Saturation decompression is a physiological process of transition from one steady state, full saturation with inert gas at pressure, to another one: standard conditions at surface. It is defined by the borderline condition for time spent at a particular depth (pressure) and inert gas in the breathing mixture (nitrogen, helium). It is a delicate and long lasting process during which single milliliters of inert gas are eliminated every minute, and any disturbance can lead to the creation of gas bubbles leading to decompression sickness (DCS). Most operational procedures rely on experimentally found parameters describing a continuous slow decompression rate. In Poland, the system for programming of continuous decompression after saturation with compressed air and nitrox has been developed as based on the concept of the Extended Oxygen Window (EOW). EOW mainly depends on the physiology of the metabolic oxygen window—also called inherent unsaturation or partial pressure vacancy—but also on metabolism of carbon dioxide, the existence of water vapor, as well as tissue tension. Initially, ambient pressure can be reduced at a higher rate allowing the elimination of inert gas from faster compartments using the EOW concept, and maximum outflow of nitrogen. Then, keeping a driving force for long decompression not exceeding the EOW allows optimal elimination of nitrogen from the limiting compartment with half-time of 360 min. The model has been theoretically verified through its application for estimation of risk of decompression sickness in published systems of air and nitrox saturation decompressions, where DCS cases were observed. Clear dose-reaction relation exists, and this confirms that any supersaturation over the EOW creates a risk for DCS. Using the concept of the EOW, 76 man-decompressions were conducted after air and nitrox saturations in depth range between 18 and 45 meters with no single case of DCS. In summary, the EOW concept describes physiology of decompression after saturation with nitrogen-based breathing mixtures.
Hyperbaric oxygen toxicity studies were conducted on rabbits using the opsonic index determination.The study was conducted on 15 animals that had opsonin index examined prior to hyperbaric oxygen exposure. They were then subjected to an hourly exposure to hyperbaric oxygen with overpressure values of 1.8, 2.4 and 3.1 atm in groups of 5 animals. After the exposure, the opsonium index was re-examined upon the lapse of 1, 2 and 10 days. Parallelly, the morphological image of the blood was examined.There was a statistically significant increase in the index in the first two days after exposure, independent of the value of oxygen overpressure. On the 10th day, the index value approached the initial one.
The aim of this work is to determine the dynamics of nitrogen saturation in small laboratory animals. Nitrogen was chosen as a model gas in this study because of its availability and characteristics, as it is not metabolised and is subject to passive diffusion. By subjecting different species of animals to hyperbaric exposures of increasing time and pressure, the study aimed to identify how rapid a decompression was possible to achieve an outcome that saw 50% of the animals surviving the ensuing acute decompression sickness.
The basic parameters of hyperbaric exposure - pressure and time - made it possible to describe the saturation phenomena on the basis of partial saturation periods and to show whether a small animal organism can be considered as a single compartment model.
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