SPECIAL May 1998

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The Buddy Inspiration rebreather

Now he's a believer

John Bantin tried out AP Valves' Buddy Inspiration in prototype form back in 1996, and was excited by the possibilities it seemed to offer. Hard work still had to be done to prepare this fully closed-circuit rebreather for the market; some said it would never make it. But it did, and a week in the Maldives has given our tester the proof he needed - find out how he took the wonder gear beyond 50m during a two-hour dive, and brought back a picture (below) as evidence.

I looked at my Aladin Nitrox. It showed 99 minutes of ascent-time needed, with the first stop a lengthy one at 12m. It was then that I realised that 99 minutes was the maximum shown on the Aladin display - and I was going to need a lot more than that.
Was I worried? Hardly. I made my way up to where I met the reef at 40m, preparing to make my first stop at 33m and intending to omit the lengthy 3m stop that the Aladin (set for nitrox 21) would require.
Was I attempting suicide? I'm sorry to disappoint my critics, but I was not!
My buddy and I had been cruising out in the deep blue at around 45m, the tiny figures of Axel and Peter hovering above us bedecked with multiple tanks at around 30m. Suddenly Axel became animated. He was pointing down past us.
A group of hammerhead sharks was passing slowly by, golden bodies shimmering through the thermocline, lit by the first rays of the morning sun over the Maldives.
Without hesitation I dropped towards them. My buddy did the same. Passing into the unexpected chill of water a few degrees cooler than the 28C above, we enjoyed the clarity of vision denied the others as these magnificent creatures cruised by.
Many divers have been to Hammerhead Point at Madivaru and waited in vain for such a sighting. We had waited at depth for a long time for this success.
What I did not know was that my buddy had tried to get ahead of the sharks to give me that rare photo-opportunity of a diver swimming alongside them. Not realising this, I turned to where I had expected him to be and in that way we became separated. I was at 53m and had been at great depth for 36 minutes.
A series of dive profiles was set out on my slate, but none of them now applied. The longest, deepest plan of 25 minutes at 55m meant that the longest stop (at 6m) would have re-quired 26 minutes. I had long passed needing as little as this.
Pausing for two minutes at 21m and again at 15m, I made the lengthy stop demanded by the Aladin's air algorithm at 12m and 9m, then moved up to 6m.
The computer now displayed 29 minutes at 6m, with a total ascent time of 85 minutes. I hovered next to the reef and extrapolated the original dive plan. If I stayed at 6m I could dispense with the 55-minute stop at 3m.
Now these figures probably sound crazy to any experienced scuba diver, and would have sounded crazy to me a week earlier. But I was no longer an ordinary scuba diver. I was breathing the high oxygen percentages afforded by the Buddy Inspiration closed-circuit rebreather.
I had come to the island of Ellaidhoo in the Maldives to test the revolutionary unit, accompanied by Martin Parker, Managing Director of AP Valves, which makes the Inspiration.
On cue the dive boat found me, revealed by the big yellow box on my back. Martin, already back aboard, lowered his Aladin to me on a rope. It read: "SOS". He had bent it and I was about to do the same to mine!
After a hearty breakfast we made a second dive. Axel and Peter, using open-circuit scuba, loaded on more nitrogen. We stayed at 12m and spent another 45 minutes breathing oxygen at a partial pressure of 1.3 bar.
At this depth we were breathing it at 59 per cent. The dive was effectively therapeutic recompression.

