SUUNTO DX - Manual (Page 123)

10.4. Isobaric counterdiffusion (ICD)
ICD is the term used to describe the physiologic effect when the diffusion of different
gases occurs in opposite directions while under a constant ambient pressure. Partic-
ularly in diving, the gases are nitrogen and helium. ICD can produce the formation of
bubbles in tissues where the sum of helium and nitrogen pressures exceeds ambient
pressure. This situation may occur with trimix divers when they change to a deco gas
containing markedly less helium and more nitrogen than the previous mix. To avoid
ICD, it is advisable to carefully plan the gas changes so that the nitrogen percentage
does not drastically increase with each change.
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