Back in another life, I got a degree in Chemical/Biomedical Engineering. This degree is an outstanding pre-med degree if you want to be an anesthesiologist. As you could imagine, I might have had a few classes on physiology along the way. Follow me below the fold and I will let you in on why waterboarding is certainly torture.
Let's just focus on the physical aspects and forget for a second the mental aspects of being suffocated because my book knowledge lies with the medical aspects.
The human body has a strange set of sensors in it that in a lot of respects seem cobbled together. To me it is one just one more reason that evolution seems like the likely scenario.
One surprising example is the manner in which our body decides it needs to breathe faster. It seems intuitive that the body would measure the concentration of oxygen in your blood in some manner and when it got low, it would send a signal to the brain indicating that you are not breathing fast enough. This is not how it happens. For whatever reason, the body measures the blood concentration of carbon dioxide. This Rube Goldberg set-up seems to work fine as A) we are having this discussion, and B) every molecule of oxygen that your body uses forms one molecule of carbon dioxide, thus there is a nice one to one relationship between the two. Obviously if your blood carbon dioxide concentration is coming up, your oxygen concentration is going down, and you need to breathe faster.
This is obvious if you think about people that suffocate in low oxygen atmospheres or inert gases like nitrogen. They just keep breathing out the carbon dioxide, but don't take in enough oxygen. The carbon dioxide sensor never lets you know that you aren't getting enough oxygen and you pass out nice and peacefully. As you need less oxygen when passed out, you might survive for a long time like this if there is some oxygen in the atmosphere. If not, you die rather quickly and blissfully.
So what does this have to do with waterboarding? When the wet rag is placed across your nose and mouth, if you exhale, the air passes out from under the rag rather easily. When you then go to inhale, the suction vacuums it onto your face and you don't get very much air. Accordingly, the volume of air in your lungs is decreasing rather rapidly. Without any gas in your lungs to exchange carbon dioxide into, the carbon dioxide concentration in your blood rises faster than if you had a lung-full of air. The carbon dioxide sensor goes bonkers telling you to breathe, but you can't get much. Panic sets in rapidly sending your adrenaline through the roof. This is handy when you need to lift a car off of your child, but of course also increases your metabolism which while being waterboarded just sends your blood carbon dioxide level higher.
You can do a quick experiment to prove this to yourself, if you STILL have any doubts. Take a nice lungfull of air and hold your breath. Not too bad and you can hold it for a while as your body exchanges carbon dioxide into your lungs keeping the blood concentration low for a while. Now blow out every last bit of air in your lungs and try holding your breath. You should notice quite a difference as your blood cannot exchange carbon dioxide into your lungs sending the carbon dioxide level up in your blood faster. Now imagine that someone else controls when and how often you exchange this carbon dioxide. Add in gagging from aspiration of small amounts of water along with water up your nose and there can simply be no doubt that this is torture. Anyone who says otherwise is willfully ignorant or lying.
Blanchy