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Pulse Oximeter

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
most of them can be linked live to a PC. even the really old ones usually have a serial port that can stream the data to a telnet session
Thx for your answer. What I tought was of a small one like this one Seb mentioned.

Do you have an example of one (which is not too expensive)?
Quick search on eBay and here is one for you with a current bid of US$9.99 and a buy now price of US$150. This one has an RS232 port and for under $40 at most computer shops you can buy a USB convertor.

[ame=http://cgi.ebay.com/NELLCOR-N-200-PULSE-OXIMETER_W0QQitemZ360046377181QQihZ023QQcategoryZ31465QQssPageNameZWDVWQQrdZ1QQcmdZViewItem]+ NELLCOR N-200 PULSE OXIMETER - eBay (item 360046377181 end time May-01-08 19:00:16 PDT)[/ame]

You can get small portable units but still must have a proper sensor(earlobe) finger tip as explained is close to useless

Hope that helps
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It seems like the fingertip oxies are not popular here.
I find them very useful for checking when OXY starts to fall and how fast it falls.
Seem to be fairly accurate down to 70% (depending price).

Vaso does not seem to be an issue for me.

It seems like the fingertip oxies are not popular here.
I find them very useful for checking when OXY starts to fall and how fast it falls.
Seem to be fairly accurate down to 70% (depending price).

Vaso does not seem to be an issue for me.
The problem is that when the value on a fingertip oximeter starts to fall, it does not indicate falling O2 saturation in your body. It only indicates vasoconstriction, and that tells absolutely nothing about your real O2 saturation. So yes, to some degree it is useful, because it shows you when the diving response really kicks in, but it is useless for diagnosing your O2 saturation.
Yes, if you read posts at the beginning of this thread (or a few other threads about oximeters here on DB), you can see that it indeed works little bit better. The ear is close to the brain, and although there is certain vasoconstriction in skin everywhere anyway, it is less important than at the extremities. Eric Fattah uses a transcutaneous oximeter on his chest, which works better too, although also there the values are quite a bit off due to the vasoconstriction (or vasodilatation) in skin.
Hi to all. I have extensive experience with using a fingertip pulse oximeter. I have found it to be very useful in figuring out the effectiveness of breathe up and relaxation techniques. If you use one you should expect the reading to stay steady for the first few minutes after you start your hold. The length of time that is depends on your lung capacity, effectiveness of your relaxation techniques, and which hold you are doing. For me the reading starts dropping at about 4:15 on my last hold and then drops 8-10% per minute after that, and all the way down to 73% at the end of a 7 minute hold, so it is tracking pretty well. All of these numbers vary widely from person to person, but you get the idea. It is not perfect but is just one more useful tool. They are very inexpensive and can be found at Amazon.com. Search under "Pulse Oximeter." Their only limitation that I am aware of is their range goes from 70%-99%. I know I can get my O2 saturation below 70%, so at that point the device may become unreliable.

One way you can tell if yours is still working during a hold is if it shows a pulse. Mine shows a wave form. If you cut blood off, the wave form goes flat. I tried it by squeezing my finger with it on. So even if you get periferal vasoconstriction, you will still get some pulse through your finger. If the wave form goes flat, then you know your reading is unreliable.
What kind of Oximeter with earlobe sensor do you recomend?

I guess it`s a question about how much money you spend.
I just use normal fingertip pulse oximeter and it gives me good results. I don't think you get much vasoconstriction on dry holds anyway. I have gotten good readings all the way down to 73% at 7 minutes. Much lower than that and it may be unreliable because they are not calibrated below 70% I think. It may also depend on the one you buy. You can see me using one if you go to YouTube YouTube - wjohnson100's Channel where I have two recent posts, one a 7:00 hold and another a heart rate reduction demonstration.
There is a study comparing several types of fingertip sensor oximeters with an ear-lobe, and a reflective forehead sensor. All the five oximeters were newer types, using signal processing technology less sensitive to noise. Unlike common cheap oximeters, they are relatively big and expensive devices.

The study shows little difference between the fingertip and earlobe sensors. The reflective forehead sensor showed significantly better results, but all of the devices were within FDA standards (which allow maximally 3% root mean square error).

The problem with the study is that it compared the oximeters under induced hypoxia - the subject breathes air with lower content of oxygen. It means diving reflex does not make any effect. During a breath-hold, the situation is quite different - due to the diving response and especially because of the vasoconstriction, blood is much less saturated in extremities than in the core, hence measuring there does not really tell you what your SaO2 is, but rather how the blood is saturated in extremities. Depending on the strength of the diving response, the blood may be quite desaturated in extremities while still quite high in the core.

It means using fingertip oximeter is still interesting because it can show you how well the diving response kicks in, but it tells you only little about the SaO2 in your core, which is much more important for knowing your limits. So from this point of view, using an earlobe sensor, or better yet forehead or chest reflective sensor is giving you a little better information.

Using concurrently both types of sensors may be even better, since it will give you the complete information - how your core is supplied with oxygen, and how well the vasoconstriction progresses.

And yes, there is diving response and vasoconstriction at dry breath-holds too, so it does not apply for wet apnea only. There are certainly differences both between individuals, and between wet and dry apnea, in the strength and speed of diving response. That's why using just the fingertip oximeter does not really tell you much about your SaO2 - because you do not know how much is to be attributed to hypoxemia, and how much to vasoconstriction.
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I think I have to respectfully disagree with you on the effectiveness of a fingertip pulse oximeter. I still get indication of strong pulse in the fingertip all the way through a 7 minute hold, and the O2 still tracks. There is still blood flowing. There is no magical separation between core blood and extremity blood as long as there is still blood flow. As far as there being significant vasocontriction on a dry hold, I have difficulty believing that is a significant effect on a dry hold. I would like to see evidence of that.
There is no magical separation between core blood and extremity blood as long as there is still blood flow.

