Doppler Bubble Monitor -Do you own/use one?

[DaleC]

Oh, I think doppler is a very useful tool, just not for the average recreational diver.

Using it, with enough time, dives, and attention to detail, you could create you own personal dive tables tailored to your personal reaction to decompression (it would take a lot of work). However, ones reaction to decompression is not static; it changes based on age, fitness, hydration, rest/stress etc... so even those tables would be a generalization.

You could use doppler to assess your reaction using standard deco models/tables and push them if you are robust in that regard but, just because you didn't bubble yesterday, that doesn't mean you won't get bent today. In would appear DCS is somewhat of a crapshoot, like the effects of narcosis.

So doppler really would be most effective post dive to register the amount of bubbling you are currently presenting. As an assessment tool, not a predictive tool. The question is: what do you do with that data? Do you rush to the chamber for pre-emptive treatment, re-descend for in water recompression, or wait for physical symptoms to manifest, if they do at all. I would think most would wait for physical symptoms, which is the indicative trigger for people without doppler testing.

I don't know if that makes sense. To me, doppler is too fine a tool for most recreational applications and gives too many false positive responses as far as DCS potential is concerned. A case of TMI. For aggressive divers it could be used to attempt to fine tune a deco model but there are a lot of variables that effect bubbling that make that somewhat akin to guestimating.

 

[lowviz]

...//... So doppler really would be most effective post dive to register the amount of bubbling you are currently presenting. As an assessment tool, not a predictive tool.

Agreed.

The question is: what do you do with that data? Do you rush to the chamber for pre-emptive treatment, re-descend for in water recompression, or wait for physical symptoms to manifest, if they do at all.

The plan is to get familiar with my own level of bubbling from diving standard profiles that work for me. If I see a higher level of bubbling than is usual, I'm done for the day. Nothing more exciting than that.

For aggressive divers it could be used to attempt to fine tune a deco model but there are a lot of variables that effect bubbling that make that somewhat akin to guestimating.

And for conservative divers, who find TMI interesting, it is just a form of direct feedback of admittedly questionable value. However, it IS direct feedback.

 

[Hickdive]

Very nice. There is however a point (slightly of topic) around PFO's I would like to mention, as a large % of divers don't know/understand. The fact that a PFO is not present on the day of the test does not mean that this will stay as is!

a Simple cough can damage and open up a PFO, same for lifting heavy objects, cardio illness, age, muscle disorders to name a few. You PFO status is not given!!!!

Listen to you body and dive safe!

A PFO test will normally require the subject to valsalva forcefully or perform another action to purposely open it.

---------- Post added June 7th, 2014 at 06:30 PM ----------

I have seen lay people using doppler to inappropriately "diagnose" otherwise asymptomatic divers as having decompression illness.

Of course, once that ball starts rolling it would be a very brave chamber operator who would turn such a diver away without re-compression.

I think DaleC pretty much nails it above.

 

[ajduplessis]

I am not sure about your statement around "actions to purposely open" a PFO during the testing procedure. Valsalva is performed to increase the pressure to help determine if a PFO (or partial opening) exsist.

Once a open, only surgery can close it up.

 

[lowviz]

...I think DaleC pretty much nails it above.

I agree. But leave a little room for us 'outliers'...

 

[Hickdive]

I am not sure about your statement around "actions to purposely open" a PFO during the testing procedure. Valsalva is performed to increase the pressure to help determine if a PFO (or partial opening) exsist.

Once a open, only surgery can close it up.

Sorry, my bad wording.

The subject will be required to forcefully valsalva to shunt bubbles across an existing PFO.

 

[DaleC]

There's nothing wrong with curiosity, and a common sense diver might find it interesting, I just don't think it would alleviate DCS in the gen pop.

 

[kwinter]

I agree with Hickdive. Maybe it is only semantics, but your Foramen Ovale is either Patent or it is not. You either have a PFO or not. This is not something that changes on a daily basis. Whether you actually shunt through an AV malformation is a different issue. For some (like myself) it takes deep valsalva to shunt through my small PFO. For others, even a minor increase in pressure is enough to do it. It is definitely not something that "once open, only surgery can close it up." Some people are candidates for closure with something like Amplaster. Others might be too small or asymptomatic.

I use my doppler after big dives or after any dive where I feel a little "off." The correlation between doppler-detected bubbles and DCS is a matter of debate.

 

[WhiteSands]

I want one! Will the $99 one work well enough for my purposes?

There are time I get headaches after a dive. Would be nice to just test if I have bubbles.

How do I use one? (Layman terms please...)

 

[lowviz]

WhiteSands, you don't give us much to go on with your profile. Your posts tend to be all over the place too, but I'll entertain your questions just the same.

I want one!

Me too.

Will the $99 one work well enough for my purposes?

It will tell you something, but it is up to YOU to decide what that 'something' is.

There are time I get headaches after a dive. Would be nice to just test if I have bubbles.

Can't say. Therefore, it is interesting (to some people like me) to test this. No clue as to what you will do with the result...

How do I use one? (Layman terms please...)

Oh, boy.

OK, here goes:
This manufacturer’s short explanation gives a good background for an initial understanding of this subject. Techno Scientific Inc.

These monitors were developed because they provide an easy way to detect a pulse. The ‘big picture’ of how this works is: send a pure single-frequency tone into the tissues and analyze the return echo for any changes in frequency. Imagine the sound of a speeding car approaching you, passing by, and then receding. The true sound of the motor is unchanging, but you don’t hear it as constant and you assume speed. Extremely crude approximation, but good enough. Look up ‘doppler shift’ if you want more.

Bubbles easily reflect the ultrasonic probe’s search signal even better than the collection of stuff in the moving blood stream. So, moving bubbles are very easy to monitor. The reflected signal will be shifted in frequency that relates directly to the velocity of the bubbles. We don’t care about the velocity, we just want to “count” or grade the level of bubbling. Bubbles sound very different than all the other stuff in blood. Listen for high frequency clicks, pops, squeals, etc. Most interesting…

This brings up another physiological phenomenon. Back when I was in research support, a physiologist suggested that I convert a maddeningly complex time-varying waveform (as seen on a spectrum analyzer) into audio and listen to it even though the signal had nothing to do with sound. Most enlightening result. The human brain has an incredible ability to detect and real-time analyze audio signals. So the point is, that the doppler monitor’s signals just ‘make sense’ to the ear and are rather easy to score.

If you were to be proper and scientific about it, you would be measuring bubbles in a certain part of the heart. No need for that level of sophistication. Dr. Gozum elegantly demonstrated his monitor by placing the probe on the neck, a bit of saliva instead of gel, just like one was looking for a carotid pulse. You will hear a distinct heartbeat with the occasional click or high frequency noise that indicates a bubble. It becomes quite easy to tell the difference after just a few minutes of experience.

Will the $99 model work? Don’t know. I don’t see why it wouldn’t, but yet to be proven. I'll post after I've had a chance to play with mine…