Setting up
Rigging a rebreather can look daunting when you are dripping with sweat in the tropical heat and would prefer simply to sling a tank on your back and get in the water. .
I used two 3-litre cylinders, one with air at 200 bar to be used as a diluent and for buoyancy control, the other with oxygen - normally about 100 bar, because it was decanted from larger, partly used cylinders.
After checking that the scrubber material, Sofnolime or Draegersorb, was in good condition, you close the unit and mount it on your back like any other scuba unit, except that the twin-hose assembly with its mouthpiece goes over your hea.
The total weight of about 30kg sounds a lot, but felt much the same as a 12-litre cylinder with an open-circuit rig once the BC's integrated-weight system was loaded.
On my first dive I went in weighted for my 7mm suit and the 12-litre aluminium tank I had worn a few weeks earlier. This required me to put lots of air in the Inspiration's Redwing BC, bending myself almost double when I tried to swim horizontally.
After that I dispensed with 6kg of lead and suffered no further discomfort or backache.
Next job is to turn on the two computers controlling the oxygen levels, the second of which is a back-up slave. After a self-diagnostic check for battery level and the like, and two piercing test-screams from the warning bleeper, the master computer asks: "Dive Now?" Pushing a central switch tells it yes.
Serious questions follow: "Have you opened the O2 gas valve?"; "Is the mouthpiece open?"; and so on. These must be answered in the same way.
By following the check-list on the master computer screen it seems impossible to make a mistake - unless you switch it all off after the check and later hit the water merrily breathing a loop of gas with a rapidly reducing oxygen level.
I can only assume that people who do this are either trying to save the life of the computer's battery (nominally 35 hours each for both master and slave) or to dramatically shorten their own.
Curiously there is no reminder to open the valve on the diluent cylinder. Martin assures me that this omission will soon be rectified.
The unit provides two alternative set-points for ppO2. The default settings of 0.7 and 1.3 bar can be altered by the user at any time, even during the dive, by going into "menu mode".
The set-point is displayed alongside the read-outs from the three oxygen sensor cells. The computer chooses the two that agree most closely. As it would be impossible to attain a ppO2 of 1.3 at the surface, where ambient pressure is only one bar, the lower set-point is used initially. After descending beyond 3m you switch to the higher set-point of 1.3 bar, and the process is reversed on the way back up.
To choose the setting, you push for more than two seconds the central sliding control switch on the chosen master unit, set diagonally to the others to avoid mistakes in poor visibility.
The two outer switches are merely up and down controls for changing settings in menu mode, which is entered by pushing both of them simultaneously.

Under water
USING the Inspiration is less tricky than might at first appear. I had not used a rebreather since trying out its pre-production prototype with inventor Dave Thompson nearly 18 months before. Yet the first time out I managed to dive to a maximum depth of 34m for 90 minutes with no difficulty other than that weight problem.
On a dive I would float at the surface before exhaling through my nose, thereby losing all gas from my lungs - the ones I was born with and the Inspiration's counter-lung. I then dropped quickly.
To inhale, I had to top up with air from the diluent cylinder by pressing a button rather like the direct-feed to a drysuit. This is when you find out if you have forgotten to open the diluent gas valve. Luckily both this and the O2 valve fall easily to hand!
As I descended I found I needed to add extra volume constantly to my lungs and counter-lung, but avoided filling them too full, as this would make buoyancy control more difficult. I used the wing-style BC for additional buoyancy control once past the 10m mark.
I needed to put diluent into both counter-lung and BC only during descents, but it was essential for gas to be retained in the breathing loop.
If you need to clear your mask or breathe out through the nose at any time except during an ascent, you need to top up the lost volume with more diluent. It is important that your mask has no tiny leaks in the skirt.
During the dive the gas is breathed from the loop and the resulting carbon dioxide removed by the scrubber unit.
As the level of oxygen drops because it has been metabolised, the three O2 sensors feed information to the master computer, which opens a solenoid valve and adds oxygen as required to give the most appropriate nitrox mix at any given depth. The computer display can be seen changing from moment to moment as the level of oxygen in the system changes, proving that the system is working. A built-in timer records scrubber life.
With a bit of practice I found that I was using about 25 bar of both diluent and O2 during a typical dive of 90 to 120 minutes.
On ascent expanding air has to be released from both BC and counter-lung. I found it best to deal with the BC first, unless the counter-lung became so full it caused discomfort.
There is a dramatic drop in ppO2 at this time, so the computer constantly asks the solenoid-operated O2 valve for more gas.
To avoid "hamster cheeks" and release air from the lungs, I had to blow out through the nose, but if things got out of hand I found that the pull-cord on a fast dump-valve to the inhalation bag was instantly effective.
Letting go of the mouthpiece without shutting it first could cause a dramatic loss of gas from the breathing loop and allow water into the unit.
However, I am pleased to say that the mouthpiece could be opened and closed far more easily than on any other rebreather I have used. Two movable weights are positioned along the hoses to stop them floating upwards.

