While back in the UK I had the opportunity to complete a 'Dry Dive' in the Hyperbaric Decompression Chamber of Midlands Diving Chamber, based in Rugby.
Although not a breath hold dive (to reach 50m and return without safety stops would take 10 minutes, close to the static world record time!), this was a fascinating insight of how the theory and technology combines to provide recompression therapy to divers and non divers alike.
Interesting aspects during the dive include the temperature change. Inside it reached 33c+, especially higher in the chamber, so while you are sweating from your head your feet are feeling cold! Equalization was different to in the water and had to be carried out much more frequently during the chamber dive. In the first 3m we must have already equalized in excess of 10 times! Medical scrubs are worn to prevent any accidents from static electricity in what was a high oxygen environment and seemed prudent after a recent accident in China.
Nitrogen narcosis is of course evident and at depth we tried to complete some spelling challenges which took longer and were infinitely more funny than would be the case at the surface! The pressure changes evident at depth were highlighted using pieces of neoprene, inflatable balls, balloons and exploding table tennis balls and not forgetting the ridiculously high pitched voices caused by pressure on the vocal chords :-)
100% oxygen was breathed at safety stops as part of the ascent and meant we actually came out of the chamber with less Nitrogen in the body than we went in with.
The dive was following a US Navy schedule; (170FSW) 52.1m/25min:
1928 Left surface
1929 arrived 3m first stop
1929 left 3m
1935 arrived 50m all well
1942 left 50m
1946 arrived 12m, 1min deco Air
1947 left 12m
1947 arrived 9m
1947 on 100%02 @1.9 pp02 max
1951 depart 9m
1952 arrive 6m @1.6 pp02 max
2015 depart 6m
2015 off 02
2016 on surface.
Total deco time @ 29min with 28mins on 100% 02
Total dive time 48mins.
With thanks to Ian and Tracey Watson and the staff at Midlands Diving Chamber