from the engine!. you can use a generator, just dont stand right over it and watch it)

You have the right idea

by ElectricFrank - 2012-09-16 12:09:06

A few comments that you will understand as an engineer ( I'm also one).

A. As far as current through your body, it depends on the path it takes. The modern pacemakers use co-axial leads for what they call bi-polar mode. In this case the sensing leads only read voltage between the 2 electrodes in the heart wall. So it takes a current path that includes the heart wall to be a problem. The sensing threshold is on the order of 1V . To keep things in perspective this is in the same range as the voltage used to cause the heart to contract. So a current that creates enough voltage to trigger the pacer would also cause even an un-paced healthy heart to contract. The only "gotcha" is that a lead failure will cause the pacer to revert to uni-polar mode with the pacer body being the other electrode and thwarts the whole advantage of the bi-polar leads.

B. The DC magnetic field issue is the effect of a reed switch in the pacemaker that switches the the pacer into a fixed rate (usually around 85bpm) with no sensing. That allows the use of O.R. equipment that could confuse sensing especially when they are doing surgery inside the body with all the high conductive fluids. Some pacemakers also use the magnet to switch the pacer into interrogation mode.

The effect of RF energy like HAM radios or the high frequency part of an MRI are entirely different problems. The frequencies are too high to be within the pacemakers (or hearts) operational range. The problem is RF rectification of high level signals in the input sensing amplifiers. It seems that the modern pacer uses RF filtering to suppress this condition.

Soooo, my personal experience. I have done the following without having any sense of a problem even though I am 100% dependent on the pacer.

I've stood within about a foot of the CB antenna on my jeep with the 5 watt transmitter keyed. I've also been very close to several 100watt and up HAM rigs when they are transmitting.

I inadvertently carried a woofer speaker from my Jeep into the house with it against by chest. It will grab a nail if it is close to the magnet. I routinely pick up my 1KW Honda Generator with it running and under load to move it when I'm camping.

So far I haven't found anything that affects it.

Don, on the site may jump in with his experiences as well. Between him and I we have just about tried everything.

frank

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