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The function of decompression models has changed with the availability of Doppler ultrasonic bubble detectors, and is no longer merely to limit symptomatic occurrence of decompression sickness, but also to limit asymptomatic post-dive venous gas bubbles.<ref name="Papadopoulou 2013" /> A number of empirical modifications to dissolved phase models have been made since the identification of venous bubbles by Doppler measurement in asymptomatic divers soon after surfacing.<ref name="Huggins 1981"/>
===Efficiency and safety===
Two criteria that have been used in comparing decompression schedules are efficiency and safety, where decompression efficiency is defined as the ability of a schedule to provide acceptable safety from decompression sickness in the shortest time spent decompressing, and decompression safety, or converely, risk, is measured by the probability of decompression sickness incurred by following a given schedule for a given dive profile. Since it is impracticable to eliminate all risk using current knowledge of the effects of several variables, risk is derived by statistical analysis of the outcomes of exposure and decompression profiles, and an acceptable risk is stipulated, which may vary depending on the circumstances of the application.<ref name="Edel 1980" />
=== Tissue compartments ===
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=== Decompression obligation ===
A decompression obligation is the presence in the tissues of sufficient dissolved gas that the risk of symptomatic decompression sickness is unacceptable if a direct ascent to surface pressure is made at the prescribed ascent rate for the decompression model in use. A diver with a decompression ceiling can be said to have a decompression obligation, meaning that time must be spent outgassing during the ascent additional to the time spent ascending at the appropriate ascent rate. This time is nominally and most efficiently spent at decompression stops, though outgassing will occur at any depth where the arterial blood and lung gas have a lower partial pressure of the inert gas than the limiting tissue. When a decompression obligation exists, there will be a theoretical safe minimum depth known as the [[decompression ceiling]]. {{visible anchor|Obligatory decompression stops}} will be indicated at a depth at or below the current ceiling.<ref name="Doolette et al 2015" />
=== Time to surface ===
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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
==== Altitude exposure, altitude diving and flying after diving ====
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* Early decompression stress biomarkers
* The effects of normobaric oxygen on blood and in DCI first aid
{{expand section|<ref name="Fogarty 2025" /> |date=May 2025}}
===Practical effectiveness of models===
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<ref name="Eckenhoff 1986" >{{cite journal |title=Direct ascent from shallow air saturation exposures |journal=Undersea Biomedical Research |volume=13 |issue=3 |pages=305–16 |last1=Eckenhoff |first1=R.G. |last2=Osborne |first2=S.F. |last3=Parker |first3=J.W. |last4=Bondi |first4=K.R. |year=1986 |publisher=Undersea and Hyperbaric Medical Society, Inc. |pmid= 3535200 }}</ref>
<ref name="Edel 1980" >{{cite report |url=https://diving-rov-specialists.com/index_htm_files/scient-b_73-analysis-deco-tables-calculated-by-non-u_s.pdf |title=Analysis of Decompression Tables Calculated by non-U.S. Navy Methods |via=diving-rov-specialists.com |first=Peter O. |last=Edel |date= 31 March 1980 |publisher=Sea-Space Research Company Inc. |___location=Harvey, Louisiana }}</ref>
<ref name="EOW" >{{cite journal |title=The Extended Oxygen Window Concept for Programming Saturation Decompressions Using Air and Nitrox |last1=Kot |first1=Jacek |first2=Zdzislaw |last2=Sicko |first3=Tadeusz |last3=Doboszynski |year=2015 |journal=PLOS ONE |doi=10.1371/journal.pone.0130835 |pages=1–20 |pmid=26111113 |pmc=4482426 |volume=10 |issue = 6 |bibcode=2015PLoSO..1030835K |doi-access=free }}</ref>
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<ref name="LeMessurier and Hills" >{{cite journal |last1=LeMessurier |first1=H. |last2=Hills |first2=B.A. |year=1965 |title=Decompression Sickness. A thermodynamic approach arising from a study on Torres Strait diving techniques |journal=Hvalradets Skrifter |volume=48 |pages=54–84 }}</ref>
<ref name=logodiving >{{cite web |url=
<ref name="Maiken" >{{cite web |url=http://www.decompression.org/maiken/Bubble_Decompression_Strategies.htm |title=Part I: background and theory. Bubble physics |last=Maiken |first=Eric |year=1995 |work=Bubble Decompression Strategies |access-date=11 March 2016 |archive-date=12 April 2016 |archive-url=https://web.archive.org/web/20160412210256/http://www.decompression.org/maiken/Bubble_Decompression_Strategies.htm |url-status=live }}</ref>
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