Introduction Consecutive CCR diving frequently exposes the human body to both hyperbaric and hyperoxic environments. The NOAA guidelines have been developed as safety limits for oxygen exposure. However, there have been reports of lung abnormalities and myopic shifts in the literature. The aim of this study was to analyze the effects of a 31-day period of repeated deep and long CCR dives on divers’ lung function and visual acuity.

Introduction As we have been studying oxygen for 250 years [1], we may think that we know it all. Admittedly, we have learned a considerable amount since the first use of the term “phlogiston”, a word coined by Jonass Johann Joachim Becher in the 17th century to refer to what we now call oxygen. Phlogiston is the neutral form of “phlogistos”, meaning “inflammable”. The word comes from “phlogizein”, meaning “put on fire, burning”, and from “phlox” (in the genitive form “phlogos”), meaning “flame”; it was the hypothetical theory of fire and was a constituent of all combustible material.

Background: Recreational diving creates risk for decompression sickness (DCS), which can occur in SCUBA diving even if current decompression algorithms are respected. The aim of this study was to identify the primary risk factors for decompression sickness in real-world regular recreational diving.

Introduction: The popularity of SCUBA diving is steadily increasing together with the number of dives and correlateci decompression sickness (DCS) cases per year. DAN Europe continues to collect in-field data from divers building the largest database of dive parameters, post-dive gas bubble load, persona I risk factors and occurrence of DCS. An initially developed database (DAN DB) including specific questionnaires for data collection allowed in 2017 the statistica I analysis of 39,099 electronically record ed open circuit dives made by 2,629 European divers (2,189 mal es 83.3%, 440 females 16. 7%) over 5 years [1]. This report includes the update of the database. Methods: An originally developed database (DAN DB) now including specific questionnaires for data collection provided 137,421 electronically recorded recreational dives made by 5,907 divers (males 86.7%, females 13.2%) over 9 years and between 2.2 and 192 msw depth, using both open circuit scuba and rebreathers, up to an altitude of 2,400 m above sea level. There were 628 DCS cases reported, sometimes as a single event fora diver, and sometimes repeatedly occurring in the same diver (up to seven incidents per single diver). Results: Dives which finished with DCS were different than those without DCS, by several factors including number of dives in series, surface interval, maximum depth and run-time, as well as DSSG factor (DAN Surface Supersaturation Gradient), but most of them could be described as acceptably safe, according to the current decompression algorithms. Preliminary analysis of persona! factors confirms that age and BMI play a role in DCS. lnterestingly, in our materiai, DCS was observed more in females (1.25%) than in males (0.375%). Multifactorial analysis will help in identifying additional risks relateci with diving conditions, underwater stress, and well-being condition before diving. Conclusion: The DAN DB analysis shows that most dives were made in a "safe zone," but our data also clearly show a "gray area" and fai Iure in the current algorithms ability to "mathematically" predict DCS. Other risk factors, both individuai and environment relateci also seem to influence the possibility to develop DCS, irrespective of bubble formation, showing the importance of non-strictly decompression relateci risk factors, but rather individuai susceptibility and/or environment relateci variables, influencing the dive's outcome or possibly enhancing the effects of bubbles. The Data coming for our DB Analysis are now being used to develop a novel experimental model aimed at a statistica!, epidemiologica I and probabilistic approach to individualized safe decompression.

Background: The present study was designed to observe if different decompression profiles, calculated as a function of tissue supersaturation during ascent, would result in significantly different outcomes, measured through different physiological stress indicators, even in the absence of symptoms of decompression sickness.