- The Bends: Compressed Air in the History of Science, Diving, and Engineering
The story of the use of compressed air for tunneling under rivers, for placing the foundations of large bridges, and for commercial and recreational diving is a fascinating one. John Phillips nicely describes the development of the first caissons (vertical shafts with compressed air that enable the piers of bridges to be set), and goes on to relate the formidable engineering and medical problems associated with building some of the great early bridges (including the St. Louis Bridge over the Mississippi River, built by James B. Eads, and the Brooklyn Bridge in New York, built by the Roeblings, father and son). The mysterious disease of decompression sickness occurred when the workers emerged from a period in compressed air; because the pain caused them to adopt a stooping attitude, the victims were said to have the “Grecian bend,” named after the posture of fashionable ladies wearing large bustles in the mid-nineteenth century.
Decompression sickness caused an enormous amount of disability and not a few deaths as the commercial pressures to build large bridges and tunnels increased toward the end of the nineteenth century. We now know that the cause is nitrogen bubbles in the blood and tissues, but the mechanism proved remarkably elusive, even though Paul Bert recognized the basic cause in his monumental book of 1878, La pression barométrique.1 It is disturbing that Bert’s work, and also the fundamental studies of J. S. Haldane, who introduced staged decompression to prevent bends, took so long to be recognized by industry. An interesting sidelight is that when it was realized early on that the best treatment for the symptoms of decompression sickness was to recompress the men at a somewhat lower pressure, some people drew an analogy with homeopathy.
Although this book makes interesting reading, it is marred by a number of scientific errors. For example, on page 201 it is stated that hyperbaric oxygen therapy at two or three atmospheres can raise the blood oxygen content ten times higher than normal—but in fact, because hemoglobin is normally almost fully saturated with oxygen, the increase is only about 30 percent. On page 20 we read that “air really doesn’t have ‘weight’ at all”—quite the contrary: we weighed it in high-school physics by filling an evacuated bulb on a balance. On page 167 Phillips states that nitrogen is “the active component in all inhaled anesthetics”—not so, and even if it were, this would not be the reason for the narcotic action of nitrogen. On page 192 he erroneously implies that amniotic fluid is the source of lung surfactant; and on page 204 he states that hyperventilation causes “base accumulation,” whereas the opposite is true.
Apart from these factual errors, the book is of limited value to someone with a serious interest in history. It is almost entirely based on secondary sources, and [End Page 512] when primary sources are cited, as in the quotation from Boyle on page 23, there are inaccuracies. Without belaboring the historical errors, it is not true that “as the seventeenth century closed Robert Boyle and Robert Hooke discovered the laws governing the sea of air” (p. 10); Boyle’s work on the “spring of the air” was first published in 1660, not 1680 (p. 20);2 and the figure caption on page 113 about the flight of the balloon Zénith is misleading: Bert did not sponsor the voyage (he did not hear about it until it was too late to recommend adequate oxygen supplies), nor did the tragedy send him into the laboratory for the “careful, quantitative animal experiments which would revolutionize baromedicine” (Bert’s main work was done before the flight of the Zénith).
Many parts of this book are enjoyable to read, but it is important to point out that it is not an authoritative account.
1. Paul Bert, La pression barom...