Tag Archives: Decompression

Getting Decompression Sickness

Dive 4 PADI Deep Diver Course
Dive 4 PADI Deep Diver Course Max Depth 104ft

Here it is almost a week later, and I am still shaking my head.  Sunday morning, I was running dive three of the PADI Deep Diver Specialty course, and as always very much looking forward to the next set of dives.  Deep is what I do, what I love, but things will not be so routine over the next couple of hours.

As we were headed out to the decent point, I was reviewing the procedures for the dive with my two students. What the rock bottom pressure was, when we had to be off the bottom, where our first deep stops would begin, so on and so on.  The decent was picture perfect, checks at 10, more checks at 20, and then the last set of checks at 30 as we decided the dive was a go.  The depths were ticking off on my computer, 80, 90, 100 I could see the beautiful cloud sponges come into view, one at first then more and more and bigger and bigger, 115, 120, 130 we reach the target depth by minute 3.  Beautiful, dark breath taking is the best way to describe it.  The only sound I can here is my breathing.  The wall to my right is gorgeous teaming with life.

We continued on with the dive and at approximately minute 9  one of the students signals me, he is approaching rock bottom so I slowly begin the ascent back to the surface, reluctant but ascending never the less.  We reach 80 feet an begin our deep stops, 30 second holds every 10 feet until we reach the safety stop area and for todays dive the 20 foot mark is our agreed upon deep stop depth.  Once there we execute a min 8 minute simulated emergency decompression stop, where we hang at that depth for 8 minutes and then slowly ascend to the surface from there. The dive was picture perfect, text book if you will.

After a 1 hour 18 minute surface interval we descend down on the graduation dive of the PADI Deep Diver course, and do a total repeat of the the first dive though the maximum depth has been shallowed to 130 feet, and once again things were picture perfect.  Some 35 minutes later we are on the surface rinsing our gear, chatting and reviewing everything that had happened, as we loaded the gear and departed.  Routine it was, the same thing I do time and time again, though the day would not end as routinely as it had begun.

Comex 30 Re-Compression Chamber Dive
Comex 30

We departed Whytecliff Park in West Vancouver, and headed back to the dive centre.  Just as I had exited the highway, I had a severe case of virtigo happen and I could barely keep the vehicle on the road, so I pulled off, and had Greg V drive so we could make it back to the shop. The symptoms seemed to pass within 5 – 6 minutes and life got back to normal for a few minutes, until the severe abdominal pain started with skin itchiness, shoulder pain and numbness radiating over the left side on my back to the shoulder and into the jaw.  I knew then something was not right, so I went on oxygen and called the Vancouver General Hospital Hyperbaric  Chamber where I was told to report to emergency right away.

Once I arrived at VGH, I was ushered in through the Emergency Department, Xrayed, CT Scanned, IV’d O2’d and into the chamber where I did an 8 hour long Comex 30 Re-compression profile.  Things are doing much better, though it appears I will be out of the water for 6 weeks,  I think that is the longest I have been out of the water in the past 6 years, but a little R&R never killed anyone…maybe some travel is in order?  Mmmmm could be fun!

Deep Stop RGBM Algorithm

Classical Haldane

Classical Haldane-type decompression calculation assumes that all gas is dissolved into the tissues, and remains dissolved as long as the maximum tissue tensions are not exceeded.  Bubbles are assumed to form only when the ascent rate or the m-values are exceeded.  As the pressure gradient is invertedly proportional to the surrounding pressure, the diver is brought as shallow as possible, as fast as possible, in order to maximize offgasing.

Doppler-studies show, that microbubbles are present on all doves.  Therefore the effects of free gas need also to be considered in decompression calculations

Suunto RGBM

The Suunto RGBM was designed to protect the recreational diver from the effects of micro-bubble build up.  It incorporates a bubble-factor based tracking system to adapt the decompression requirement based on conduct dive profiles.  The maximum ascent provides maximum offgassing and a clean decompression curve.  A 3min recommended safety stop is added to deal with adverse ascent rate violation.  An extended surface interval is promoted when microbubbling is present.



Suunto Deep Stop RGBM

The Suunto Deep Stop RGBM algorithm increases microbubble suppression on deep dives even further by introducing iterative deep stops.

The first deep stop is placed at half the pressure difference between your maximum depth and the ceiling depth.  Once the deep stop depth is attained, the next deep stop will again be introduced half-way to the ceiling, and so on.  Once the ceiling depth is reached, continous decompression is employed for staging the end of the profile.

In the Suunto D9 and Suunto Vytec DS the user can choose between the familiar Safety Stop providing Suunto RGBM, or the new Deep Stop RGBM.