To drive 380 miles from my home in Norfolk seems like a heck of a long way to go to do one dive and not even get wet. That is exactly what I did this weekend to join the lads and lasses of DiveFun for a pot dive at the Diving Disease Research Centre (DDRC) in Plymouth. We were going to experience the effects of increased pressure in one of the biggest hyperbaric chambers in the UK. Most divers only get this close to a chamber after suffering the effects of decompression illness. We were making the visit to learn more about the fascinating work carried out by the DDRC which we were to discover has a much wider application than treatment of divers with suspected DCI.
The DDRC is a registered charity which has not one but three hyperbaric chambers. We were to dive in the largest of these to an effective depth of 40 metres. The 12 intrepid DiveFun members spilt into 2 groups of six. Arnie, myself and Russ together with three members of the Downer family, Brian, Adam and Matt were in the first group and were being taken by our DDRC attendant, Matt. The second group who would dive with Sally, consisted of Steve, Dickie, Joe, Richard, Virgina and Pauline,
they watched a diving safety video while we prepared for the dive.
Fire precautions are essential with any hyperbaric chamber. All our clothing had to be cotton and not man made fibres in case of static. We also had to remove everything from our pockets for the same reason. Nice blue overshoes also had to be worn to avoid us trampling dirt into the chamber. We did take our dive computers, which were placed in a bucket of water to maintain wet contacts. 
Matt briefed us on the importance of equalising regularly during the descent phase and to signal any discomfort so the rate could be slowed or stopped if necessary. The safety briefing also included what not to touch and the effects of blowing the chamber down to depth. The first of these was noise. It takes a lot of air to increase the pressure to 5 bar, this comes in through filtered valves and the noise produced means that ear defenders are a must. Also anyone who has had a cylinder filled knows that it becomes warmer as pressure increases (the General Gas Law), exactly the same thing happens at the larger scale of a chamber as we were about to discover.
At all times Matt was in contact with his supervisor Patrick and colleague Sally who were at the controls of the chamber. After dishing out boiled sweets and ear defenders we were almost ready to go. The last task was for us each to blow up one of the small balloons given to us. The noise during the descent was really intense, even through the ear defenders, the pressurised air also caused condensation to form which gave the impression of sitting in a large noisy steam bath. The temperature rose from around 21 to 36 degrees centigrade in the two minutes it took to reach depth. It was like being suddenly dropped in a tropical rain forest. At this stage the balloons that were fully inflated at the surface had shrunk to the size of tennis balls (Boyles' Law).
At the prescribed depth, Brian made a comment and we suddenly realised that we had evolved from burly, hairy arsed divers to a troupe of chipmunks as the increased pressure played havoc with our vocal chords. The sight of a large bloke talking like Pinky & Perky has to be experienced first hand to get the true effect. Not only that but the nitrogen narcosis had us giggling like school girls every time somebody spoke. 
Matt called things back to order by distributing 6 clipboards and pens with a ten question 'hyperbaric intelligence test' which we were to fill in within 4 minutes. Most of these brain teasers and simple sums would have been straightforward on the surface but at this depth with narcosis taking full effect they could have been joke books or comics for the amount of hilarity we were experiencing. The next task was to blow up a balloon each at depth to see the effect as the pressure was reduced again. At this stage there was some amusing discussion regarding the positive effect of pressure on an erection but as we were all to stupefied to make the necessary preparation (divers droop?), this particular experiment had to be postponed to another day.
As well as the expected narcosis, the air at depth was almost thick enough to feel. As divers we knew a great deal about the theory of breathing compressed gas but being in the chamber really brought home how this differs to being on the surface. Most of us had some idea as to when we noticed narcosis during a dive but none of us was prepared for the totally intoxicated feeling the chamber gave, particularly in such a short time. The added task loading a dive situation could produce could also become a magnifying factor and cold or difficult situations could combine to have this happen at much shallower depths.
After 10 minutes of bottom time we began the journey back to the surface. The DDRC use the Canadian developed DCIEM tables which comprised ascent of around 4m/min and included long stops at 6m and 3m respectively. The balloons showed little sign of change until we reached around 10m, from this time the expansion was very rapid and none of our 'deep' balloons lasted past 5m before bursting. This was a very graphic display of Boyles law in action, the effects were much more noticeable at shallow depths and this is one of the main reasons that DCI is not only restricted to deep dives.
Back at the surface, around 32 minutes after we had started, it was time to join the rest of the group and without giving too much away, they could see by our faces that the experience was to be worth the wait. There was no doubt that it was fun but also as a learning experience it was a valuable lesson for us all. When the two groups were back together again, we reviewed the test answers amid much hilarity as the stupidity of some of our answers became obvious in the cold light of day.
Following this, Matt and Sally gave us a guided tour of the whole facilities. Prior to this visit, most of us had thought of chambers as being exclusively for treating divers with DCI. In fact there are another 12 major clinically accepted conditions that can be treated with hyperbaric oxygen therapy. These range from simple carbon monoxide poisoning to the treatment of cancer, skin grafts and burns. During the year around 70 cases of DCI are treated, against 500 cases of other medical conditions. Some of these will take 6 or more sessions so the work of the chamber really does take place all year round. Sally showed us various graphs showing the positive effects that some of these treatments were having to reduce year on year incedents.
The DDRC is a charity, although funds are raised through the NHS, as a private provider they conduct research into diving, diving physiology and other hyperbaric oxygen treatment. They promote diving safety through training. Our visit was a real eye-opener. The staff were very pleased to be able to demonstrate what they are doing from the most mundane to the very complex operations. They also rely on donations and run a club to promote these and conduct regular organised visits for groups to raise money. They always need volunteers for various research projects and to assist in fund raising activities.
There is no doubt that one day any of us could end up needing their help and assistance. Many divers go into denial thinking that the only people who get DCI hits deserve them for unsafe diving practices. In reality even diving within tables can still lead to a DCI incident. Recognising this can lead to quicker treatment and much better results than ignoring the problem. We also owe it to our own buddies and colleagues to be more responsible and vigilant to recognise the signs earlier in each other. Personally, I hope it does not happen to me but this visit has given me some preparation for what to expect if it does. Staff at the DDRC do not make judgements as to whether anybody 'deserves' a hit, they are there to see that first class attention is given to anyone who comes through their door. A diving doctor is always on hand to answer any questions and recommend action in any incident.
Having experienced their particular brand of hospitality, I would recommend this visit as essential to any serious sport diver to give them a unique insight into the various aspects of hyperbaric medicine. It also gives you a little bit more respect for breathing air at depth and is a great lesson for divers at all levels. One of the good things about this sport is that there is always more to learn - a visit to the DDRC is well worth the long journey to Plymouth.
Find out more information at the DDRC Home Page.
Return to
Main Menu
Copyright © Graham Curran 2001-2002, Changes last made to this page
on: Monday, April 1, 2002 20:12 GMT