Faulty PADI Question

[voidware]

I don't know whether to put this here or dive medicine, so please forgive me.

I recently took the PADI rescue diver course. On the final exam, I missed two questions. one was about the color of blood at depth, which didn't seem like it had any importance. The other was worded something like this:

Pain in the joints can be a symptom of arterial gas embolism. True-or-False

It was like three weeks ago, so I don't remember the exact phrasing, but the symptoms were similar to DCS. I put true. I am under the impression that AGE can have the exact same symptoms as DCS because they both can lead to bubbles in the tissues. When I discussed it with the instructor, he said that it was a subtle distinction that wasn't really important. Besides, the diver shouldn't diagnose. Just assess the need for treatment.

But can AGE cause pain in the joints and other DCS symptoms?

brandon

 

[ScubaJorgen]

Mmmmm....That's what they usually say, DCS sickness and AGE often lead to the same symptoms.

AGE symtoms are acute during ascent. Lungs (alveoli) are ruptured and air enters the bloodstream, immediately leading to embolism.

DCS symptoms occur minutes, hours or even days after the dive. Bubbles grow slowly, clog together and eventually start blocking arteries and veins.

During DCS micro bubbles can form anywhere in the body. Bones (joints) are the slower tissue compartments, probably less perfused with blood. Apparently they are succeptible to DCS, leading to itching and pain.

During AGE bubbles enter the body via the lungs and main arteries. I can think of that these bubbles are relatively large and never will reach the small veins (for the same reason the bubbles occuring in the tissue during DCS are not transported to the lungs). The AGE bubbles block larger arteries. If this occurs in the brain, severe symptoms occur, comparable to severe DCS symptoms (convulsion, etc). I would think AGE won't lead to minor symptoms like itching/pain in the joints.

However, I am not sure about the above. Perhaps one of the :doc:'s can give more info.

 

[The Iceni]

Hi Brandon,

You say

"I am under the impression that AGE can have the exact same symptoms as DCS because they both can lead to bubbles in the tissues. . . .Just assess the need for treatment. "

I can well understand your confusion and I am not really sure of the relevance of this exam question.

In a nutshell, an arterial gas embolism is simply any bubble of gas in an artery which may cause an obstruction to blood flow when it reaches the smaller blood vessels (the capilliaries) in the periphery. This occurs when the bubble diameter is larger than the vessel's (capillary) diameter. In addition, of course the bubble will grow in size if the external pressure is reduced.

There are subtle differences in the clinical features of DCI and mild AGE that to my mind really do not matter in the first-aid situation.

To my simple mind there exist two sources of DCI;

(NOT TO BE CONFUSED WITH TYPE 1 AND TYPE 2 DCI)

1) Authognous bubbles - those that grow in the supersaturated tissues themselves.

2) Emboli - those that arive from the arterial tree. (It is now thought by many that these exist even if the diver does not have a significant R-L shunt)

Each causes physical problems;

The primary injury in the first case is tissue compression. In the second it is an obstruction to blood flow leading to ischaemia (and tissue death).

Clearly external compression of the vascular supply to any organ will eventually lead to ischaemia . . and a growing gas embolus in a capilliary will itself cause tissue compression.

OK, A massive CAGE is obviously not simple DCI but does it really matter what actually originallly causes milder symptoms as the treatment is the same?

As for the colour of blood. Without artificial light blood simply looks black at depth in water, because of the loss of the red end of the natural light spectrum.

Again, I am not sure of the relevance of this question because the blood is still red and will be just as red when illuminated by white light.

Hope that helps.


ut:

 

[Walter]

Paul,

Excellent answer on DCS/AGE.

On the color of blood, you dropped the ball. Blood (at recreational depths) is green.

 

[Dr Deco]

Dear Readers:

[1.] Regarding arterial gas embolism , the major problem from an arterial gas phase is the embolization of the brain or spinal cord (less common). This occurs from lung overpressure problems during the ascent or within a few minutes of ascent. Pain is not commonly noted. In addition to pulmonary barotraumas, gas bubbles can enter the arterial system from passage though a PFO or through pulmonary shunts. Fortunately, these are not common occurrences for recreational divers.

