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Topic: Is it safe to connect Arduino to human body? (Read 6821 times) previous topic - next topic

Paul__B

The high price tag is probably due more to the test & documentation than to the cost of the technology (components) itself.
You better believe it!

This necessarily applies to all medical tools, surgical instruments and equipments, and implants.

Mind you, I suspect there is also an aspect of "what the market will bear" once companies have dominance, as there is with supermarkets. :smiley-evil:

raschemmel

#16
Jul 17, 2015, 08:58 am Last Edit: Jul 17, 2015, 11:18 pm by raschemmel
The "whatever the market will bear" immediately comes into play when marketing any device for monitoring tha heart because the interest in doing so indicates that the cardiovascular system has been compromised by age, lack of exercise or something more serious.. I almost killed my best friend by accident when I was 14 years old.  He was a Sherlock Holmes fan and was bragging about being a master of disquise so I invited him to my house knowing he would be walking and I put on my my mother's hat , overcoat, galoshes and white frame sunglasses and shuffled down the sidewalk , hunched over with my head down as he aporoached and then grabbed him by the shoulders and yelled
. His brain had told him I was a harmless old lady so he never gave me a second look. It took him completely by surprise. He almost went into ventricular fibrilation because he had a heart murmer as a child and had never told me. I freaked out when he started grabbing his chest. What 14 year old could anticipate that ?
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Paul__B

Fortunately ventricular fibrillation and congenital heart murmurs are not related. :smiley-roll:

He was perfectly durable; someone (over-protective mum?) was using that as an excuse to molly-coddle. :smiley-lol:

raschemmel

#18
Jul 17, 2015, 03:26 pm Last Edit: Jul 17, 2015, 04:15 pm by raschemmel
I think what he said when he grabbed is chest and started hyperventilating was "You almost gave me a heart attack ! I have a congenital heart valve defect." (The artificial heart valve technology in 1963 was not very advanced) I guess my point is that for some people, not being able to monitor their heart activity is not an option so they are at the mercy of the market price.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Paul__B

I am sticking with my analysis of your friend's cameo.  Hyperventilation indeed.  What they did not have in 1963 was cardiac ultrasound (and even II would have been a big ask) so what doctors said would have had a significant BS component.

Now of course, the good example of effective isolation - in fact precisely what far_1 describes, is the current generation of Holter monitor powered by two AA batteries and using an SD card.  (Well, at least the one I have had on me does that.)

This one is completely self-sufficient:

raschemmel

#20
Jul 18, 2015, 03:21 pm Last Edit: Jul 18, 2015, 03:44 pm by raschemmel
At the Hospital  Bedside Patient Monitor manufacturer factory I worked at in 1984, they made portable units for  the ambulatory heart patients  so the nurses could monitor the patients to and from the cafeteria. I don't recall seeing those in the U.S.A.F. hospital I worked in as a Medical ( not electronics) tech/ orderly (1969- 1971, Tachikawa ,Japan). I worked in ICU .
In the factory, the techs who worked in the RF dept on the other side of the aisle worked on testing, tuning, and calibration of the portable RF cardiac monitors
The patient wore electrodes and an iPod sized transmitter on their chest hanging from a neck-strap
They had high-end Spectrum Analyzers in that dept.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Paul__B

The patient wore electrodes and an iPod sized transmitter on their chest hanging from a neck-strap
Tell me about it!

Spent a few days on a couple of occasions wearing one in the cardio-thoracic ward.

Now interesting that while the "Holter" monitors have become smaller, the wireless monitors are still larger.  Because to operate the wireless, they require more battery power.

raschemmel

I don't know anything about FCC regs but I think there is a special frequency band reserved for hospital (or emergency services) wireless cardiac monitors. I don't know if civilian companies are allowed to use those for products like the one you have. I worked in the uP department of the factory so I don't know any technical details about the RF department (like carrier frequency).
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

harddrive123

If your measuring off the human body like heatbeat or electrical signals, using a op-amps isn't dangerous, they are high impedance devices.

This means that it has near infinite resistance (in reality its likely 10-100M) which means it conducts nearly no current.

Don't ever try to inject current into the human body, that's where stuff starts to get dangerous. Thats why isolation is important, so nothing high power can accidentally hurt someone.
Come check out hdtechs.ca

raschemmel

We already did an experiment with each foot immersed in saltwater  and 33V dc applied to the two waterpans (+ to one - to the other).  The current measured was in the uA to 1 mA range.
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

Paul__B

Op-amps may be high impedance devices, but only when operating correctly.

And ECG "dots" are made especially to have excellent contact.

So in any case, you include the 1M resistors in series with each input wire.

(You presumably do have to except the reference or "RL" - Right Leg - wire.)

polymorph

Also, don't forget you are connecting the patient to circuit ground. Ground currents that are not an issue to unbroken skin can become a hazard. There is a reason an operating theater has antistatic measures taken.
Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

raschemmel

Quote
Also, don't forget you are connecting the patient to circuit ground. Ground currents that are not an issue to unbroken skin can become a hazard. There is a reason an operating theater has antistatic measures taken.
I wouldn't advise that. As already mentioned, any circuit connected directly to human body should have isolation because in the event of a power supply failure, the output voltage of the power supply may exceed the +/- 15V on the op amps.  The circuit power should be isolated from patient side by an isolation barrier of some type.

(that includes circuit ground)
Arduino UNOs, Pro-Minis, ATMega328, ATtiny85, LCDs, MCP4162, keypads,<br />DS18B20s,74c922,nRF24L01, RS232, SD card, RC fixed wing, quadcopter

polymorph

Steve Greenfield AE7HD
Drawing Schematics: tinyurl.com/23mo9pf - tinyurl.com/o97ysyx - https://tinyurl.com/Technote8
Multitasking: forum.arduino.cc/index.php?topic=223286.0
gammon.com.au/blink - gammon.com.au/serial - gammon.com.au/interrupts

Paul__B

There is a reason an operating theatre has antistatic measures taken.
Yes, but it has nothing to do with electrocution hazard. :smiley-lol:

(You said: "antistatic")

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