DECOMPRESSION AND THE DEEP STOP WORKSHOP OVERVIEW

Theoretical and practical solutions as to how to ascend or decompress after diving have been considered since Haldane some 100 years ago, yet decompression sickness (DCS) still occurs. The traditional “Haldanian” approach to planning decompression has been to limit supersaturation (the difference between tissue inert gas tension and ambient pressure) according to empirically derived rules that purportedly maximize gradients for inert gas washout and therefore provide a low risk of DCS.  The use of Doppler to monitor the central venous circulation, however, shows this approach still frequently results in bubble formation.  Other more recent decompression theories have relied on so called “bubble models” which focus on prevention of such bubble formation.  To do this, the algorithms limit supersaturation more aggressively and typically result in the imposition of deeper decompression stops.  These have been used quite successfully for many years by technical divers for deep diving.   In recent years, the utilization of a deep stop by recreational scuba divers at depths less than 130 fsw (41 m) also has been proposed.  This is now appearing in dive computers using “bubble models” such as Varying Permeability or the Reduced Gradient Bubble Model or the Half the Depth Model. Some training agencies have also incorporated deep stops into their training regimens.  However, there is debate as to when to stop, for how long and how often in regard to whether such a deep stop does limit bubble growth or ameliorate the risk of DCS.  This workshop has brought together the most active international individuals with practical human data, animal research and theoretical concepts to help clarify the role of “deep stops” in contemporary recreational scuba and technical diving, and to point out what we know as well as indicate future research needs.