O the Use of a Gas-Cavitation Model to Generate Prototypal Air and Helium Decompression Schedules for Divers

During the last several years, significant progress has been made in elucidating the bubble-nucleation phenomenon in aqueous media. According to the varying-permeability model, cavitation nuclei consist of spherical gas phases that are small enough to remain in solution, yet strong enough to resist collapse, their stability being provided by elastic skins or membranes consisting of surface-active molecules. By tracking the radial size of bubble nuclei during changes in ambient pressure, the model has provided precise quantitative descriptions of bubble-counting experiments in gelatin. It has also been used to trace levels of incidence for decompression sickness in several animal species, including fingerling salmon, rats, and humans. More recently, bubble nuclei have been observed directly in distilled water, gelatin, and blood using a variety of microscopic techniques. This work details the application of the varying -permeability model to the problem of decompression sickness through the construction of a prototypal set of decompression schedules. These schedules were generated by a short computer program based on the model equations. Once initialized with a group of tissue half-times and four free parameters selected to optimize decompression safety and speed, the program was used to calculate air diving tables for depths ranging from 30-300 fsw, requiring only the corresponding depth excursions and bottom times as input. Following the reevaluation and readjustment of the program and the model parameters, a similar set of decompression schedules for helium dives was produced.