A brief history of Diving Medicine
By Dr Simon Mitchell
Mid summer, and my job in Oz has taken me away just before that beautiful temperate Kiwi summer weather sets in, and away from the diving that goes with it. I have yet to fully explore diving in the Brisbane area, although I made my first sortie out to Moreton Bay a few weeks back. It was good diving. A perfect day â¦ almost. The next day we were treating a diver off the trip for DCI! Itâs so HOT here. I only have to poke my nose outside for a couple of picoseconds and I am perspiring. I spend a lot of time thinking about showers. But work at the hyperbaric unit is fantastic. We are seeing lots of interesting hyperbaric (non-diving) cases, as well as our share of divers with DCI (about seven cases in two months).
Well, this is number 50. A landmark in Dive New Zealandâs history. There are still a few issues to go to surpass the editorâs age, but 50 is nonetheless quite an achievement. Dave suggested, in view of the âhistoricalâ significance of this issue, that I should write an article on the history of diving medicine. So weâll take a stroll through some of the more interesting aspects of this subject that is inevitably entwined with the history of diving itself.
Diving medicine has its share of colourful stories, many involving great innovators, and others involving ratbags and vagabonds. Obviously I have been proud to add my name to the latter list. Perhaps the first of the great diving medicine innovators was Robert Boyle, the English physicist who gave us Boyleâs Law to agonise over as diving students. In 1667, before âdivingâ was even known, Boyle discovered decompression illness (DCI). He observed that a snake (a âviperâ to be precise) became very distressed when the air was âexhaustedâ from the âreceiverâ in which it resided. This in itself is perhaps not so surprising. Most animals would become agitated if placed in a vaccuum. But Boyleâs additional observation of âa very apparent bubble moving from side to side in the aqueous humor of the eyeâ was more intriguing. This was the first recorded observation of the bubble formation that leads to DCI.
Diving was only in its infancy at this time. Rebreathing from air-filled bags had been tried, but the combined unpleasant effects of hypoxia and CO2 accumulation soon forced the diver to the surface. As a child, I became familiar with this problem after many frustrating attempts to make prolonged observations of the bath plug using goggles while rebreathing from a hot water bottle.
One of the earliest serious attempts at âdivingâ was perpetrated in 1690 by the multitalented Edmund Halley (of comet fame), who constructed a diving bell that was lowered to the sea floor and resupplied with air from weighted barrels! It is reported that this apparatus was used to perform dives as deep as 18 metres for up to 90 minutes. If DCI ever occurred as a result of these adventures, it was never recorded. Indeed, DCI was not described in humans until some 200 years later.
Another pertinent event occurring in the late 1600s was the construction of a pressurised room, or âdomicilliumâ as it was called, by an English physician named Henshaw. This was a well-appointed room, pressurized by bellows, in which members of the gentry could recline and breathe air at a few pounds per square inch above ambient pressure. This, claimed Henshaw, was good for most afflictions of the lungs and bowels, the latter being something that they were particularly fixated on in those days. Although Henshaw could produce little data to substantiate his claims, this was the first recorded therapeutic use of pressure, and the domicillium was therefore the first recompression chamber.
During the 1700s diving technology continued to develop, with English and French engineers independently developing apparatus that allowed diving with air supplied from the surface. However, the limited depth and duration achieved using these devices meant that DCI was rarely, if ever, recorded. In the late 1700s, however, there were developments that finally extended manâs underwater capabilities to such extent that he was able to get himself into trouble. An English engineer called Smeaton perfected a pump that was capable of pressurising a caisson system sufficiently to keep water out and allow meaningful work at depth. A caisson is essentially an upside-down container that sits on the bottom and is pressurised to keep water out. Its occupants can perform work on the sea floor without actually wearing diving dress, although they are under pressure.
This same improvement in air pump technology also paved the way for development of superior surface-supplied diving helmets and suits. Thus, in the early 1800s, there was an explosion in underwater construction and salvage work, and problems began to be recorded. In the early 1840s divers involved in salvage operations on the British warship HMS Royal George reported suffering âcold and rheumatismâ, with the rheumatism almost certainly a symptom of DCI. Around this time, caisson workers involved in bridge construction projects in the USA were suffering more severe forms of the same affliction. 30 out of 352 workers employed in the Eads Bridge project at St Louis were seriously injured (paralysis), and 13 died. These problems in caisson workers gave rise to the terms âcaisson diseaseâ (rarely used today) and âthe bendsâ (which is still commonly employed). Apparently the painful gait of the victims resembled the fashionable âGrecian Bendâ style of walking adopted by ladies of the period.
