Editing Decompression sickness (section)

=== Isobaric counterdiffusion ===
{{Further|Isobaric counterdiffusion}}

DCS can also be caused at a constant ambient pressure when switching between gas mixtures containing different proportions of inert gas. This is known as [[isobaric counterdiffusion]], and presents a problem for very deep dives.{{sfn|Hamilton & Thalmann|p=477}} For example, after using a very helium-rich [[trimix (breathing gas)|trimix]] at the deepest part of the dive, a diver will switch to mixtures containing progressively less helium and more oxygen and nitrogen during the ascent. Nitrogen diffuses into tissues 2.65 times slower than helium but is about 4.5 times more soluble. Switching between gas mixtures that have very different fractions of nitrogen and helium can result in "fast" tissues (those tissues that have a good blood supply) actually increasing their total inert gas loading. This is often found to provoke inner ear decompression sickness, as the ear seems particularly sensitive to this effect.{{r|burton2004}}