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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    Fig. 3.—Frequency of bends in various parts of the body (hatched columns indicate bilateral involvement). (2) Vitiation of Air by Carbon Dioxide during Decompression.—Also shown in Fig. 4b is the rise of carbon dioxide percentage during the progress of the decompression. It has also been drawn in terms of the absolute tension of carbon dioxide, since it is this that is physiologically important. The absolute tension reached a maximum of 2-63% atmosphere after the decompression had been proceeding for 18 minutes. Thereafter it fell, although the per¬ centage of carbon dioxide in the air in the lock continued to rise. The differing time course of the two measures of carbon dioxide is due, of course, to the changing lock pressure. It is possible to make an approximate calculation from these figures of the total carbon dioxide pro¬ duction during the period of decompression. In doing this, it is necessary to include in the calculation the carbon dioxide lost in the gas vented from the chamber. When this calculation was made, knowing the capacity of the chamber to be 69 cu.ft., and allowing about 10 cu.ft. for the volume occupied by the five men themselves, we obtained a carbon dioxide production of approximately 0-51. per minute, corresponding to an oxygen consumption of about 0-6 1. (3) Exercise.—It was found during the last war that vigorous exercise was a factor precipitating de¬ compression sickness in aviators (Cook, 1951). The evidence for this is much weaker for decompression sickness resulting from exposure to high pressures, but it remains a possibility. It has been noticed in diving experience, for instance, that bends tend to occur in those muscles which have been most heavily worked during exercise. We believe it to be significant, therefore, that at the end of the shift the men had to climb a 70 ft. vertical ladder in order to reach the decompression lock. This ascent was usually made as fast as possible, and there was no waiting period before decompression began. Thus the decompression took place immediately after severe exercise, and this exercise may well be an important contributory factor to the incidence of bends. (4) Chilling.—During the work at the bottom of the caisson the men are usually exposed to con¬ siderable heat. This is particularly the case on a warm day, or when concreting is done, since the setting of concrete is an exothermic reaction. On the other hand, when they come into the decom¬ pression chamber, the fall in pressure during de¬ compression is associated with a considerable cooling of the atmosphere in which they are placed. This means that not only is the air around them cold and humid, but there is considerable condensation of moisture on their clothes, so that these, already damp, may become thoroughly wet and chilly. Experienced workers sometimes keep a set of dry clothes in the decompression chamber into which they change while waiting. The medical orderlies recorded the impression that men who were not careful about dry clothes or who found the decom¬ pression uncomfortably cold were those who seemed to be liable to decompression sickness. Discussion In many respects the decompression sickness observed during this undertaking resembled that seen during the construction of a tunnel (Paton and Walder, 1954). Thus it had an “ epidemic ” charac¬ ter; individuals varied considerably in their suscepti¬ bility; and the incidence in different parts of the body was more or less the same as that observed in tunnel work. On the other hand, the incidence was somewhat higher than has been recently recorded in tunnel work. It is probably important to recognize certain differences between the two types of under¬ taking. In the first place, the construction of a