Well, there isn't complete 'separation' but there is a difference in O2 saturation. The more slowly blood flows at the extremities, the more O2 will be taken out of it by the time it gets measured by the oximeter. So if it's flowing very slowly due to peripheral vasoconstriction, samples taken at the extremities would show much lower saturation than those taken at the core (big needles, anyone?)

I think the relationship between hypercapnia and peripheral vasoconstriction it's pretty well accepted by medical science, there would be any number of studies that refer to it. Probably a few on Trux's site?
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I guess the good news there is that the fintertip oximeter gives you a conservative worst case O2 saturation. If that is the case though, there is no place you could get a good O2 saturation that you could reasonably measure with an oximeter, unless you figure some way of directly measuring carotid artery O2 sat. Even the earlobe oximeter would be suspect. For most of us, the only practical oximeter is the figertip one, since it it relatively inexpensive and gives results that can be compared. I think that is the oximeter's main benefit anyway, and I can see quantifiable differences in readings depending on how I do my breathe up. Recently I made a change in breathe up and got an immediate difference at the 6:00 point, consistently about 5% better. For me that is an extra 30-45 seconds on a 7:00 hold. now I am getting better saturations at 6:30 than I used to get at 6:00. That is what I need to know anyway. I suppose one way to test all of this would be to wear both a fingertip and earlobe sensor and see what the difference is on a long hold. Has anyone tried that?
As for vasoconstriction during dry breath holds - it indeed happens and you will find the evidence in many studies of the diving response (DR). There are many factors playing a role in the DR, and the "water" sensors (actually temperature sensors), although important, are only one of them. Then there are pressure sensors, which are another water-related factor, but there are still many others which act both in water and out of it.

The "worst case SaO2" (peripheral SaO2) may be quite misleading, and may differ from the core SaO2 very significantly and individually not only at each person, but also under different conditions. The main problem is that the desaturation of the core may start at a completely different moment than the desaturation of the peripheral system, hence the fingertip sensor may seriously mislead you.

It is not true that fingertip oximeters are the only practical ones because of their price - earlobe sensors are as simple and as cheap as fingertip types. Only reflective forehead or chest sensors use to be more expensive, but actually without a real reason and slowly become affordable for amateurs too. And although it is true that none of them will give the right values anyway (due to vasoconstriction in the skin), still they will be closer to the reality than a fingertip sensor, which is simply too far from the core.
Recently I made a change in breathe up and got an immediate difference at the 6:00 point, consistently about 5% better. For me that is an extra 30-45 seconds on a 7:00 hold. now I am getting better saturations at 6:30 than I used to get at 6:00.
That's exactly where the fingertip oximeter can seriously mislead you. If you use breath-up that suppresses the DR (more hyperventilation) the SaO2 values will appear good to you (since there is little vasoconstriction), but in reality the core may be already in dangerous level of hypoxemia.

And oppositely when your breath-up helps triggering a strong DR, the peripheral SaO2 will drop early in your breath-hold, and if you believe the values, you will abort the breath-hold, thinking you are already seriously hypoxic, while the exact opposite is true.

Hence be quite vary of using technology without knowing exactly what it does. It may send you the wrong way.
If you gain 5% O2 saturation at 6:00 by changing breathups, I guess one question to ask is whether this is a good thing or not... I mean, by hyperventilating I could probably reduce hypercapnia, reduce peripheral vasoconstriction and increase the O2 readings at my fingertip - but having oxygenated fingertips wouldn't be helping me to stay conscious.

Oops, didn't see Trux's post before sending this one...
I got the improvement by significantly reducing my breathe up intensity. And the improvement has been consistent. Before the changes I had done 7 minute holds before, but always hypoxic and at or near my limit. Last week I was able to do a 7 minute hold under total control, a first for me.

The improvement is definite.

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Yes, if you've decreased the intensity of your breathup to get the improved reading I think you can be pretty confident it's real.
Yea, right now my breathe up is as follows:

5:00 initial relaxation period, normal tidal breathing
5 purge breaths
3:00 hold
3:00 rest, normal tidal breathing
5 purge breaths
3:30 hold
3:30 rest, normal tidal breathing
5 purge breaths
4:15 hold
10:00 breathing in 2 sec, hold 4 sec, out 2 sec
5 purge breaths
5:30 hold
10:00 breathing in 2 sec, hold 4 sec, out 2 sec
5 purge breaths, no deep exhale, no packs
Final hold, today an easy 6:00

Before last week I was doing 2 minutes of rapid shallow breathing before the last two holds. I think that was causing me to start the hold in oxygen debt due to the increased respiratory activity, and causing O2 to stay bound to hemoglobin at the end of my holds due to the Bohr effect. I think that reducing breathe up intensity gave me extra O2 at the beginning and end of holds. That's my theory anyway. I will further reduce my breathe up intensity as my training progresses, I think. You would think that my holds would get more uncomfortable by doing that, but that is not the case so far. As far as the 7:00 hold goes, it was a major point in my progress because I was finally able to pass 6:45 in a strong enough position to go to 7:00 under control. I have no way of knowing yet, but I think that using current methods, my max will be somewhere in the 7:15 - 7:30 range. If I could just learn to be comfortable packing, I could push that out even further. It would be great to be able to do all of this in the water too.
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