Fizzy drinks and diving:

(Q) " 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 in hydration due to the caffeine and sugars, it shouldn't be a factor? Any thoughts?" 
(A)  Yes, my thought is not every IDC candidate belongs there.

With the exception of a very small number of nitrogenated beers, mostly European, the bubbles in effervescent 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.

Moreover, 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 secondary to gastric or intestinal rupture. However, it would be an extraordinary situation where expanding beverage bubbles would breach the GI wall rather than be expelled from one or the other end of the alimentary tract either by normal transit, 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 transported to the lungs where it is exhaled. As for any dissolved N2 passing from the GI tract to venous circulation, it wouldn't be transported by red blood cells, but nonetheless would wend its way to the lungs and then be off-gassed in the same way as C02.

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 obesity, diabetes and tooth decay, but in anything remotely resembling sensible quantities make no meaningful contribution to dehydration.


Doc Vikingo

This is educational only and does not constitute or imply a doctor-patient relationship. It is not medical advice to you or any other individual and should not be construed as such.

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