Not all IDC students are created equal.
During my girlfriend’s IDC, a candidate talked about the dangers of drinking fizzy drink (like coca cola) and then diving. He was specifically saying that the bubbles in the drink would increase the chances of a DCS hit.
For me, the bubbles are in the stomach which is enclosed and away from the blood stream so apart from the possible changes to metabolism due to the caffeine and sugars, it shouldn’t be a factor?
Yes, I think one of the IDC candidates in your g/f’s class still has some important concepts to master.
For openers, with the exception of a very small number of nitrogenated beers, mostly European, the bubbles in carbonated drinks, including all sodas, are composed of carbon dioxide (CO2), not nitrogen (N2). And of course it is the latter that’s the gaseous culprit in DCS in recreational divers.
And you are right –- gas bubbles cannot enter the circulatory system from the GI system under anything resembling normal circumstances. It is theoretically possible that bubbles could enter blood circulation as a result of gastric or intestinal barotrauma, but it would be an extraordinary situation where expanding bubbles would tear the GI wall rather than be expelled from one or the other ends of the alimentary tract (i.e., flatulence or belching).
Small amounts of gas from swallowed CO2 bubbles might pass into venous circulation in a dissolved state. However, if this occurred the gas would be rapidly dispersed in the blood coursing to the heart and off-gassed without issue. C02 readily binds to the hemoglobin in venous red blood cells and is then transported to the lungs where it is exhaled.
You also mention the caffeine common to carbonated cola drinks. While that chemical does mildly increase the excretion of urine, this is only in amounts much greater than contained in a can or bottle of normally caffeinated soda. Given sensible consumption, caffeine’s contribution to dehydration, and therefore possibly to DCS, is negligible.
As for the sugars in sweetened soft drinks, these may promote obseity, diabetes and tooth decay, but in anything remotely resembling sensible quantities make no meaningful contribution to dehydration.