- Haldane: update on its work
- Haldane: often quoted… but visibly little read!
- Short biography of the authors
- When was the request from the Royal Navy?
- What is the date of publication of Haldane's tables: 1907 or 1908?
- Haldane tables, what depth max. ?
- False information on the Haldane tables at 100m, whose fault is it?
- Haldane tables, fast ascent rate?
- Paul Bert n'a jamais publié de tables de plongée
- Challenge posed to Haldane
- Analysis by Haldane
- Haldane tables
- In conclusion
Haldane: often quoted… but visibly little read!
A simple consultation on the web makes it possible to realize that Haldane is often quoted wrongly or inaccurately, which poses difficulties for diving instructors (what to believe?), further difficulties for MF2 candidates in their preparation for the exam (What to learn?):
- Haldane would have published 3 tables, one of which allows diving to 100 m.
- He would not have published the first dive tables, it would be the work of Paul Bert.
- He would have established the principle of rapid lifts!
- Il aurait “inventé” que le rapport de pression ne doit jamais dépasser 2:1.
- The Royal Navy's request for these dive tables dates back to 1903, 1905, 1907...
- The publication would date from 1906, 1907, 1908 …
- As for the list of hypotheses he would have retained (a question sometimes asked such as in the written test of the MF2), they are more or less sourced and more or less fanciful depending on the websites, articles or memoirs. According to some he would have retained 4 hypotheses, according to others it would be 5, 6 or 7 hypotheses...
Let's take stock of the question.
Starting with the authors of this founding article (excerpt from their biography published in the French translation:Prevention of decompression sickness, 2008.). Connaître leur histoire et leur parcours est essentiel à la compréhension de leurs travaux et des raisons qui ont fait qu’ils se sont retrouvés dans “the adventure of the first dive tables“.
By Alain FORET (BEES2/DESJEPS), translator ofThe Prevention of Compressed-air Illness, 100-page scientific article written by AE BOYCOTT, GCC DAMANT and JS HALDANE, published in English in 1908 inThe Journal of Hygiene(Cambridge University Press).
Short biography of the authors
When was the request from the Royal Navy?
The letter from the British Admiralty asking Haldane to work on the subject of decompression is dated August 8, 1905. It is reproduced below, removing any ambiguity and closing any debate on the matter.
pp4-haldane-amirauteWhat is the date of publication of Haldane's tables: 1907 or 1908?
The (confidential) report to the Admiralty dates from August 1907. The first official publication, accessible to all, dates from 1908 in theJournal of Hygiene. As a result, the date chosen is 1908, that of 1907 referring to a confidential document.
Haldane tables, what depth max. ?
Haldane has never published 100m tables.
Two tables have been published, one for dives of "normal" duration [maximum total ascent time: 33 min.], the other for dives "beyond normal duration" [total ascent time ascent: from 42 to 238 min.]
These tables calculate a desaturation up to 62 m. This 60 m limit was not imposed on Haldane by narcosis but by the power limit of the pumps supplying the divers and by the Royal Navy's letter of mission of 1905 ("(a) Improvements to enable men to dive in 30 fathoms of water…” – 30 fathoms [fathoms] = 55 m, he went up to 34 ftm = 62 m).
False information on the Haldane tables at 100m, whose fault is it?
Our research has made it possible to find the text at the origin of this error, then reproduced from author to author without verification, including in prestigious North American diving magazines.
The chapter in question (everyone can make mistakes) is written by HV HEMPLEMAN inThe Physician's Guide To Diving Medicine, Plenum Press, New York, 1984.
L’auteur y écrit, page 237, que Haldane a publié trois tables différentes dont une pour les plongées profondes jusqu’à 100 m de profondeur : “Haldane issues three separate air diving tables. The first table was for all those dives requiring a decompression time of less than 30 min. The second table was for all air dives requiring a decompression time of more than 30,min. and the third table was for deep air to depths of 330 ft (100 m).” On s’attend alors à la publication de ces 3 tables dans les pages suivantes. Mais l’auteur n’en publie que deux, en pages 239 et 240, celles de Haldane que nous connaissons. Et pour cause : Haldane n’a jamais publié de tables à 100 m.
