Haldane's decompression model: Difference between revisions

Revision as of 18:28, 13 August 2024

Latest revision as of 23:02, 17 July 2025

(5 intermediate revisions by 4 users not shown)

Line 14:

}}

'''Haldane's decompression model''' is a [[mathematical model]] for [[Decompression (diving)|decompression]] to sea level atmospheric pressure of divers breathing compressed air at ambient pressure that was proposed in 1908 by the Scottish physiologist, [[John Scott Haldane]] (2 May 1860 – 14/15 March 1936),<ref>[{{cite web |url=http://navxdivingu.blogspot.ae/2009/10/diving-history-john-scott-haldane.html "|website=The United States Navy Experimental Diving Unit |date=28 October 2009 |title=Diving History -- John Scott Haldane "]Father of Modern Decompression"....and a bunch of other stuff }}</ref> who was also famous for intrepid self-experimentation.

Haldane prepared the first recognized [[Decompression theory#John Scott Haldane|decompression table]] for the [[British Admiralty]] in 1908 based on extensive experiments on goats and other animals using a [[clinical endpoint]] of [[symptom]]atic [[decompression sickness]].<ref name="haldane" /><ref name=":0">{{Cite journal |last=von Lünen |first=Alexander |date=2006 |title=Goats and gases: "The Prevention of Compressed Air Illness" by Haldane et al--A commentary |url=https://pubmed.ncbi.nlm.nih.gov/17078317 |journal=Wilderness & Environmental Medicine |volume=17 |issue=3 |pages=195–196 |doi=10.1580/06-weme-lh-028 |issn=1080-6032 |pmid=17078317}}</ref> The model, commented as "a lasting contribution to the diving world", was published in the ''[[Journal of Hygiene]]''.

<ref name=":1">{{Cite book |last1=Lang |first1=Michael A. |url=https://semspub.epa.gov/work/10/100006143.pdf |title=Diving for Science 2009: Proceedings of the American Academy of Underwater Sciences 28th Symposium |last2=Brubakk |first2=Alf O. |date=2009 |publisher=American Academy of Underwater Sciences |editor-last=Pollock |editor-first=N.W. |pages=112–124 |language=en |chapter=The Haldane Effect |chapter-url=https://www.tecvault.t101.ro/Haldane%20effect.pdf}}</ref>

Haldane observed that goats, saturated to depths of {{convert|165|ft|m}} of sea water, did not develop [[decompression sickness]] (DCS) if subsequent [[Decompression (diving)|decompression]] was limited to half the ambient pressure. Haldane constructed schedules which limited the critical supersaturation ratio to "2", in five hypothetical body tissue compartments characterized by their halftime. Halftime is also termed [[Half-life]] when linked to [[Exponential decay|exponential processes]] such as [[radioactive decay]]. Haldane's five compartments (halftimes: 5, 10, 20, 40, 75 minutes) were used in decompression calculations and staged decompression procedures for fifty years.<ref>{{Cite journal |last=Wienke |first=B.R. |date=1989 |title=N2 transfer and critical pressures in tissue compartments |url=https://linkinghub.elsevier.com/retrieve/pii/0895717789904421 |journal=Mathematical and Computer Modelling |language=en |volume=12 |issue=1 |pages=1–15 |doi=10.1016/0895-7177(89)90442-1|url-access=subscription }}</ref>

Previous theories to Haldane worked on "uniform compression", as Paul Bert pointed in 1878 that very slow decompression could avoid the [[caisson disease]], then Hermann von Schrötter proposed in 1895 the safe "uniform decompression" rate to be of "one [[Atmosphere (unit)|atmosphere]] per 20 minutes". Haldane in 1907 worked on "''staged decompression''" – decompression using a specified relatively rapid ascent rate, interrupted by specified periods at constant depth – and proved it to be safer than "''uniform decompression''" at the rates then in use, and produced his decompression tables on that basis.