[2.] The color of blood is modified by the blueness of the water unless one has a dive light. Of tangential interest is the effect of pressure on blood from a cut. People often believe, incorrectly, that the seawater pressure will cause water to leak into a cut. Contrariwise, they believe that the pressure will squeeze the body and cause the blood to squirt out of a cut. I have also heard “I had a metal plate placed over a hole in my skull. If I dive, will the pressure push the plate through the hole and into my brain?” Nothing will happen as the pressures in the body equalize in accordance with Pascal’s principle. Problems only exist in air-filled spaces such as the lungs and sinuses. :mean:

Dr Deco
:doctor:

 

[The Iceni]

Hi Dr Deco,

I am sure you know that I am aware of the considerable differences bewteen pulmonary barotrauma and consequential massive AGE, which are very serious and immediately life-threatening and the milder symtoms that may be caused by multiple small emboli, to which I was referring.

Which leads me to ask if you have any ideas or evidence on whether bubbles might actually form in the arterial circulation?Certain British cardiologists consider this to be a strong possibility but I have seen no evidence one way or the other.

It has been to postulated to be the cause of multiple small cerebral infacts found at MRI scan in divers with no history of DCI.

As for green blood. Light at 30 M in the North Sea is pretty limited and a diver's torch is almost considered a must on most dives!

*I will take a sample of blood with me on my next dive and report back!

Paul

 

[voidware]

Thanks Guys! Very informative answers.

Paul, that's a good idea. I'll be on some NC wrecks at ~120 (sand) and bring some blood. Maybe then I'll get to see some sharks.

brandon

 

[Dr Deco]

Hello Paul:

Spontaneous formation of bubbles in arterial blood is a good question. At the lower pressures involved in diving, I do not think this occurs even with very rapid decompressions of ten feet a second. We looked at that in sheep a while ago and found no evidence. {MR Powell, MP Spencer, MT Smith. In situ arterial bubble formation and atraumatic air embolism. Undersea Biomed. Res. 9, (1), Suppl., 10 (1982).} Brubakk et al. did seem to find some evidence of true arterial bubble formation but were not sure that they were not simply arterialization of venous bubbles {Brubakk AO, Peterson R, et al.Gas bubbles in the circulation of divers after ascending excursions from 300 to 250 msw. J Appl Physiol 1986 Jan;60(1):45-51}.

There is considerable interest in arterial bubble formation from artificial heart valves and the literature on this is considerable. Some recent articles follow: {Lin HY, Bianccucci BA, et al. Observation and quantification of gas bubble formation on a mechanical heart valve. J Biomech Eng 2000 Aug;122(4):304-9 ; Baumgartner RW, Frick A, et al. Microembolic signal counts increase during hyperbaric exposure in patients with prosthetic heart valves. J Thorac Cardiovasc Surg 2001 Dec;122(6):1142-6}

I believe that the jury is still out on the prevalence in “silent” arterial bubbles in divers. It is true that non-invasive scanning has indicated the presence of focal areas in divers, but these also appear in the brains of non-divers but with a lower frequency of occurrence. Thus it is unclear if this is related to pressurized gas and decompression effects.

Dr Deco:doctor:

 

[ScubaJorgen]

DrDeco wrote:

People often believe, incorrectly, that the seawater pressure will cause water to leak into a cut. Contrariwise, they believe that the pressure will squeeze the body and cause the blood to squirt out of a cut. I have also heard “I had a metal plate placed over a hole in my skull. If I dive, will the pressure push the plate through the hole and into my brain?” Nothing will happen as the pressures in the body equalize in accordance with Pascal’s principle. Problems only exist in air-filled spaces such as the lungs and sinuses.


To the same category as intruding water in wounds and imploding plates in heads fall the exploding heads in space.
This phenomenon is shown in bad-taste s-f movies when pressure drops due to leakage in space suits. Perhaps these movie makers take themselves as reference and think all people suffer from air-filled heads.

Ok, ok, ff:

 

[Walter]

Paul,

I've seen both fish and human blood on dives many times and it's always green.