In 1841 Frenchmen Pol and Wattelle observed that these unpleasant symptoms could be relieved by recompression. In their case, this took the form of returning to work; a unique way of minimizing absenteeism was to get your workers mildly bent! Despite the magnitude of these problems, DCI was poorly understood. Indeed, it was not clearly linked to bubble formation until the 1870s when another Frenchman, Paul Bert, published his 1000-page work La Pression Barometrique, describing a variety of experiments into the physiology of decompression. He showed that DCI was caused by the formation of nitrogen bubbles, finally providing the link between the recently discovered disease and Boyleâs observation of bubble formation in the unfortunate snakeâs eye.
Bert also made several other important observations. First, he suggested that a gradual ascent was likely to prevent the problem; and second, he too noted that pain could be relieved with recompression. Caisson projects of the era began to use recompression in chambers while breathing air, rather than on-the-job recompression, to treat DCI.
The 1870s also saw the first use of a recompression chamber for a non-diving application with any real scientific basis. Until this time, modest degrees of compression had been promoted throughout Europe as therapy for a variety of ailments, and hyperbaric spas rivalled the mineral spas of the era in their promotion as cure-alls. But in 1877, a French surgeon called Fontaine constructed a portable chamber that he towed around with a donkey. He performed surgical procedures inside the chamber with the patient under the influence of nitrous oxide, which he found to be much more effective when administered under pressure. Unfortunately, such rational therapy was the exception rather than the rule, and the tradition of quackery in hyperbaric medicine was maintained until well into the present century.
Indeed, as recently as 1937, an entrepreneurial type named Cunningham based in Cleveland, Ohio was operating a 72-room Hyperbaric Hotel, in which guests stayed under pressure for varying periods, for the unsubstantiated âtreatmentâ of a vast array of problems. Thankfully, the emerging importance of recompression in treatment of DCI gave the hyperbaric discipline a credibility lifeline until new valid non-diving uses were found in recent times. But back to diving.
In 1906, concerns over the incidence of DCI drove the British government to commission John Scott Haldane, a Scottish physiologist, to investigate preventative strategies. Following up on Bertâs observation that slower ascents prevented the problem, Haldane and his co-workers used goats to test various decompression protocols, resulting in the publication in 1908 in the Journal of Hygiene of the first set of true decompression tables for diving. The tables revolutionized diving safety, with the incidence of DCI dropping wherever they were used. These tables, and the physiological principals underpinning them, have formed the basis for many subsequent modifications and developments up to the present day.
Perhaps the next pivotal event in the development of diving medicine was the use of oxygen during recompression in the treatment of DCI. Until the mid 1930s, recompressions had been conducted with the patients breathing air; pressure alone was the therapeutic modality. Oxygen had been discovered in 1775 by Joseph Priestly, who named it âdephlogisticated air,â and its potential therapeutic effects were recognised soon after. Indeed, Bert in the late 1700s specifically suggested that it might be beneficial in treatment of DCI. Unfortunately, oxygenâs toxic effects at higher pressure were recorded not long after its discovery, and the use of hyperbaric oxygen as therapy was generally discouraged. It was not until 1937 that it was used with any regularity. It was soon established that a treatment depth of 18 metres of sea water (2.8 atmospheres) was the maximum depth at which routine recompression treatments could be conducted using oxygen, without an unacceptably high risk of toxicity. The treatment protocols in use today were established in 1965 and, remarkably, have not changed since that time.
In any account of the history of diving medicine it would be remiss not to mention the invention of scuba equipment by Jacques Cousteau in 1943. The subsequent popularisation of diving (mainly since the 1960s) fundamentally altered the face of the patient population presenting with DCI. Decompression illness in recreational divers has become far more common than in commercial or military divers, and is clinically challenging for many reasons. Most importantly, recreational divers often present with the milder forms of DCI after long delays, and an unacceptably high proportion of them fail to make a complete recovery. Obviously, we cannot be complacent about our ability to successfully treat DCI, and improved strategies must be sought. Future developments are likely to involve the use of gases other than oxygen (such as oxygen-helium mixtures for recompressions deeper than 18 metres) and drugs. To date, little progress has been made towards identification of drugs likely to be useful in the treatment of DCI, although recent developments in our own work at Auckland may have taken us a step closer.