On 05-Nov-08 16:49, Orchid XP v8 wrote:
>>> It means "electrocardiogram".
>>>
>>> I just had one.
> 
>> Great, why?
> 
> I keep having random chest pains for no defined reason. Presumably my 
> doctor wants to check it's not due to a life-threatening heart condition.

makes sense.

> 
> I still find it astonishing that they can build an amplifying powerful 
> enough and sensitive enough to detect the absurdly small electrical 
> currents, diluted across vast distances in space, and yet *not* pick up 
> the sea of EM interference in the room... Pretty amazing stuff!

EM (if you mean computers, mobile phones etc) is not the problem 
generally, mains power supply is.

I tried to find an image of the first string galvanometer in use, this 
is not the one I was looking for, but it will do:
http://en.wikipedia.org/wiki/Image:Willem_Einthoven_ECG.jpg

Note that this is a lead between a leg and the left arm. The buckets 
contain salty water. Here comes the part that may or may not amaze you: 
Here the patient is sitting next the machine. In actual clinical use the 
first one was 2 kilometer down the road connected with a telephone wire 
to the buckets in the hospital. There were actual two lines, one for the 
machine and one for Einthoven to talk to the clinician. At our ECG 
course I show this picture to the students, tell them about the 
telephone and ask them why that was technically possible then, but 
absolutely impossible with the current state of technology. Sometimes 
they get it, after some confusion.

>>> I didn't actually get to see the trace myself, 
>>
>> Do you think you could judge it yourself?
> 
> No. I'm just curios. (Personally I wouldn't even know a T wave from a U 
> wave...)

The T is the slow part after the QRS, the fast part with the highest 
excursions. The U wave may be after that. It is not present in every 
lead and not in every person. Frankly, no one knows what generates it.

>> I have electrodes all around the upper body. I regularly shave the 
>> front and sometimes even the back of very hairy men.
> 
> TMI?
?Can't find a relevant meaning for that acronym
> 
>>> Still, it could have been worse - if I needed an EEG, I really would 
>>> have to shave. O_O
>>
>> No, they generally use very different electrodes.
> 
> Sure. But I'd imagine you still need to shave your head to get them 
> anywhere near your scalp.

No. small electrodes fitted with conduction glue like material IIRC
> 
> What gets me is the people who try to *sleep* wearing those things...

This is from the company that builds our amplifiers, they are also used 
for sleep research so this could give you an idea: 
http://www.biosemi.com/applications.htm

>>> And fortunately, no blood samples required! :-D (Why do they always 
>>> have to take blood samples from the most tender parts of your 
>>> anatomy? Why not your finger or something? I'm sure it's the same 
>>> blood...)
>>>
>> 1) they do the finger for diabetes testing and also for testing at the 
>> blood bank.
>> 2) In don't know where you think they take blood, and possibly don't 
>> want to know. In my experience it is mostly from the arms.
> 
> Yeah - the soft, tender part in your elbow. What, they couldn't find 
> anywhere more painful? :-S
> 
Ah, it seems we have found a biological abnormality here. FYI, in most 
people the density of nerve endings in the elbow is much less tjan in 
the fingertips.

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