Decompression theory: Difference between revisions

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Gas switching during decompression on open circuit is done primarily to increase the partial pressure of oxygen to increase the [[oxygen window]] effect, while keeping below [[Oxygen toxicity|acute toxicity]] levels. It is well established both in theory and practice, that a higher oxygen partial pressure facilitates a more rapid and effective elimination of inert gas, both in the dissolved state and as bubbles.

In closed circuit rebreather diving the oxygen partial pressure throughout the dive is maintained at a relatively high but tolerable level to reduce the ongassing as well as to accelerate offgassing of the diluent gas. Changes from helium-based diluents to nitrogen during ascent are desirable for reducing the use of expensive helium, but have other implications. It is unlikely that changes to nitrogen based decompression gas will accelerate decompression in typical technical bounce dive profiles, but there is some evidence that decompressing on helium-oxygen mixtures is more likely to result in neurological DCS, while nitrogen based decompression is more likely to produce other symptomsymptoms if DCS occurs. However, switching from helium rich to nitrogen rich decompression gas is implicated in inner ear DCS, connected with counter-diffusion effects. This risk can be reduced by sufficient initial decompression, using high oxygen partial pressure and making the helium to nitrogen switch relatively shallow.<ref name="Doolette and Mitchell 2013" />

==== Altitude exposure, altitude diving and flying after diving ====