Haldane tables, fast ascent rate?
Those who say Haldane offers a fast ascent rate mean:a faster speed than today, do not include the historical context (and probably did not have access to these tables).
In reality, Haldane's tables, by creating ascents in stages, make it possible to ascend faster than a slow and uniform ascent at 0.5 m/min (Heller, Mager and von Schrötter as well as Paul Bert) or at 1 m /min (Denayrouze). This also corresponds to the Admiralty order, judging the speeds of 0.5 to 1 m/min totally unsuitable in an operational context. Consider that this meant, at 0.5 m/min, an ascent time of one hour from 30 m, regardless of the time spent at the bottom!
At Haldane, the ascent speed is around 10 m/min with a variation depending on whether you dive more or less deep (faster for deep dives, slower when approaching the surface), this which is a still relevant approach to the ascent rate:
- 6 to 8 m/min up to 20 m deep. max. ;
- 10 m/min for dives between 40 and 20 m deep. max. ;
- 10 to 14 m/min for dives between 60 and 40 m deep. max.
Haldane a donc proposé des remontées à une vitesse supérieure aux vitesses en vigueur à l’époque (0,5 à 1 m/min), mais il ne propose pas une vitesse “rapide” au sens où on l’entend aujourd’hui. Bien au contraire, il propose une vitesse de l’ordre de 10 m/min, ralentie à 6/8 m/min à l’approche de la surface, ce qui correspond très exactement aux vitesses préconisées actuellement, en particulier depuis le symposium international organisé dans la ville Costa Mesa (Californie) en 1990 par l’American Academy of Underwater Sciences. Under the titleBiomechanics of Safe Ascents, the conclusions recommend, for leisure dives, an ascent speed of the order of 10 m/min, translated into operational form as a speed that can range from 9 to 12 m/min (Learn more). This speed has been adopted worldwide.
Paul Bert has never published dive tables
Contrary to what some authors indicate (we do not know their reasons because they do not cite any precise source), Paul Bert never published dive tables. Reading his bookbarometric pressure de 1878 aux éditions Masson le démontre. En fait, Paul Bert se contente de proposer une remontée “suffisamment ralentie” et de donner quelques conseils après avoir mis en évidence le rôle de l’azote dans les accidents de désaturation.
Paul Bert recommends the following preventive measures:
"As soon as the pressure used reaches 2 atmospheres in total pressure, it will be good to watch closely; there is as yet no real danger, but local pains are already appearing, and it is useful, moreover, to accustom the workers early to precautions. However, the great precaution, it is the slowness in the decompression. I think that between 2 and 3 atmospheres, it will be necessary to devote, to be completely sheltered, half an hour to decompression; from 3 to 4, one hour […].
When [the divers] come back from the deep sea, by 30 meters for example, it is absolutely necessary, either to put them back on some seat which allows them to be held for at least a good quarter of an hour halfway, or to force them to park for a sufficient time on some shoal, when there is any within the extent of their fishing ground.