Precautions
A loud buzzer warns of abnormally low or high oxygen levels. Drills learned on the training course include coping with a flooded mouthpiece and operating the unit manually should the O2 solenoid valve stick open or closed. There is an O2 direct-feed to the counter-lung for this purpose.
The scrubber unit is designed to cope with the intrusion of quite a lot of water. On one occasion I heard gurgling noises after about 90 minutes of diving, but a flood is not disastrous unless the diver insists on doing somersaults immediately afterwards.
The instruction manual repeatedly exhorts the user: "If in doubt - bail out!" The BC allows you to do this by way of a Buddy Auto-Air breathing valve, which gives access to the breathing gas (air) in the diluent cylinder.
For the 50m-plus dive I took the precaution of adding another 7-litre sling-tank of nitrox 36 to the rig, but by this time, 12 dives and at least 18 hours of Inspiration rebreather diving into the trip, I was confident that I would not need it.
I also had the option of adding an O2-clean additional second stage to the first stage of the main oxygen supply valve, to use as a pure oxygen decompression bail-out gas at less than 6m.

Maintenance
the Buddy Inspiration seems robustly made throughout, with all the components screwing together in a precise and satisfying manner.
Manufacturing quality is high and this was reflected in the long gestation period between the first pre-production prototypes and the production model being available. AP Valves has obviously invested a lot in expensive injection moulds.
The scrubber unit is a sophisticated piece of engineering rather than the simple plastic box seen with other rebreathers. It has two water-resistant membranes and an inner cartridge that can be pre-loaded when it is most convenient.
This dispenses with the need to mess about with loose powder when out in a boat.
After each dive I found quite a lot of condensation in the scrubber unit, squeezed out when the exhaled gas was passed through the chemical. It was easily disposed of, and I took the precaution between dives of blowing droplets of condensation away from the sensor cells with a jet of compressed air from the direct-feed hose of the diluent cylinder.
Twice during the week's diving it was thought prudent to flush out the counter-lung with disinfectant, and I kept the mouthpiece shut to prevent any tropical beasties discovering a new place to hide during the night.

Is it all worth it?
THERE is no point using a closed-circuit rebreather to do the same dive profiles that you now do using open-circuit scuba, or even semi-closed circuit rebreathers.
These, the Draeger Dolphin or Atlantis 1 use a pre-mix of nitrox more efficiently than ordinary open circuit scuba to extend dive times to a degree, but are subject to the same decompression obligations.
When it comes to sneaking up on underwater wildlife, the Buddy Inspiration does not offer some magic cloak of invisibility.
I was still a large and somewhat cumbersome animal. But with a no-stop time at 20m of almost three hours - including other limitations such as scrubber life and oxygen toxicity limits - you have time on your hands. Other animals can grow accustomed to your presence.
Neither are there any sudden, noisy ejaculations of bubbles to shatter their confidence. The only time you need to vent off small amounts of breathing gas is on the way up.
I found my dive durations were limited only by the duration of my bladder. That is, until I got used to breaking a rule of a life-time!
By hiding inside the upturned wreck of a small steel supply boat at 34m I was able to enjoy close encounters with all manner of creatures that passed by.
I would watch open-circuit scuba divers come down and circle the wreck, sometimes returning on their second dives!
While I was concealed by a large shoal of grunts one day some divers spotted my spare camera lying on the seabed. The exhilaration of the finder as he clipped its lanyard to his BC turned to confusion as I seemed to appear from nowhere and took it back.
"Thank you, but that's my camera!" I said politely. Because that is the other thing about the Inspiration - it allows you to speak into the mouthpiece cavity and be understood!
When all my film was finished, it amused me to go up to open-circuit divers, ask them complex questions and enjoy their frustration at being unable to communicate other than with inadequate gesticulations. I'm afraid I can be a bit sadistic.
At around £3000 the Buddy Inspiration represents a considerable extra expense to a diver who probably already owns a full set of open-circuit equipment.
That said, the cost includes the equivalent of two regulators, two tanks and a BC - in tekkie terms that could easily add up to £2000.
The additional time under water is also reflected in both the amount of care and preparation needed, and the cost of oxygen supplies and CO2 absorbent.
A fill of Sofnolime costs £9.50 and lasts for more than six hours of diving. A 3-litre cylinder of O2 filled to 200 bar costs about £5 and should also be good enough for at least six hours.
My conclusion? The Buddy Inspiration could be the most significant development in scuba diving since Cousteau first popularised the aqualung.

