Can you get decompression sickness or the bends from breathing nitrogen?

Answer 1

From Scuba diving? ... yes since that is what causes decompression sickness. But if your question is whether you can get DCI from just changing your gas at the surface from air (21% oxygen and 79% nitrogen) to a nitrogen enriched air (i.e. 15% oxygen and 85% nitrogen) without diving or ascending to altitude? ... then the answer would be no. The nitrogen increase is not enough to result in decompression sickness ... but you would would start feeling hypoxic from the lack of oxygen the more you lower the oxygen concentration.

Answer 2

Decompression sickness, or 'the bends', comes from the fact that a gas is compressible. As you dive further and further the water pressure on your lungs increases. The pressure regulator on scuba gear very slowly ups the pressure as you increase your depth, keeping your lungs from collapsing. In the process the nitrogen gas in your lungs starts to permeate your body (very slowly and it does no damage.) If you change your depth from say 200m to 2 m in 60 seconds, but it took you 15 minutes to get down to 200m, then the nitrogen gas that was under pressure suddenly has a lot less pressure holding it in and tries to expand in your arteries and veins, bubbling up almost like a boiling pot. NOT A GOOD THING! The way to stop this from happening is to go slowly on the way up, stopping every so often to allow the gas to re pressurize and come out of your tissues.

You may also want to see the answer in the question "What does decompression mean in diving?"