Si enfin, malgré ces diverses précautions, un accident survenait, que faire ? […] Si l’auscultation dévoile quelques gargouillements gazeux dans la région du cœur, se hâter de faire respirer de l’oxygène aussi pur que possible, qu’on devra toujours avoir dans un ballon de caoutchouc, ou mieux, comprimé en quantité dans quelque réservoir en acier. Puis, lorsque les gaz auront disparu du cœur, et que la mort ne sera plus imminente, soumettre aussitôt le malade à une pression supérieure à celle d’où il sortait, pour le décomprimer ensuite avec une lenteur extrême. Du reste, quand la pression atteint 4 atmosphères, il serait prudent de faire respirer de l’oxygène […] aussitôt après le retour à l’air libre, et sans attendre l’apparition d’aucun accident. Lorsque la dépression manifestera ses effets par la paraplégie, il faudra immédiatement recomprimer, sans perdre son temps à faire respirer l’oxygène, surtout quand l’accident n’est arrivé que quelque temps après le retour à l’air normal, car il ne s’agit plus là d’obstruction générale de la circulation pulmonaire, mais de quelque bulle de gaz arrêtée dans les vaisseaux de la moelle, et dont il faut réduire aussitôt le volume pour que le sang puisse l’entraîner. "
Paul Bert préconise ainsi de limiter le temps de séjour au fond et d’adopter une vitesse de décompression “suffisamment ralentie”. Il reste dans une logique de remontée lente et uniforme. Même s’il envisage un arrêt dans l’eau, par exemple à demi-profondeur, il ne formalise ni la notion de “paliers” ni celle de “tables de décompression”.
Challenge posed to Haldane
Pour Haldane, le principal défi est de trouver un autre moyen qu’une “décompression lente et uniforme” afin d’éviter le risque de formation de bulles pathogènes à la remontée. En 1905, c’est la seule solution proposée :
- Hill and Greenwood successfully ascended 50 m to the surface at a speed of 0.5 m / min (Heller, Mager and von Schrötter), for an ascent time of 1h40.
- Paul Bert recommends a "sufficiently slowed decompression", of the order of 30 minutes for a dive to 20 m (0.6 m / min) and one hour for a dive to 30 m (0.5 m / min). .
- Denayrouze recommends an ascent speed of 1 m / min, with a limitation of dives to 35 m depth for a maximum duration of 2h30 at the bottom.
This approach is not satisfactory because:
- it makes the ascents so long that it effectively prohibits deep dives (in 1905, it was a military objective for theRoyal Navy);
- it imposes the same duration of ascent whatever the time of exposure to the bottom, even though it has already been proven at the time that the risk of accident increases with the duration of exposure and remains low for short exposures .
However, the mail from theRoyal Navyof 1905 is unambiguous: by creating a commission on deep diving, it wants a reliable and operational solution to be found for dives down to 55/60 m. Haldane must therefore be innovative and find another process.
Analysis by Haldane
At first, Haldane fights, on a scientific level, the very principle of slow and uniform ascents: "To avoid the risk of bubble formation during decompression, it was recommended until now that it be as slow and uniform as possible.. "He shows that, for deep dives, a"uniform decompression at this rate, already dangerous for goats, would no doubt be extremely dangerous for humans, who desaturate significantly more slowly than goats".
Ratio 2:1, a notion widely accepted by all at the time. He took it up and extended it, but he did not create it.
Haldane then attempts to find a new method of decompression (desaturation). His reflection is based on an observation unanimously shared at the time, including by Paul Bert: “Those who have experience of working in compressed air are well aware that there is no risk of chamber sickness, even with a very rapid ascent, provided that the pressure reached does not exceed a certain value. It seems perfectly clear that no symptoms appear when the relative pressure is less than one atmosphere.[10 meters deep], regardless of the duration of exposure. In other words, Haldane finds that it is possible to go from 2 bars (10 m depth) to 1 bar (sea level) without risk whatever the duration of exposure.
