Quiz - 26 - Diving Knowledge Workbook - Diving Physiology

[Pedro Burrito]

From the Diving Physiology Section of the PADI Diving Knowledge Workbook Version 2.02 © PADI 2009:

Objective 2.9 - Explain why individuals with DCS are given pure oxygen as a first aid measure.

Question 2

Breathing pure oxygen aids the individual with DCS because it:

a. enables the body to metabolize nitrogen more quickly.

b. increases the pressure gradient between the nitrogen pressure in the tissues and the alveolar nitrogen pressure.

c. decreases the pressure gradient between the nitrogen pressure in the tissues and the alveolar nitrogen pressure.

d. helps reduce the size of the bubbles.​

I will post a daily question from my exams to help newer divers and to encourage more experienced divers to interact gracefully and helpfully with the newer divers.

Reminder - this is a post in the Basic Forum and it is a green zone. Please be nice and on topic.

Thank you for your patience while we try to give people something to discuss other than Covid-19 and/or Politics. I will post the answer covered by the spoiler tag later today.

 

[spoolin01]

Looks like some confusion in interpreting the b and c choices. Or is the reason not the apparently obvious one?

 

[tridacna]

Looks like some confusion in interpreting the b and c choices. Or is the reason not the apparently obvious one?

B increases - C decreases. Pick your poison.

 

[-JD-]

B increases - C decreases. Pick your poison.

Sign (direction) not just magnitude matters

 

[spoolin01]

B increases - C decreases. Pick your poison.

Is there a physiologic dilemma, or just a semantic one?

 

[spoolin01]

Sign (direction) not just magnitude matters

Is this like how a lot of people say, when they drop to the bottom, that they are decreasing their depth?

 

[tridacna]

Is there a physiologic dilemma, or just a semantic one?

Neither - just a grammatical distinction!

 

[TMHeimer]

I picked one. I know what is happening with regard to the pressure gradient (why breathing 02 helps, etc.), just not sure about the direction wording. I can't recall "b vs. c" when I took the test, but that was a decade ago.

 

[EFX]

I got the answer right away. For me the clue was knowing the difference between pressure and pressure gradient.

 

[Angelo Farina]

Actually the term "gradient" here is used slightly improperly, as the pressure gradient is the ratio between the pressure difference and the distance "d" of the two points where you did measure the pressure:
grad(p) = (p1-p2)/d
Well, for being pedantic, the gradient is obtained as the limit of the above ratio when d is reduced towards zero...
So the correct wording should have been "pressure difference", not "pressure gradient".
Perhaps this confused some people, also because the term "gradient" is not really of common use outside a physics classroom. "Difference" is much simpler, and maintains the correct meaning...