ABSTRACT

Decompression algorithms gain efficacy by their ability to track diving data, often independent of physical interpretation. In that sense, the bottom line for computational models is utility, operational reliability, and reproducibility. Correct models can achieve such ends, but almost any model with sufficient parameter latitude might achieve those same ends. It is fair to say that decompression models admit varying degrees of computational license, that model parameters may not correlate as complete set with the real world, and that not all mechanisms are addressed optimally.

That is, perhaps, one reason why we see representative diving sectors, such as sport, military, commercial, and research, employing different tables, computers, models, and algorithms. Yet, given this situation, dual phase (dissolved gas plus bubbles) models attempting to treat both free and dissolved gas decompression, bubbles and gas nuclei, and free phase trigger points appear preferable. Phase models have the right physical signatures, and thus the potential to extrapolate reasonably when confronting new applications and data. That is said after logging 10 -15 yrs correlating data with decompression algorithms from all sectors of the diving world and for purposes of profile analysis and safe decompression staging. Coarse grained as models are, modern dual phase models seem to work best with a safe diving record to date.

A discussion of decompression models in technical diving is presented, underscoring dual phase dynamics and quantifying metrics in tissue and blood. All can be grouped into three super classes for simplicity, namely, dissolved gas, pseudo-bubble, and bubble models. Specific models are popularly deemed the multitissue, diffusion, split phase gradient, linear-exponential, asymmetric tissue, thermodynamic, varying permeability, reduced gradient bubble, modified gradient phase, tissue bubble diffusion, and linear-exponential phase models.

Underlying concepts are listed, and diver staging regimens are underscored. Implementations, diving sectors, and correlations are indicated for models with a history of widespread acceptance, utilization, and safe application across recreational, scientific, military, research, and technical communities. Presently, all models are incomplete, but many are useful, having resulted in diving tables, underwater meters, and dive planning software. Those herein employ varying degrees of calibration and data tuning and are discussed appropriately.
We also discuss bubble metrics in tissue and blood as a backdrop against decompression models.

The past fifteen years, or so, have witnessed changes and additions to diving protocols and table procedures, such as shorter nonstop time limits, slower ascent rates, shallow safety stops, ascending repetitive profiles, deep stop decompression, helium based breathing mixtures, permissible reverse profiles, multilevel techniques, both faster and slower controlling repetitive tissue halftimes, smaller critical tensions, longer flying-after-diving surface intervals, and others. Stimulated by Doppler and imaging technology, table and decompression meter development, theory, statistics, chamber and animal testing, or safer diving consensus, these modifications affect a gamut of activity, spanning bounce to decompression, single to multiday, and air to mixed gas diving. As it turns out, there is growing support for many protocols on operational, experimental, and theoretical grounds, with bubble dynamics addressing many concerns on plausible bases, but with further testing or profile data analyses requisite. Here, obviously, profile Data Banks play major roles.