Line 39:

===Paul Bert===

[[Paul Bert]] (17 October 1833 – 11 November 1886) was a French physiologist who graduated at Paris as doctor of medicine in 1863, and doctor of science in 1866. He was appointed professor of physiology successively at Bordeaux (1866) and the Sorbonne (1869). Paul Bert was given the nickname of "Father of Aviation Medicine" after his work, ''La Pression barometrique'' (1878), a comprehensive investigation on the physiological effects of air-pressure, which pointed out that the symptoms of [[caisson disease]] could be avoided by means of very slow decompression. However, his work did not furnish data about safe decompression rates.<ref>[{{cite book |url=https://hagstromerlibrary.ki.se/books/1537 |title=La pression barométrique. Recherches de physiologie expérimentale |last=Bert |first=Paul |___location=Paris |publisher=G. ]Masson |date=878 |via=hagstromerlibrary.ki.se}}</ref><ref>{{cite journal | pmid = 360338 | volume=34 | issue=1 | title="La Pression barométrique": Paul Bert's hypoxia theory and its critics | journal=Respir Physiol | pages=1–28 | last1 = Kellogg | first1 = RH | doi=10.1016/0034-5687(78)90046-4| year=1978 }}</ref>

===Schrötter===

Line 71:

* [[File:From Haldane's Book - Figure-1 N2 Saturation.jpg|thumb|The rate of saturation of any part of the body with nitrogen]] The rate of solubility of nitrogen per unit mass of tissue, varies greatly in different parts of the body, hence, after a sudden rise in air pressure, varies correspondingly.

* If the pressure is rapidly diminished to normal after exposure to saturation in compressed air, the venous blood will give off the whole of its excess of dissolved nitrogen during its passage to the lungs. If gas bubbles are formed in consequence of too rapid decompression, they will increase in size by diffusion into them, and thus cause blocking of small vessels. In order to avoid the risk of bubbles being formed during decompression, the decompression should be slow, and the rate of blood circulation can be increased considerably by muscular exertion.

* [[File:Haldane's Desat of N2 with different parts of the body with half-sat in 5-10-20-40-75 minutes.jpg|thumb|Decompression needs to be ''staged decompression'']][[File:Haldane's Desat of N2 different body tissues.jpg|thumb|Desaturation during ''uniform decompression'']] When a diver goes down for a very short time, the time occupied in the descent and ascent is taken into account. During descent, the diver is being saturated with nitrogen, so he should descentdescend as rapidly as practical. During ascent on the other hand, Haldane showed that at the end of decompression there is a dangerous excess of saturation in all parts of the body except those which half-saturated in less than about seven or eight minutes. The goats used for stage decompression experiments were subjected to uniform decompression in same time and exposure, and within thirty-six decompression trials, one died, two were paralyzed, one had indefinite general symptoms of severe character, and eleven other cases of "bends" occurred beside two doubtful cases.

* Diving period:

:* For short diving periods of less than seven to eight minutes with no repetitive dive: Haldane's experiments on goats showed that sudden decompression in less than a minute after exposures up to four minutes at {{convert|75|psi|bar|abbr=on}}, equivalent to {{convert|42|m|ft}} of sea water, goats did not develop any symptoms, even when exposures were raised to six minutes in some cases. This coincides with reports at that time from the Mediterranean of skilled Greek divers, diving to {{convert|30|fathom|m}} who, should their gear become entangled on the bottom, will cut their air-pipe and line, and blow themselves up to the surface in less than a minute.<ref name="haldane" />

:* With dives exceeding a few minutes or brief repetitive dives: Hill and Greenwood compressed themselves to {{convert|91|psi|bar|abbr=on}}, equivalent to {{convert|53|m}} of sea water, a very high pressure and risky experiment, and had bends after decompression. [[File:From Haldane's Book - N2 Saturation for different body tissues.jpg|thumb|The saturation curves of Hill and Greenwook's experiment for parts of the body]]The saturation curves of their experiment for parts of the body were published in 1908.<ref>{{Cite journal |last1=Hill |first1=Leonard Erskine |last2=Greenwood |first2=Major |date=1908-02-04 |title=The influence of increased barometric pressure on man. No. 4.—The relation of age and body weight to decompression effects |url=https://royalsocietypublishing.org/doi/10.1098/rspb.1908.0003 |journal=Proceedings of the Royal Society of London. Series B, Containing Papers of a Biological Character |language=en |volume=80 |issue=536 |pages=12–24 |doi=10.1098/rspb.1908.0003 |issn=0950-1193 |jstor=80220|url-access=subscription }}</ref>

[[File:Haldane - Bends of fore-leg in a goat.jpg|thumb|220px|right|One of Haldane's bent goats. Note the bend in the left foreleg.<ref name=haldane>{{Cite journal |date=June 1908 |journal=The Journal of Hygiene |volume=8 |pages=342–443 |number=3 |pmid=20474365 |pmc=2167126 |last1=Boycott |first1=A. E. |title=The Prevention of Compressed-air Illness |last2=Damant |first2=G. C. |last3=Haldane |first3=J. S. |url=http://archive.rubicon-foundation.org/7489 |doi=10.1017/S0022172400003399 |access-date=12 May 2015 |archive-url=https://web.archive.org/web/20110324171946/http://archive.rubicon-foundation.org/7489 |archive-date=24 March 2011 |url-status=usurped }}</ref>]]

