Deep-sea diving offers a breathtaking view of an enchanted world, but inadequate training and carelessness can literally take one's breath away. The condition called diving desease can cause serious damage to the body and even result in death, while less severe damage can be caused to the ears, nose, bones and other parts of the body. Hyperbaric oxygen treatment, which is used to treat the syndrome, is a recognized treatment not only for victims of diving accidents but also of disorders ranging from carbon monoxide poisoning to diabetic foot (caused by poor circulation and reduced nerve functioning) and avascular necrosis of bone. The health risks of diving and the potential of hyperbaric oxygen were both discussed at an unusual conference on diving medicine organized recently by the Israel Diving Federation at Hadassah University Medical Center on Jerusalem's Mount Scopus. It was in fact two separate but interlinked conferences - one for the general public that was standing-room-only in the Schacht Auditorium (attended by diving enthusiasts, mostly younger men), and a less-crowded conference for doctors one floor up. Some of the lecturers spoke at both gatherings, but tailored their terminology. THE LAYMEN'S conference began with complaints. Yuval Haft, chairman of the diving federation, noted a decline, not only in the number of active divers, but due to the ongoing closure of Israeli beaches because of land development and takeovers. Haft said that from 35,000 to 40,000 licensed Israeli divers a decade ago, their ranks have diminished to only about 5,500 today. This is a direct result of the inaccessibility of most former diving sites on the Israeli Mediterranean and Red Sea coasts, which forces aficionados to travel to Thailand, the Caribbean, Australia and other exotic sites. The distance has largely turned diving into a rich man's hobby. "There are very few places left between Rosh Pina and Eilat that are still open for diving," said Haft. Eilat has mostly become a place for training divers, as sites were closed after ecological damage was done to the reef. Today, there are 12 sites left, half as many diving clubs, and each, bemoaned Haft, is struggling to survive. "Of the Israeli divers still out there, we see fewer young people." To promote new interest in Israeli diving among local and foreign tourists, the diving federation has tried to persuade local authorities to agree to sink old ships and even a Boeing jet for sea creatures to populate and divers to explore, but so far it has not succeeded. Haft said the authorities still do not realize that diving off Israel's coasts - among the most beautiful undersea wonderlands in the world - has the potential to become a major industry. There are nine million divers in the US, with 1,000 major accidents a year, a tenth of them fatal, according to statistics presented at the conference. Many of the victims were exposed to a reduction in the pressure surrounding their body; in this case, the surfacing diver must enter a recompression chamber to avoid the bends. Sudden or intense pressure changes cause inert gases, mostly nitrogen, dissolved in body fluids and tissues to come out of solution and form gaseous bubbles. According to Henry's Law, when the pressure of a gas over a liquid is decreased, the amount of gas dissolved in that liquid will also decrease. ONE OF THE best practical demonstrations of this law is offered by opening a carbonated soft drink: When the cap is removed, gas is heard escaping, and bubbles can be seen forming in the liquid. This is carbon dioxide coming out of solution as a result of the pressure inside the container being reduced. Similarly, nitrogen is normally stored throughout the human body, but when the body is exposed to decreased pressures, such as during a scuba ascent, the dissolved nitrogen comes out of solution. If nitrogen comes out of solution too quickly, bubbles form in parts of the body, causing symptoms ranging from itching and rashes to joint pain to sensory failure, paralysis and death. Air emboli caused by other processes can have many of the same symptoms; decompression sickness (DCS) and air embolism are grouped together under the name decompression illness (DCI). DCS occurs not only among recreational divers, but also among undersea building workers. It was a major factor during construction of Eads Bridge over the Mississippi River near St. Louis in the 1870s, when 13 workers died from what was then a mysterious illness, and later during construction of the Brooklyn Bridge, where it incapacitated project leader Washington Roebling. The first documented cases of DCS were reported in 1841 by a mining engineer who noted pain and muscle cramps among coal miners exposed to air-pressurized mine shafts designed to keep water out. The first description of a case resulting from diving while wearing an air-pumped helmet was reported in 1869. A large pressure reduction is more likely