Abstract

The question of bubble regeneration and broadening (Ostwald ripening) in the diver under compression-decompression is virtually unanswered and untractable. Effects in vivo have not been measured nor quantified to date and remain unlikely soon. We take up this question and suggest hypothetical impacts on diver staging using available data and recent experimental results in the laboratory. Four well known and widely used diver staging models, USN, ZHL, VPM and RGBM, provide a framework to estimate hypothetical effects in mixed gas diving on open circuit (OC) and rebreather (RB) systems. These are estimates and are neither verified nor tested in divers. However, the projections are conservative, increasing decompression time and shortening no decompression time limits (NDL), so that their implementation in diver staging protocols, software, dive computers and dive tables is patently safe and of interest to modelers, table designers, training agencies, dive tenders, engineers, doctors, dive computer vendors and related professionals. Experiments impacting broadening and regeneration are briefly detailed. Are the regeneration and broadening studies in gel, blood, agar, water and fluorocarbon substrates. Features of diving models (USN, ZHL, VPM, RGBM) affected by bubble regeneration and broadening are quantified within model frameworks. Comparative results are given with and without regeneration and broadening. Regeneration and broadening times can range from hours to days. Corresponding decreases in NDLs and increases in decompression times range 2% to 8% for nominal (recreational) exposures and 10% to 16% for extreme diving and extended (technical) exposures. Overall effects are thus small to moderate, but diver staging effects will increase with decreasing regeneration time scales and increase with increasing broadening time scales for given depth, breathing mixture and bottom time. Effects will always increase with depth. Regeneration effects and broadening effects for time scales beyond 8hrs are relatively small overall in this hypothetical study within the USN ZHL, VPM and RGBM frameworks. Hopefully real experiments measuring bubble regeneration and broadening in the body will pin these issues down in the future. This analysis represents a first time ever codification of hypothetical effects of bubble regeneration and broadening on diver decompression staging..

Keywords: Bubble regeneration; Bubble broadening; DCS risk; Decompression models; Staging procedures