INERT GAS NARCOSIS - JB Morrison 2006 

Over the past two centuries, various observations have been made relating hyperbaric environments of air to symptoms of narcosis and intoxication. Compressed air narcosis was noted as early as 1835 by Junod, a Frenchman who was also involved in the development of pumps and hard hat diving suits. He noted that “imagination became lively and brain function was activated”. He suggested that the symptoms observed were similar to “intoxication”. In 1861, Green reported feelings of sleepiness, hallucinations and impaired judgement.

These early observations were very general and not very scientific. Among reports made in the nineteenth century, Paul Bert (1878) suggested that the symptoms could be due to the increased pressure of the inspired air. Bert studied both altitude and pressure physiology and his extensive work "La Pression barometrique" laid the foundations of Environmental Physiology.

Clearing Up The Confusion About Deep Stops By Erik C. Baker,  The author is an electrical engineer with an architecture/engineering firm in Pennsylvania who has developed several computer programs to improve the safety of his cave and trimix diving.

The old adage, "an ounce of prevention is worth a pound of cure", is certainly applicable to the various symptoms of decompression sickness (DCS). The best treatment of all for these maladies is to complete a sufficient decompression profile in the first place. Technical divers have observed that many ailments can be avoided by including deep stops in their profiles. A closer examination of the decompression model reveals that this practice serves to reduce or eliminate excessive overpressure gradients. Knowing this, the model can be modified to provide precise control of gradients and stops can be calculated within the decompression zone to the depth of the "deepest possible decompression stop."

Gas Exchange, Partial Pressure Gradients and the Oxygen Window
Johnny E. Brian, Jr., M.D.

The oxygen window. Inherent unsaturation. Partial pressure vacancy. Most divers with an interest in decompression diving have likely encountered one of these terms at some time. All three terms are used to describe the same physical phenomenon. For this article, the term oxygen window will be used, as it appears to be the most commonly applied term. However, the terms inherent unsaturation and partial pressure vacancy more correctly describe the physical phenomenon. Current techniques of oxygen-facilitated decompression diving are based on use of the oxygen window.

Despite common use by divers of the oxygen window, it appears to be one of the least appreciated concepts in decompression diving. Understanding the oxygen window requires knowledge of circulatory and gas transport physiology, and the best place to start is with normobaric physiology.

The Importance of Deep Safety Stops: Rethinking Ascent Patterns From Decompression Dives by Richard L. Pyle

Before I begin, let's make something perfectly clear: I am a fish-nerd (i.e., anichthyologist). For the purposes of this commentary, that means two things. First, it means that I have spent a lot of time underwater. Second, although I am I biologist and understand quite a bit about animal physiology, I am not an expert in decompression physiology. Keep these two things in mind when you read what I have to say.

Back before the concept of "technical diving" existed, I used to do more dives to depths of 180-220 feet than I care to remember. Because of the tremendous sample size of dives, I eventually began to notice a few patterns. Quite frequently after these dives, I would feel some level of fatigue or malaise. It was clear that these post-dive symptoms had more to do with inert-gas loading than with physical exertion or thermal exposure, because the symptoms would generally be much more severe after spending less than an hour in the water for a 200-foot dive than they would after spending 4 to 6 hours at much shallower depths.

Extract: We are who we think we are, and we can do what we think we can do, if we maintain a positive self-image. Self-image is really concerned with self-perception and self-communication. At times, we can talk ourselves into having a bad day, convincing ourselves that we are powerless to change the outcome. Few can talk themselves into a good day. Our perception of ourselves is the basis for self-talk, which in turn, influences performance, which creates self-image, more self-talk, more imaging, and so on back and forth. When we blow a neutral buoyancy control exercise, we can often talk ourselves into the same rut next time. Negative self-image feeds on failures.

HEAD GAMES OF DIVING;  B.R. Wienke

As divers, we often view our performance in terms of the manueuvers we can or cannot do. Skills, and their respective levels of development, are certainly of concern to both the beginning and accomplished diver. In grooving motor skills and attempting to enhance our performance, it appears useful to consider a number of competing factors impacting physical performance and mental perception, and especially their interplay, the so called head games of competitive endeavor.

Online with the RGBM: A Modern Phase Algorithm and Diveware Implementation

By Bruce Wienke
Senior Project Leader in the Nuclear Technology/ Simulation And Computing Office at the Los Alamos National Laboratory

Both Suunto and Abysmal Diving have released products incorporating a modern phase algorithm, called the Reduced Gradient Bubble Model (RGBM), for diving. An iterative approach to staging diver ascents, the RGBM employs separated phase volumes as limit points, instead of the usual Haldane (maximum) critical tensions across tissue compartments. The model is inclusive (altitude, repetitive, mixed gas, decompression, saturation, nonstop exposures), treating both dissolved and free gas phase buildup and elimination. NAUI Technical Diving employed the RGBM to schedule nonstop and decompression training protocols on trimix, heliox, and nitrox while also testing gas switching alternatives for deep exposures.