to cause DCS than a small one. Repetitive dives within a few hours also increase the risk of DCS, which also occurs in pilots who ascend too fast. There are some reports indicating a higher risk of DCS as one gets older, and recent joint or limb injuries may predispose individuals to "the bends." Due to poor blood supply, nitrogen is stored in greater amounts in fat tissues: Although fat represents only 15% of a normal adult body, it stores over half of the dissolved nitrogen. The after-effects of alcohol consumption increase susceptibility to DCS. Diving can be dangerous for people with patent foramen ovale - a congenital hole between the arterial and venous atria of the heart (a defect that was discovered in the septum of Prime Minister Ariel Sharon after his first stroke). Such a hole allows blood with microbubbles to return to the body rather than pass through the lungs where the bubbles can be expelled normally, and this can cause serious medical problems. "The bends" accounts for about 60 of all DCS cases, with the shoulder being the most common site. Neurological symptoms are present in 10% to 15% of all DCS cases, with headache and visual disturbances the most common, with other symptoms including skin rashes, extreme fatigue, visual and balance disturbances, breathing difficulties, lack of strength, numbness, paralysis, unconsciousness and even death. ILAN GIALCHINSKY, a sixth-year student at The Hebrew University-Hadassah Medical school who has been diving since 1998, told the laymen that narrowed sinuses, ears clogged with cerumen (wax) and even dental fillings can cause complications in divers. While licensed divers usually use small computers to help them calculate safe times for descent and ascent, there are miscalculations, malfunctions and carelessness. "During the first few hours after a dive is completed, the person should be alert to any symptoms and go immediately to a doctor just in case, he said. "Don't wait if you suspect something is wrong." Dr. Avraham Ben-Ya'acov, an ear-nose-and-throat and head surgery specialist at Hadassah University Medical Center in Jerusalem's Ein Kerem, discussed ear problems in divers. Since the delicate eardrum separates the outer ear from the middle and inner ear, any difference in pressure can cause it to bleed or rupture, damaging the tiny bones, cochlea, semi-circular canal and auditory nerve that make hearing possible. Divers learn to clear the Eustachian tube that introduces air from the outside, but this is not always possible if there is a blockage, and an "explosion" or "implosion" of the eardrum may result. Divers who feel dizzy and suddenly can't hear properly must go immediately for medical help. The sinuses were the topic of discussion in the lecture by Dr. Menahem Gross, a department colleague of Ben-Ya'acov's at Hadassah. He explained that humans have four pairs of sinuses - the maxillary, frontal, ethmoid and sphenoid - which contain air. During diving, air pressure changes, and major changes can cause harm. Polyps and acute or chronic sinus infections can complicate this, he said. "Don't dive if you have a runny nose or a sinus infection," Gross advised. "If you do dive and notice bleeding, pain, dental pain or eye pain, go to a doctor immediately." At the doctors' conference, Dr. Yehuda Melamed - a diving medicine expert and licensed diver who heads the hyperbaric medicine and diving center at Haifa's Rambam Medical Center and Elisha Hospital - explained the benefits of high-pressure oxygen for certain medical problems. The lack of oxygen in acute conditions such as carbon monoxide poisoning or in chronic conditions such as diabetic foot can have severe repercussions; immediate exposure to high-pressure oxygen can mean all the difference. "The hyperbaric oxygen chamber is the only medical facility that makes possible the giving of oxygen as a medicine in the highest concentrations via respiration and its dissolution in the plasma, which increases oxygen concentration in the tissues." Dr. Daniel Reis, a Haifa colleague of Melamed, described avascular necrosis (AVN) of bone, a disabling condition affecting mostly young adults in the prime of their lives. It usually affects the femur (thigh) bone, and is a destructive, progressive, crippling disease. The femoral head, which connects to a joint, is especially vulnerable to necrosis due to lack of oxygen. Reis reported on his experience in flooding the extracellular fluid of the bone with high-pressure oxygen, which causes oxygen to stimulate the growth of blood vessels and bone cells. Patients with stage I or stage II AVN received as many as 60 daily sessions of 100% oxygen; in more than 81% of them, bone health and function returned to normal, compared to 17% in an untreated group. Other potential medical uses for hyperbaric oxygen are for treating radiation damage in cancer patients and healing decayed tissue in the limbs of patients with poor circulation.