Questions have been asked in Parliament about an increase in decompression experiments involving goats and other animals. Simon Rogerson reports on the bizarre and secret world of hyperbaric research, and the debt owed by today’s recreational divers to the animals who died in the chamber

Goats are ‘ideal’ for hyperbaric experiments, pigs have a physiology very similar to that of humans, and are also used. Baboons get very bad-tempered and are prone to fighting in chambers. Rats are used to establish gas toxicity. Pictures from Oxford Scientific Films.

Even though Royal Navy divers are equipped with the most comprehensive set of diving tables available, the Ministry of Defence persists with animal experimentation on a vast scale. Over the past five years, more than 700 goats have been tethered in purpose-built decompression chambers and subjected to diving profiles that have often resulted in the collapse of vital organs. The experiments are being carried out by the Defence Evaluation and Research Agency (DERA), to determine the pressure and time limits for the safe escape from submarines at depth.

A recent report prepared by the Animal Welfare Advisory Committee of the MoD revealed that a restocking programme has been started at the Centre for Human Sciences in Alverstoke, Hampshire because many of the goats used in the experiments there are now too old to be subjected to great pressures. ‘Goats may be used several times in a series of studies to evaluate the effects of decompression after a simulated dive,’ the report states. ‘The experiments are carried out on land in a hyperbaric chamber.’

Portsmouth South MP Mike Hancock has voiced protest in the House of Commons, arguing that the experiments are simply uneccessary. ‘They must be taking the goats to near-death,’ he said. ‘We can only deduce that these animals are suffering terrible pain. This technology has been with us for a long time and I simply cannot believe we still need to carry out these experiments.’ In a letter to Hancock, the chief executive of DERA, Sir John Chisholm, said goats are being used as the experimental model for decompression research because their physiology is similar to that of humans.

A spokesman for DERA said the organisation was conducting the research in order to see how much pressure could be endured while exiting submarines at depth: ‘The current work will lead to improved operating procedures for submariners which will enhance their chances of survival in the event of an accident. It will also add to the knowledge of decompression sickness and its treatments, which will be of practical benefit to commercial and recreational divers.’

According to the submarine project manager, the nature of pressure exposure in submarine escape is new territory in decompression research, and medical ethics demand that the Navy should get an understanding of the true risks by using an animal model. ‘Some may argue that the only valid model would be a large primate,’ he said. ‘However, previous work by DERA and other laboratories has shown that a human-sized farm animal gives results that are close enough for practical purposes.

‘For those animals which do experience decompression sickness, they undergo the same recompression therapy as a diver, and the vast majority make a complete recovery. Animals are destroyed for humane reasons only when necessary. The animal programme is relating the responses of the animals to those expected in man and is also focused on increasing our understanding of the underlying pathology, which will lead to improved prevention and treatment measures for all at risk of decompression sickness.’

Use of animals in the study of decompression illness dates back as far as 1670, when the scientist Robert Boyle first described its effects. Using the recently-invented vacuum pump, he decompressed a snake and reported: ‘I once observed a viper furiously tortured in our exhausted receiver ... that had manifestly a conspicuous bubble moving to and fro in the waterish humour of one of its eyes.’ So, pretty much as soon as it was technologically possible to subject an animal to increased pressure, scientists were investigating the issue on a ‘let’s see what happens’ basis.

‘We can only deduce that these animals are suffering terrible pain ... and I simply cannot believe we still need to carry out these experiments’ Mike Hancock MP

At the beginning of the 20th century, the renowned physiologist John Scott Haldane was appointed by the British Admiralty to develop safer decompression tables for use by Royal Navy divers, in order to reduce the common occurrence of DCS attacks suffered by the men. Haldane experimented with goats in a recompression chamber, keeping them at high pressures for periods of up to two hours. Although several died during the experiments, he discovered that they could be decompressed to an ambient pressure half that of what he believed the level of saturation to be, before displaying obvious signs of decompression sickness.

Nick Baker of the Historic Diving Society is currently working on a biography of Captain G Damant, the Royal Navy’s First Head of Diving, who collaborated with Haldane at a time when he was proving his theory of staged decompression. ‘It was Haldane’s innovative thinking that brought us the idea of a staged ascent that would lead to the dissipation of nitrogen from the bloodstream,’ he said, ‘A great many animal experiments were carried out using goats at Chelsea’s Lister Hospital, where there was a large decompression chamber. They would have preferred using pigs, which are physiologically closer to humans, but in those days there were fewer pigs and a lot more goats around London. Goats were basically the second choice, but quite close to humans in terms of respiratory physiology. Experiments carried out to confirm Haldane’s theory form the basis of every decompression table available today, from the BSAC’s own tables to algorithms in computers.’

