Waterproof ECG/EEG

G'Day all,

I'm attempting to make a waterproof ECG/EEG system. It's intended to be used as an analysis tool reasearching some of the physiological effects that happen to freedivers as they descend (ie breathold divers). It has been shown before that heart rates can drop as low as 3 bpm (that's one beat every 20 seconds), but I'm not aware of any analysis that's been done using an EEG. I therefore have some questions for the more technically minded - the sensors that are connected to the patient, is it required that they be waterproof? To what extent? And will this diminish their recording capabilities/sensitivity?

Many thanks,


Brad

https://jap.physiology.org/cgi/content/full/83/4/1282#SEC2
A study with four free divers in a hyperbaric chamber.

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Data logger for elephant seals..
speed,temperature (internal and external),heart rate, depth

Have a google with these rubriks >
human pulse transmitter Polar Electro Port Washington NY

Thanks mate - some good info there. Does this mean that there won't be any signal interference from the salt water if I just use normal electrodes?

Some sort of water proof coating or barrier is going to be needed
around the contact points, remember skin is porus and eventually
water will be absorbed , saturating the skin and in turn short
circuiting the ecg.

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is a quick solution, quite how it would perform
at depths of around 50meters they dont say.
I dont think they do a skull cap either.

Plan B>

The EEG to monitor brain waves is going to require the diver
to wear a full head helmet or after shaving thier head and
applying the leads a liberal coating of liquid latex should do the trick.
This should also work for the ecg connections as well.

Thanks for the help!

One more quick one - I also wouldn't mind adding some oxygen saturation meter to it... anyone have any ideas on how to build this, or where to look to find out? I tried googling but no luck - at a guess, I'd say it has something to do with shining IR light through the skin, and then measuring the change in the received signal?

Cheers,


Brad

Pulse oximetry is a state-of-the-art noninvasive method for determining the percentage of hemoglobin (Hb) saturated with oxygen.

Hemoglobin that is carrying oxygen (oxy-hemoglobin) absorbs light in the IR region of the spectrum; hemoglobin that isn’t carrying oxygen (deoxy-hemoglobin) absorbs visible red light.

In pulse oximetry, a clip containing 2 LEDs and the light sensor is placed on the patient’s finger or earlobe. One LED emits red light (600–700 nm) and the other emits light in the near IR (800–940 nm) region. The clip is connected by a cable to a microprocessor unit. The LEDs are rapidly and sequentially pulsed, and the detector is synchronized to capture the light from each LED as it is transmitted through the tissue. Backgrounds such as fluid, tissue, and bone are factored out of the measurement by monitoring the steady-state absorption from bone, tissue, venous blood, and arterial blood. During an arterial pulse there is an increase in blood volume, and this time-varying component is used to calculate the absorption of oxy- and deoxy-hemoglobin.

Note: this method will also provide heart rate data without the need for waterproofing.

Ps: have you considered taking readings of the blood and body core temperatures

Mate thanks again for the help - you sound like you know a lot about this, are you a doctor? Do you think that it's feasible that an amateur could actually implement something like this themselves?

As for other measurements, I'm not sure what you mean by blood analysis. Do you mean take a sample after the dive? On an extreme breathold dive, the body shuts down (its a survival response known as the mamallian dive reflex) - a lot of blood is drained from the limbs, and its redirected basically between the heart, lungs and brain. Core temperature should increase, but its not uncommon for the limbs to be freezing. These are the sort of things I wanted to record.

OK then, I'll rephrase - how many of these things do you think could be practically implemented by someone with only a university level understanding of electronics, and basic physiology knowledge?

SaO2 analysis
ECG
EEG
Blood pressure
CO2 levels

And maybe anything else you can think of that might be relevant?

Man, my diver is going to look like the bionic man when I'm done with him... :twisted:

Thanks again

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Ah, cheers Max karma to you

:lol: No ,not a doctor , more of an aging space cadet.

It's not overly complicated from an electronics view but it would be a lot to undertake for a lone individual to construct in a short period.

Incidently a helmet to keep the sensors dry is definitely no go as keeping the face clear of the chilled water will supress the dive reflex. You might want to include some additional nerve sensors to monitor the facial nerves as well.

Did find some good links for non invasive blood pressure sensors
these are of particular interest as they do not require the use of a
pressure cuff. This first one even has a link to circuit diagram.

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Thanks again - I'm not really worried about short period, I just want to make sure it all works properly. I'll have a go at drawing up a few diagrams over the next few weeks and stick them up here, see what everyone thinks.

Cheers again