Decompression sickness during the sinking of a caisson : a study of some factors in the pathogenesis of caisson disease / by H.E. Lewis and W.D.M. Paton.

  • Lewis, H. E.
Date:
[1957?]
Catalogue details

Licence: In copyright

Credit: Decompression sickness during the sinking of a caisson : a study of some factors in the pathogenesis of caisson disease / by H.E. Lewis and W.D.M. Paton. Source: Wellcome Collection.

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    procedures, viz., a fall of 6 lb. rapidly at the beginning of the 30 minutes' period, which could not lead to the loss of any C02 and a fall of 6 lb. rapidly at the end of the 30-minute period, which would lead to a maximum loss of COo (from 3*9% to —- - x 3-9 15 + 6 3.9 2-8 2-8%). This yields a mean figure of = 3*35% C02 as the expected final carbon dioxide concentration at the end of a correctly conducted decompression. It is of interest that a badly performed decom¬ pression, such as in this particular case, should actually have lessened the carbon dioxide accumu¬ lation in the lock. This happened simply because the major fall of pressure in the lock came later than it should have done after an appreciable con¬ centration of carbon dioxide had accumulated. It is in no way a justification for changing the decompression procedure from that already laid down and well tested. To overcome this accumulation of carbon dioxide four measures could be taken, two of them easily. (a) The men could pause for about 10 minutes after the strenuous climb up the ladder, to allow their metabolism to sink back to normal levels. This should help to reduce their carbon dioxide output while confined in the decompression lock, (b) During the decompression the air in the main lock could be flushed out. One way of doing this would be, for instance, to arrange a continuous “ bleed ” of air into the lock, compensated by having the main out¬ let slightly more open than usual. It would be technically difficult, however, to achieve a sufficiently large turnover of air to prevent significant carbon dioxide accumulation. Another procedure would be to raise the pressure by a few pounds every quarter of an hour, and then blow it off immediately. The men would probably feel the effects of these changes of pressure, and would have to be warned accordingly. This procedure, too, would be of limited ventilatory efficiency; if the pressure changes were limited to 5 lb./sq.in., it would not change the air more than once during the decompression, (c) “ Decanting ” is a third measure to be considered. Here, the men leave the blister after a very rapid decompression lasting one to two minutes, and immediately go into a more comfortable chamber where they are very rapidly compressed again and then decompressed at the rate laid down. This method would be hazardous if there were any possibility of delay before entering the comfortable chamber, (ci) If further study showed this to be a serious problem one could easily install a compact blower, operated perhaps by compressed air, circu¬ lating the air through a soda lime system. It might, however, be a fairly elaborate undertaking to secure sufficient clearance of carbon dioxide. (3) Influence of Physical Work.—The influence on the incidence of decompression sickness of the physical work done in making the rapid ascent im¬ mediately before decompression probably manifests itself by creating nuclei for the formation of bends in the men’s muscles. The work of E. N. Harvey and his colleagues (Harvey, 1951) has shown that bubbles do not form in supersaturated solutions unless there is a centre from which the bubble may grow, possibly of the nature of a minute, gas-filled hydrophobic crevice. Damage, or even simple contraction of muscles, is effective in creating nuclei. If practicable, it would be desirable to have a com¬ pulsory rest of 10 minutes before entering the lock. (4) Chilling.—Finally, the chilling of the men is probably a factor more prominent in caisson work than in any other type, simply because the tem¬ perature at the working face of a caisson reaches such high levels. At the top of the caisson itself room is so cramped that it seems difficult to insist on there being dry clothing available for all workers before they enter the blister. But some form of heating installation is in fact recommended by the Institution of Civil Engineers, and this should be insisted upon. The enumeration of these factors is not intended as any criticism of those who sink caissons. The difficulties to be surmounted in such undertakings are considerable and much more work on the medical problems involved is needed. But it is hoped that, by indicating what seem to be the likely causes of disability in this type of work, it may help to reduce the incidence of sickness to levels which allow the working force to function at full efficiency without discomfort and without the risk of consequent serious damage to health. Summary and Conclusions This paper describes some of the factors in the pathogenesis of decompression sickness during the sinking of a caisson. Over a period of three months, there were 89 cases of bends, in a total of about 2,100 decompressions. Among the contributory factors of what was sometimes a rather high rate of decompression sick¬ ness were: (a) inaccuracy in following the decom¬ pression procedure; (b) accumulation of carbon dioxide in the blister lock in which decompression took place; (c) vigorous muscular exercise imme¬ diately before the decompression, due to the ascent of a 70-ft. ladder; (d) chilling because of the con¬ siderable temperature difference between the hot