AP Valves 01326 561040

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Advantages of a constant ppO2 The advantages of nitrox are well-known. By increasing the level of oxygen in the gas we breathe, the nitrogen in the mix is reduced, so we absorb less of it under water. This means longer no-stop or shorter deco-stop times. However, with any particular nitrox mix there is a maximum operating depth (MOD) caused by the toxic effects of oxygen under pressure. It is generally thought that a partial pressure of oxygen (ppO2) in excess of 1.6 bar can cause harmful effects to the nervous system that can lead to epileptic-like fits and, under water, to death by drowning. Most nitrox training agencies suggest an MOD based on a ppO2 of 1.4 bar. The Buddy Inspiration rebreather makes nitrox by mixing air (O2 and N2) with pure O2. Sensors constantly monitor the O2 levels being breathed and keep the ppO2 constant at (normally) 1.3 bar by adding O2. Oxygen is added to the breathing gas when the level is reduced by metabolism or by ascending to a shallower depth. By choosing a set point of 1.3 bar, minor fluctuations can be accepted without breaching 1.4 bar. Some divers will inevitably choose a higher setting. The mixes delivered at depth are as follows: at 50m 21.6 per cent O2 (near air) at 40m 26 per cent O2 at 30m 32.5per cent O2 at 20m 43 per cent O2 at 15m 52 per cent O2 at 12m 59 per cent O2 at 9m 68 per cent O2 at 6m 81 per cent O2. At any given moment the breathing mix available from the fully closed-circuit Buddy Inspiration has the least nitrogen possible, resulting in the shortest decompression requirements while never allowing the ppO2 to reach a dangerous level. The effect is to allow the diver to decompress during an ascent on a progressively stronger mix of nitrox. The Inspiration rebreather can also be safely used deeper than 52m, but with a diluent other than ordinary air, such as heliox. Trimix divers can carry a separate cylinder of bottom gas which they can plug into the diluent feed valve when they need it.

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Where we did the test Ellaidhoo is a tiny island in Ari Atoll, about 50 miles from Male, the capital island of the Maldives, in the Indian Ocean. It is reached by Twin-Otter float-plane or boat. Ellaidhoo, with enough space for about 50 simple bungalows for a total of 100 guests, restaurant, bar and tourist shop, is a diver's island. You can walk around it in less than 15 minutes but it has a deep-water reef immediately at its shore giving easy access and the possibility of diving as much as your body can stand! Dive-boat trips are scheduled twice a day, but you are free to shore dive whenever you want. The dive centre can provide nitrox 32 and 36 from de-nitrogenised air, as well as pure O2 for other uses. We had made special arrangements with Emirates Airlines to ship out the four weighty 3-litre cylinders, not knowing that the centre could have provided identical O2-clean cylinders from stock. Ellaidhoo already offers semi-closed rebreather facilities and training with the Draeger Atlantis and now has one of the first dive centres to be equipped with the closed-circuit Buddy Inspiration. One imagines that in future Inspiration-equipped dive centres will be more common worldide, and travelling divers will not have the hassle of taking the heavy components on the plane. UK agent: Maldives Scuba Tours. 01449 780220.

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Appeared in DIVER - May 1998

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