Have you ever wondered if you can go for a wreck dive in the morning, then pack up your gear, get in your car and drive up the mountains to go snowboarding in the afternoon? There may not be many geographical locations where this is possible at all, however, for the sake of this question let’s take a deeper look at this scenario. Let’s explain why going to altitude after diving may be a problem because of what happens to divers during dives.
Going to altitude after diving may be a problem because…
The very short explanation is that we absorb ‘Nitrogen’ when we scuba dive. This means we need to slowly release it when we get back to sea level, the equivalent of 1 bar of pressure. If we go to altitude, the atmospheric pressure drops and we are at increased risk of decompression sickness due to the pressure change.
When we scuba dive, we breathe higher partial pressures of both Oxygen and Nitrogen. This physics principle in scuba diving is known as Boyle’s Law. Depending on the depth and a gas’s solubility, we absorb it over time until it would eventually reach equilibrium.
The longer and deeper we dive, the more gas our body soaks up. The more gas in our body, the longer it will take for that gas to leave our body. We need to ensure that we release this gas gradually. Rapid pressure release is what causes decompression sickness or the bends.
Scuba diving no-decompression limits are usually based on 1 bar of atmospheric pressure (sea level, therefore ocean diving). Going to altitude after diving decreases atmospheric pressure and we could potentially get decompression sickness.
There is a more rapid pressure drop at lower altitudes, exemplifying this problem. Altitude divers specifically learn how to deal with the decreased atmospheric pressure when conducting dives in lakes at altitude.
What about the other way around?
Ok, sure. What about a few runs on the piste in the morning and a deep dive in the afternoon? While this solution may sound like a winner, there are still issues with this. In order to dive conservatively, we should be acclimatised to the atmospheric pressure at the surface of the body of water that we intend to dive in.
This is why altitude divers learn to wait a minimum of 6 hours upon reaching their destined dive location in the mountains, before going on the dive.
Marcel Korkus currently holds the Guinness World Record for the highest altitude scuba dive in the world.
So there you have it. Going to altitude after diving may be a problem because you will most likely still have residual nitrogen in your system and are therefore at increased risk of decompression sickness.