About the Paper
The genesis of this chapter stems from my talks on decompression science, which I present at our Memorial Care Long Beach Medical Center semi-annual Introduction to Hyperbaric Medicine and Wound Care Course.
In this chapter, I aim to provide a comprehensive understanding of decompression science by introducing basic concepts and theories related to decompression tables, bubble formation, decompression sickness (DCS) treatment, and the timing of return to diving after experiencing DCS.
Decompression science is a fascinating discipline that offers insights into why one may experience DCS while their diving partner, who followed the same dive profile, remains unaffected. Although there is a wealth of accumulated knowledge on the subject, many questions remain unanswered.
Throughout this chapter, I delve into the theory underlying decompression science. We will explore essential concepts such as ambient pressure, gradients, ongassing, offgassing, tissue saturation, dive table formulation, and perfusion-based tissue compartments.
To make these concepts easily understandable, I present examples in simplified terms using a model compartment with four molecules of inert gas, which can be contrasted with the millions of molecules present in an actual body compartment.
Moreover, I provide practical information on managing decompression sickness and determining when it is safe to resume diving after experiencing an episode of DCS. While some of this information has been mentioned in my book on diving science, "Diving Science... Revisited," it will be further elaborated in this article for a more comprehensive understanding.
To facilitate readability, here are some abbreviations used in the chapter that readers need to take note of:
- AGE = Arterial gas embolism
- ATA = Atmospheres absolute
- DCS = Decompression sickness
- DI = Decompression illness
- DS = Decompression science
- Exempli gratia = Latin meaning for example
- FSW = Feet of seawater
- HB = Hyperbaric
- HBO = Hyperbaric oxygen
- HBORCT = Hyperbaric oxygen recompression treatment
- i.e., = Id est (Latin for that is)
- MSW = Meters of seawater
- OK = Okay
- PFO = Patent foramen ovale
- SCUBA = Self-contained underwater breathing apparatus
The initial appearance of most of the abbreviations are written out, followed by the abbreviation in parentheses. Exceptions include common terminology such as mmHg.
INTRODUCTION
Scope and Goals Decompression science (DS) deals with the phenomena that occur after one decompresses from a higher pressure to a lower-pressure environment. It is not an exacting science, but much is known about what happens in the human body with respect to decompression—almost all of which is a function of the inert gas that comprises the air breathed. It, of course, has applications to divers during their ascents, but also for those who ascend into the atmosphere. The inert gas load is the “price” the diver pays when diving with compressed gas. The “toll” is paid only after the diver ascends.21 However, what the price is and how much the toll amounts to are not always readily apparent. Almost all elements of dive planning focus on preventing DCS. Understanding DS is fundamental to preventing DCS and if it occurs how to manage it. This chapter is written to help understand the “mysterious physiological jungle” of DS. The first section defines terms fundamental to DS. Next, simplistic models of on-gassing and off-gassing are described. This leads to the concepts of tissue half-times and the construction of decompression tables with their practical applications to dive profiles and dive computers. Finally, the chapter concludes with why DCS occurs, what its clinical presentations are, the treatment for it when to return to diving after an episode, and how to minimize the possibility that it occurs.
