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AD 2016 Q2

As we pointed out in the spring 2013 edition of the Alert Diver, even being a dive buddy has potential legal implications. So, to bump this up a notch, what about the diver training organisations themselves? Where do they stand? How do they relate to South African law? Are they all considered the same under our legal system in spite of the differences in organisational structures and training programmes? How does this affect their respective instructors and trainee divers from a legal perspective? These are not exactly simple questions. It is certainly true that the respective training organisations differ in a number of ways. However, this does not imply that there are necessarily differential legal implications for each of them. In fact, under South African law, the legal principles are common in all matters. Therefore, if you suffer a loss and you (or your estate in the case of a fatality) wish to recover damages, the legal principles would be applied commonly; whether you are driving or diving. Although not a frequent occurrence, there have been quite a number of law suits associated with diving injuries and damages in South Africa. This is not surprising, as the occurrence of law suits is really a function of “numbers”. As training increases, so do the chances of injuries and, with it, the chances of legal recourse. So, it remains wise to insure yourself, your equipment or your business in a proper and effective way. But before getting back to the potential differences amongst the training agencies, let’s first explore the foundational legal principles on which any civil claim would be adjudicated: inherent risk, negligence and duty to take care.

[ Dietary Supplements

[ Dietary Supplements and Healthy Foods for Divers [ BY PETAR DENOBLE, M.D., D.Sc . RONSTIK/ISTOCKPHOTO.COM Dietary supplements are popular among health- and fitness-conscious people, including recreational divers. Divers often ask about the possible benefits and adverse effects of supplements, used for either general wellness or protection from certain diving injuries. Dietary supplements are clearly helpful to people with a chronic deficit of specific nutrients such as vitamin C (scurvy) or vitamin D (rickets), but effects of supplements in healthy people who eat a balanced diet are less obvious. The large number of supplements available today far exceeds our cumulative scientific capacity to study them all, and so use of supplements grows beyond evidence of their benefits. OXIDATIVE DAMAGE Antioxidants are molecules found in cells throughout the body where they help control the free radicals that result from oxidative metabolism. Free radicals are reactive oxygen species (ROS): chemically reactive oxygencontaining molecules that may damage cells and tissues. Most ROS are successfully contained by antioxidants. Some oxidative damage to cells occurs all the time, but most is repaired. Sustained damage, however, may cause genetic changes, various diseases and faster aging. Breathing hyperoxic gas mixes — those containing more than 21 percent oxygen — for prolonged periods causes oxidative damage in divers. This can affect the eyes (causing myopia), the lungs (causing difficulty breathing) and/or the central nervous system (causing various symptoms, including convulsions). After decades of research we have not managed to prolong the time of symptom-free diving with hyperoxic breathing gases; instead we have learned there are limits on oxygen exposure that divers must obey. In addition to hyperoxic breathing gas, factors such as immersion, cold, hypoxia and exertion may increase oxidative stress. Accumulation of low-level oxidative damage over time may damage DNA and possibly reduce longevity. One manifestation of oxygen damage is loss of arteries’ self-regulatory capacity, also known as endothelial dysfunction. The endothelium, the inner layer of the arteries in contact with the blood, releases nitric oxide (NO), which relaxes the smooth muscles in the arterial walls to increase their diameter and change their tone. These mechanisms increase blood flow and/ or reduce blood pressure. 82 | SPRING 2016

FLOW-MEDIATED DILATION A noninvasive test called flow-mediated dilatation (FMD) can evaluate endothelial function by measuring the increase in diameter of an artery after five minutes of occluded circulation. Normally the diameter of an artery increases when circulation is reestablished, but not so with endothelial dysfunction. Several factors, including exercise and eating various foods, can elicit transitory endothelial dysfunction. It is suspected that repeated endothelial injury may contribute to atherosclerosis and acute heart conditions. Using FMD, researchers found endothelial dysfunction in divers during open-water diving and in hyperbaric chambers. Studies showed that FMD reduction was more pronounced after nitrox dives but practically unchanged after successive dives and air dives. Variability of response was large, however, and there is no obvious link between FMD findings and cardiovascular disease in divers. Diminished endothelial function is a reality of aging, and diving has not been proven to exacerbate it. ANTIOXIDANTS Antioxidants include vitamins such as vitamin A and vitamin C as well as minerals such as selenium, plant products such as flavonoids and animal products such as melatonin and omega-3 fatty acids. Antioxidants are used in attempts to control oxidative stress and prevent related diseases. The big three are vitamin E, vitamin C and glutathione. Numerous other small molecules — including polyphenols, carotenoids, bilirubin and uric acid — function as antioxidants. These are contained in foods and drinks including meat, citrus, chocolate, tea and wine. In addition to supporting many bodily functions, vitamin E (tocopherol) is also an antioxidant, readily reacting with and inactivating ROS. Used vitamin E is recycled with the help of vitamin C. Natural sources of vitamin E are abundant, and normal nutrition provides enough to meet physiological needs. Larger doses of vitamin E have been used in efforts to treat various diseases such as hypertension, heart disease, cancer and more, but studies have not found any unequivocal proof of benefits. High doses of vitamin E can lead to hypervitaminosis E with possible vitamin K deficiency and increased risk of bleeding. Vitamin E was one of the first supplements used to try to prevent acute oxygen toxicity in humans, but it was unsuccessful. Vitamin C enhances wound healing. Animal studies have shown that vitamin C can prevent vasoconstriction of coronary arteries caused by hyperoxia. In human studies, vitamin C blocked hyperoxic vasoconstriction and maintained forearm bloodflow. Researchers studied possible protective effects of vitamin C and vitamin E in healthy divers. Divers who received a single dose of 2,000 mg of vitamin C and 400 IU of vitamin E two hours prior to diving had normal endothelial function, and those who received a placebo exhibited endothelial dysfunction. In another study, divers who received 1,000 mg of vitamin C and 400 IU of vitamin E daily for four weeks showed attenuated postdive decrease in FMD. In the same studies, vitamins prevented changes in other measurements of cardiovascular function that seem to occur regularly in diving. VANATCHANAN/SHUTTERSTOCK Oxidative Stress The energy necessary to sustain life is produced within cells by oxidative metabolism. This process breaks down complex molecules from micronutrients, freeing their chemical energy and storing it in ready-to-use packages called adenosine triphosphate (ATP). This can occur through several pathways, but the only sustainable process includes oxygen as a receiver of electrons freed from the energy-rich chemical bounds. In that process, various forms of very reactive oxygen-containing molecules arise. Called reactive oxygen species (ROS), or oxygen radicals, these molecules play important roles in health and disease. The amount of ROS increases with physical activity and intensity of metabolism. Exposure to hypoxia, hyperoxia and ionizing radiation may also increase production of ROS. White blood cells in contact with bacteria release huge amounts of ROS, which kills bacteria. Surplus ROS can be neutralized by various protective substances called antioxidants. Oxidative stress is a condition in which the amount of generated ROS exceeds existing antioxidant capacities. Mild oxygen stress can improve bodily functions (promoting muscle growth, for example), but excessive stress can cause various diseases and speed up aging. Efforts to prevent diseases and extend life include strategies to reduce oxidative stress and increase the availability of antioxidants in the body. ALERTDIVER.COM | 83

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