why must scuba divers ascend to the surface at a controlled rate after a deep sea dive?
At exceptionally deep dives additional nitrogen dissolves in the blood stream of the diver. A slow ascent allows the elemental N2 to escape from the blood stream and be exhaled through the lungs. This "cleansing" process doesn't take place immediately; therefore, the ascent must be slow to allow this exchange time to take place.
Scuba divers must ascend to the surface at a controlled rate after a deep-sea dive because of a phenomenon called decompression sickness, also known as "the bends." Allow me to explain how this happens:
When you dive underwater, the pressure increases as the depth increases. This pressure causes gases, mainly nitrogen, to dissolve into your body tissues and bloodstream. During your dive, your body becomes saturated with these dissolved gases.
Now, when you ascend too quickly, the pressure on your body decreases rapidly. This reduction in pressure causes the dissolved gases in your body to come out of the solution and form bubbles. If these bubbles are formed within the tissues or bloodstream, it can lead to decompression sickness.
Decompression sickness can cause a range of symptoms, including joint pain, dizziness, fatigue, and in some severe cases, paralysis or even death.
To avoid decompression sickness, scuba divers follow a specific ascent rate called the "no-decompression limit." This limit indicates how much time a diver can spend at a certain depth without needing to make decompression stops during the ascent. The no-decompression limit varies based on the depth and duration of the dive.
To ascend safely, a scuba diver should ascend at a controlled rate, typically not exceeding 9-18 meters (30-60 feet) per minute. This allows the body to gradually reduce the accumulated gases and release them harmlessly before reaching the surface. During the ascent, divers may need to make decompression stops at specific depths to off-gas further. These stops allow the excess gases to be eliminated slowly from the body.
Additionally, scuba divers should follow the "safety stop" practice, which suggests making an additional stop at around 3-5 meters (10-15 feet) for 3-5 minutes as an extra safety measure during the ascent.
By ascending at a controlled rate and following proper decompression procedures, scuba divers can minimize the risk of decompression sickness and ensure a safe return to the surface.