I understand that breathable air behaves differently underwater due to higher ambient pressure, and that for some reason it causes bubbles in your blood vessels if you ascend too quickly. But I couldn’t understand why that is.
Additionally, given the same supply of air tank, why is it the case that if you are living in a underwater habitat, then you can dive for longer hours as opposed to someone who came down from the surface?
In: Biology
Your blood and tissues absorb nitrogen at any altitude where there’s air pressure. As you descend in the water, pressure increases. Correspondingly, your blood and tissues are able to and do absorb more nitrogen as the pressure increases. It takes time for the nitrogen to accumulate (nitrogen saturation) in your system. As you ascend, your blood loses its ability to hold the nitrogen. It can come out of solution much the same way that a soda can releases its CO2 when it’s opened and the pressure is released. If you ascend slowly, the Nitrogen is gassed off and removed through respiration. If you ascend too quickly, the nitrogen bubble can form too quickly and end up in the tissues or bloodstream. This can cause a stroke, heart attack, or bends.
There’s not a problem going down because there’s little harm while the body accumulates the nitrogen. The problem is when you ascend. If you dive down from the surface, you need to ascend (come back up) slowly on return to the surface. If you plan to stay at depth under pressure (“In a habitat for instance), then there’s not a limit to your dive time because you’re not returning to the surface. When you do finally return to sea level, you’d need to ascend slowly to safely off-gas the nitrogen.
There is a condition known as Nitrogen Narcosis. Some people experience symptoms akin to those caused by Nitros Oxide at depth. This can be a very dangerous condition in that you’re underwater in an altered mental state.
Below 100 feet, there’s a risk of oxygen toxicity due to increased oxygen saturation. Deep divers use a special mixture of air to avoid this (nitrox)
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