Safe Ascent: Theory, Tips and Tricks
When you venture underwater and experience increased pressure, such as during a scuba dive, the air you breathe contains inert gases like nitrogen, which gradually dissolve into your bloodstream. As you swim back to the surface, the nitrogen within your body expands, and this expansion usually poses no harm. The nitrogen can safely exit your body when you exhale. However, if you ascend too quickly, your body struggles to eliminate all the expanding nitrogen efficiently. Consequently, excess nitrogen begins to coalesce, forming tiny bubbles within your body's tissues and bloodstream. These bubbles possess elastic properties, akin to half-filled water balloons, and can change shape as they travel.
If your circulatory system fails to transport these bubbles to your lungs, they can impede the flow of blood and obstruct tiny capillaries, resulting in a slowdown in blood circulation and the accumulation of nitrogen in your tissues. Over time, these bubbles grow and accumulate in various tissues and joints, leading to a condition known as decompression sickness.
Once these bubbles reach your lungs, they face a different fate. Your body filters them out of your bloodstream, and they are subsequently expelled into the alveoli, the countless tiny sacs within your lungs. These sacs are reminiscent of miniature balloons. If you neglect to expel these bubbles by exhaling properly, they can lead to the rupture of these sacs, akin to how soap bubbles burst. The air within these sacs has to go somewhere, and that somewhere is your bloodstream. This can result in a dangerous condition known as an arterial-gas embolism, which can have severe consequences if these bubbles migrate to critical areas such as your heart or brain.
Decompression sickness and arterial-gas embolism are the most serious ramifications of a rapid ascent while scuba diving. However, it's important to note that other issues can also arise from such situations, making it crucial to understand the basics of bubble formation and the associated safety measures to mitigate these risks.
Know your equipment: Understanding the functions of your dive gear is fundamental to achieving proper control of your life support equipment. Regarding a proper ascent rate, this is particularly true of dive computers and buoyancy control devices (BC or BCDs). BCDs may have nuances in their control functions such as air path travel routes and locations of buttons. Dive computers will vary in ascent requirements and indicators. Ensuring familiarity with your equipment will allow for you to better understand how to operate safely underwater.
Vent Your BC: Release air from your BCD before ascending. This helps avoid a rapid ascent caused by growing air volume in your BCD.
Slow Your Ascent: A gradual ascent allows your body to release dissolved nitrogen safely. Slow down, even within the allowable ascent rate on your dive computer, for better gas adjustment.
Make Your Safety Stop: Taking a safety stop at 15 feet reduces the risk of bubble formation. Three minutes is adequate, but five minutes is even more effective in reducing decompression stress.
Take Care in the Last Few Feet: Bubbles grow fastest in the final 15 feet. Maintain a routine and check for clear ascent conditions, ensuring no remaining air in your BC, and ascending slowly. At 30 feet per minute, your ascent from 15 feet should be at least 30 seconds.
Be Conservative: Rest and hydrate after your dive, and extend your surface interval, especially following deep or repetitive dives. Relax and prepare for the next dive.
By following these tips, you can enjoy safer and more enjoyable diving experiences while minimizing the risks associated with rapid ascents.