He will then extend this reasoning to all depth zones: “Therefore, it seems likely that if a sharp decompression from two atmospheres absolute to one is safe, so must four atmospheres absolute to two, six atmospheres absolute to three, etc.. Our experiments, described in detail later, have shown this to be the case. The desaturation process can, therefore, be greatly accelerated by rapidly reducing the absolute pressure by half, and by ensuring that, for the remainder of the decompression, saturation in any part of the body can never reach more. double the air pressure. The main advantage of this method is that, from the start of decompression, the elimination of nitrogen from the tissues takes place at the highest possible speed without danger.. "
Haldane thus leads to the creation of the rise in stagestaking into account the pressure and the duration of exposure to determine the depth and the time of the stages:
"This method greatly simplifies the problem of decompression safety, and removes many practical difficulties, especially with regard to deep diving. It can be called a method ofdecompression in stages, and it is described as such below, although its essential characteristic is not that the decompression is carried out in stages, but in that it is rapid until the absolute pressure is halved. and then continued slowly. "
Haldane tables
HALDANE_TABLESPresentation
- They calculate a desaturation up to 62 m (contrary to what is widespread on the web, Haldane has never offered tables up to 100 m). This 60 m limit is not imposed on Haldane by the narcosis but by the power limit of the pumps supplying the divers and by the mission letter of theRoyal Navyfrom 1905 (“(a) Improvements to enable men to dive in 30 fathoms of water…” - 30 fathoms [fathoms] = 55 m, it went up to 34 ftm).
- Two tables have been published, one for dives of a "normal" duration [total ascent time: 32 min.], The other for dives "beyond a normal duration" [total time of ascent: from 42 to 238 min.]
- The ascent rate is around 10 m/min with a variation depending on whether you dive more or less deep (faster for deep dives, slower when approaching the surface), which is a always up-to-date approach to the ascent rate:
- 6 to 8 m / min up to 20 m deep. max. ;
- 10 m / min for dives between 40 and 20 m deep. max. ;
- 10 to 14 m / min for dives between 60 and 40 m deep. max.
The 10 hypotheses adopted by Haldane
Many websites disseminate approximate (or even false) information regarding Haldane's assumptions. In order to clarify this point, here10 hypothesesretained by Haldane, with reference to the page number corresponding to the original publication of 1908 inThe Journal of Hygiene.
- In the lungs, excess nitrogen is transmitted instantly to the blood (p. 345).
- In the lungs, during decompression, with each circulatory cycle, the blood instantly transmits to the lungs the proportion of excess nitrogen it contains (p. 351).
- In the tissues, excess nitrogen is transmitted instantly (p. 345).
- The partial pressure of nitrogen in alveolar air is the same as in inspired air (p. 345).
- Tissues are all similar in constitution to blood except fat, which it treats differently (p. 346).
- A circulatory cycle takes place in 1 minute (p. 348).
- The desaturation curve mirrors the saturation curve (p. 350).
- The pressure ratio should not exceed 2: 1 (p. 357). This would correspond today to setting a Sc = 2. Haldane sets a unique Sc for all compartments.
- The nitrogen charge and discharge phenomena in the human body can be summarized in 5 compartments (dummy anatomical regions) whose periods (half-life) are: 5, 10, 20, 40 and 75 minutes (p 363).
- Descent time is included in dive time (p. 367). The virtual exposure time considered is the actual background exposure time, increased by half the descent time (p. 350).
Other contributions from Haldane
Beyond the creation of stepwise decompression, Haldane makes various very interesting observations throughout the publication:
- He recommends moving the arms and legs at the landings in order to prevent the conditions of desaturation from being very different from those of saturation (p. 367);
- Age and overweight appear to favor accidents (p. 368);
- The ascent rate of around 10 m / min is determined empirically (p. 370);
- It discusses the notion of factors specific to each individual and variables from one day to the next that may contradict the decompression model [we speak today of contributing factors] (p. 384);
- It signals the presence of bubbles without symptoms (p. 411) [today we speak of “silent bubbles”].
In conclusion
Haldane's work is still relevant today.
He laid down the main principles of desaturation, which are still in force. Without taking anything away from the work of his successors, they improved the initial model in its calculation methods but without changing its fundamental principles.
As such, Haldane remains the founder of the desaturation theory alongside Paul Bert who showed the role of nitrogen in the mechanism of ADDs.
Access to the original publication (Journal of Hygiene, 1908) in English:Click here.
Access to the presentation page of the French translation (Alain FORET, 2008, for the 100th anniversary of the original publication):Click here.
Download original Haldane tables:Click here.
Text Copyright Alain Foret – Reproduction prohibited without the written authorization of the author.