* Experiments continued on goats, and symptoms observed on goats were noted each time on appropriated schedule to record the presence of symptoms not the presence of bubbles:

Line 99:

==Further developments on Haldane's principles==

The 2:1 ratio proposed by Haldane was found to be too conservative for fast tissues (short dives) and not conservative enough for slow tissues (long dives). The ratio also seemed to vary with depth. The ascent rates used on older tables were {{convert|18|m/min}}, but newer tables now use {{convert|9|m/min}}.<ref>{{Cite journal |last1=Carturan |first1=D. |last2=Boussuges |first2=A. |last3=Vanuxem |first3=P. |last4=Bar-Hen |first4=A. |last5=Burnet |first5=H. |last6=Gardette |first6=B. |date=2002-10-01 |title=Ascent rate, age, maximal oxygen uptake, adiposity, and circulating venous bubbles after diving |url=https://www.physiology.org/doi/10.1152/japplphysiol.00723.1999 |journal=Journal of Applied Physiology |language=en |volume=93 |issue=4 |pages=1349–1356 |doi=10.1152/japplphysiol.00723.1999 |pmid=12235035 |issn=8750-7587|url-access=subscription }}</ref><ref>{{Cite journal |last1=Carturan |first1=D. |last2=Boussuges |first2=A. |last3=Molenat |first3=F. |last4=Burnet |first4=H. |last5=Fondarai |first5=J. |last6=Gardette |first6=B. |date=2000 |title=Ascent Rate and Circulating Venous Bubbles in Recreational Diving |url=http://www.thieme-connect.de/DOI/DOI?10.1055/s-2000-7411 |journal=International Journal of Sports Medicine |language=en |volume=21 |issue=7 |pages=459–462 |doi=10.1055/s-2000-7411 |pmid=11071045 |issn=0172-4622|url-access=subscription }}</ref>

* Haldane introduced decompression tables based on five tissue compartments with half times of 5, 10, 20, 40 and 75 minutes.

* The [[US Navy]] refined Haldane's tables and introduced a model with nine tissues. They also introduced calculations for half-times starting from 5 minutes and reaching up to 240 minutes.

Line 135:

==Contradicting work==

Although Haldane's model remains the basis for [[Decompression practice|modern decompression tables]], Haldane's first decompression tables proved to be far from ideal.<ref name=":1" /> Haldane's equation is used by many dive tables and dive computers today, even though, a growing number of decompression models contradict its assumptions such as the

::* Asymmetry of saturation phenomena of inert gases (uptake and elimination),<ref name=":0" /><ref name=":2">{{Citation |last=Rusoke-Dierich |first=Olaf |title=Decompression Theory |date=2018 |work=Diving Medicine |pages=57–79 |editor-last=Rusoke-Dierich |editor-first=Olaf |url=https://doi.org/10.1007/978-3-319-73836-9_9 |access-date=2024-06-04 |place=Cham |publisher=Springer International Publishing |language=en |doi=10.1007/978-3-319-73836-9_9 |isbn=978-3-319-73836-9|url-access=subscription }}</ref>

::* Desaturation according to Hempleman's memorandum and those of Thalmann, taking into account circulating bubbles, VPM, [[Reduced gradient bubble model]].<ref>{{Cite journal |last=Hugon |first=J. |date=2014 |title=Decompression models: review, relevance and validation capabilities |url=https://pubmed.ncbi.nlm.nih.gov/25562945 |journal=Undersea & Hyperbaric Medicine |volume=41 |issue=6 |pages=531–556 |issn=1066-2936 |pmid=25562945}}</ref><ref name=":2" /><ref>{{Cite journal |last1=Doolette |first1=David J. |last2=Mitchell |first2=Simon J. |date=2001-01-01 |title=The Physiological Kinetics of Nitrogen and the Prevention of Decompression Sickness |url=https://doi.org/10.2165/00003088-200140010-00001 |journal=Clinical Pharmacokinetics |language=en |volume=40 |issue=1 |pages=1–14 |doi=10.2165/00003088-200140010-00001 |pmid=11236806 |issn=1179-1926|url-access=subscription }}</ref>

{{clear}}