Quiz - 24 - Diving Knowledge Workbook - Diving Physiology

[The Chairman]

If I may drift Off Topic a bit...

I LOVE THESE QUIZES! Thank you, thank you, thank you.

Go back to your silent bubbles now!!!

 

[Angelo Farina]

Precisely. Ultrasound detects bubbles. Doppler detects flow.
Now, we have done spoiled it for everyone...

Not so simple. The device is made of an ultrasonic narrow band emitter and a broadband receiver.
The ultrasonic beam has a precise frequency. The flow makes the frequency to change slightly: the frequency shift, due to Doppler effect, is proportional to the velocity of fluid. Hence both ultrasonic and Doppler measure the velocity.
The presence of bubbles do not affect the velocity measurement, hence is not related to ultrasound, nor to Doppler.
Simply the bubbles produce low frequency noise, in the audible frequency range. Connecting headphones to the instrument you can actually hear the noise of the bubbles.
For a quantitative analysis you need to take into account the noise level and its spectrum. The larger the level, the larger the quantity of bubbles gurgling through the vase.
The higher the pitch, the smaller are the bubbles...

 

[Scraps]

Precisely. Ultrasound detects bubbles. Doppler detects flow.
Now, we have done spoiled it for everyone...

The teaching value outweighs the spoiling offense.
Thanks.

 

[TMHeimer]

The teaching value outweighs the spoiling offense.
Thanks.

Exactly. Gotta go--not sure my Doppler Ultrasound Flowmeter is working properly.
Actually, I do have to go for an ultrasound, postponed because of Covid.

 

[Pedro Burrito]

Spoiler: Answer

d. Doppler Ultrasound Flowmeter

This question was not multiple choice in the book, it was fill in the blank. I added the other three choices for fun.

A pre-cordial Doppler Ultrasound Flowmeter can enable scientists to "hear" the silent bubbles as they travel in the venous circulation to the lungs. This phenomena is used as a criterion in testing decompression models and some dive tables/computers.

 

[Couv]

O'Dive One - O'Dive

 

[Angelo Farina]

My understanding is that the amount of bubbles you can detect in large vases has a very weak correlation with the insurgence of DCS symptoms.
In most cases DCS is related to what happens in remote districts with poor vascularization, or in nervous synapses.
What happens in the blood only explains a fraction of the cases...

 

[Vitesse2l]

We had a dive doctor give a talk one club night and he played a recording of bubbles in a diver just surfaced. About twelve months ago but from memory it was an ordinary 30m dive (so 100' ish), no deco or exertion and SS carried out. I think he said the ultrasound thingy was placed somewhere around the collarbone.

Listening to it made me wonder what I was even thinking of going that deep and then hauling out onto a rib. At the time, anyway...