Animal farm: above, a cross-section of Siebe, Gorman and Co’s research and experimental department, complete with poison gas chambers on the far left; right, top, most experimental programmes start with small laboratory animals, such as this rat, which is being placed in a purpose-built mini-chamber; right, a committed researcher and scientist, Professor JBS Haldane (on right) often entered the chamber himself during experimental work; below right, looking tentative, a ‘survivor’ goat hesitates before leaving the chamber; below left, pigs and goats are the preferred subjects for hyperbaric research, because their physiology is similar to that of humans

Damant and Haldane were involved in a series of hyperbaric experiments carried out by Siebe, Gorman and Co in 1920, using mixed gases such as helium and oxygen. The company’s laboratory in Westminster Road, in London, was long held to be the spiritual home of British diving. During one of these experiments, a goat was decompressed to a pressure of about 60m using Heliox. As it reached the end of its decompression, pure oxygen was fed into the chamber so that the final decompression could be speeded up. By this point, the goat was getting hungry and had spotted two wires at the top of the chamber. These should have been attached to a light bulb, but it had been removed for some reason, and the wires were simply taped together. What the researchers didn’t know was that they were also live. So when the goat began to nuzzle and then chew at the wires, it made electrical contact. There was understandable panic when the scientists saw electrical flashes through the observation port, and they all leaped under a table. Damant later confided in his journal that he had fully expected the chamber to explode, sending shrapnel across the room at high velocity. But, in an extraordinary piece of good fortune, the rubber seal around the chamber door burned away first, and the door was blasted off by a sheet of flame that shot across the room. The researchers all remarked on the heavy whiff of roast goat in the room. When the chamber had cooled, they were greeted by the carbonised shell of the goat, its teeth still clamped around the wires that had been its undoing.

The dispassionate attitude towards animal experimentation in the earlier half of this century is summed up quite elegantly in Robert H Davis’ seminal tome, Deep Diving and Submarine Operations. On deep diving experiments, he wrote: ‘So as to avoid unnecessary risk to human life, it is our practice, before testing any new system of deep-diving or decompression on men, to make preliminary tests on animals.’

The most reluctant experimental subjects are baboons, which truly resent being confined in chambers, and scream furiously when incarcerated. Davis recalls that the baboons used by Siebe, Gorman and Co made every attempt to escape their fate, including one that climbed to the roof rafters and refused to be tempted back to the chamber by offerings of food. ‘At a pressure equal to 400ft (122m) of water, these animals found the floorboards of the chamber movable, and pulled them up with the greatest dexterity,’ Davis reported.

Davis’ gentle irony belies a different side to his nature, a steadfast devotion to research over all other concerns that is perhaps shared with other scientists involved in hyperbaric research. During a lecture for the Royal Society of Arts, he provoked anger by suggesting that convicted murderers awaiting execution should be given the option of participating in extreme decompression experiments. ‘We feel that if such criminals were given the choice between certain execution and a chance of surviving the scientist’s experiment, very few would refuse to take the risk,’ he argued. ‘While expiating their crimes, they would be helping the progress of research, and some of them might even be the instruments of such far-reaching discoveries for the benefit of suffering humanity as to warrant their inclusion among the saints – in the scientific sense.

Numbers of animals 'humanely' killed by DERA

Although Haldane’s theory provided divers with a safe set of dive tables, researchers have never stopped trying to find ways to chip away at the limits, allowing divers more time underwater. Also, a variety of animals have been used to carry out research on the effects of diving when pregnant, to ascertain whether or not bubbles form within a foetus after inadequate decompression. In 1968 a study was conducted in which 28 pregnant dogs were compressed to 6ATM and exposed for between one and two hours. Although all the mothers suffered severe bends, none of the foetuses died. Another experiment involved causing decompression sickness in sheep which were late in pregnancy. It concluded, somewhat predictably, that mothers who had the bends immediately before delivering gave birth to stillborn lambs.

The whole notion of using animals for supposedly sophisticated experiments is often questioned by eminent scientists. In his influential book, Deeper Into Diving, John Lipman says the problem with such experiments is that no animal model can really replicate what happens with humans. Rats and dogs have a more efficient way of transferring gas to and from the foetus than humans, but scientists now believe that sheep are the best subjects for experiments involving pregnancy, as their placentas closely resemble the human one.

A campaigning group, Animal Aid, is convinced that scientists have carried out more than enough hyperbaric experiments on animals this century, and that the military in particular should be subject to greater controls. ‘Time and time again we find that using the animal model is a bogus exercise, because of the fundamental differences between them and us,’ said Animal Aid spokesman Andrew Tyler. ‘There is a hell of a lot of actual and anecdotal evidence out there, so why do more and more goats have to go into these chambers. People just want to say they have conducted experiments, but they don’t seem to care about the reliability of the experiments. So they resort to using animals, and then act surprised when they get useless data.’

The reality of decompression sickness is that it is often so hard to diagnose that even respected specialists can make mistakes. Five US Navy doctors were present during a 1969 chamber dive in which a diver complained of a problem with the sole of his foot after a dive to 30m. Recompressed to 6m, the pain travelled to his ankle. Another 3m and the pain was in his calf. The chamber was pretty soon at 160m, with the problem of an exhausted man who was cramping everywhere and complained of his entire body being painful.

‘With the concurrence of the doctors I decided to give him two aspirins,’ one of the medical officials present recalled. ‘The guy then got into his bunk and 10 minutes later he was deeply asleep. Eight hours later, he woke up; the pain had disappeared and when he arrived back at the surface six days later he was okay. Now, I don’t know what happened there, but I say that from time to time we don’t know what’s going on. I’m pretty sure it was not a bubble problem but certainly lactic acid.’

In an ironic twist, hyperbaric technology is now being used to treat pets in America. A company called Oxytec has manufactured the first veterinary hyperbaric oxygen chamber for small animals. They claim the treatment delivers more oxygen to the tissues of the ‘patient’, promoting the body’s ability to kill germs, speeding recovery. The treatment has yet to enter mainstream veterinary practice, but there is at least now a possibility that animals may finally benefit from recompression research.