Apnea Diving

Men and women have been diving for thousands of years to gather a variety of products, including food, sponges, and pearls, to conduct salvage and military operations, and to explore. In 1911, one of the first freediving competitions was held when a Greek fisherman, Yorgos Haggi Statti, was offered a few dollars to dive and to rescue the anchor of an Italian ship which had become stuck in the Aegean Sea. The Italian ship was set free and Yorgos became known as the “father of freediving”. After World War II, breath hold diving became an international sport where athletes test the human limits of time, depth and distance. Exposure to excessive depths, though, can be very dangerous and cause a collapse of the lungs, cardiac arrest, blackouts, decompression sickness and, at worst, death. Whatever the reason for breath hold diving, its success depends on how a diver tolerates the physiological stress related to the depth and duration of dive. The human body has several adaptations under diving conditions, which stem from the mammalian diving reflex. These adaptations enable the human body to endure depth and lack of oxygen far beyond what would be possible without the reflex. Human diving response involves bradycardia, vasoconstriction of selected vascular beds with increase in blood pressure, changes in cardiac output and spleen contraction. Variety of studies frequently discussed parts of diving response. However, the concept of spleen contraction has recently been described as a property of diving response. The spleen serves as a dynamic blood cell reservoir which can be released into systemic circulation during exercise, diving or intermittent hypoxia. Since contraction of the spleen increases hemoglobin and hematocrit circulating in blood, than the O2transport will also be enhanced. In humans, the rapidity of spleen contraction indicates that the initial stimulation is likely neural in origin, but contraction may be sustained throughout the dive by circulating catecholamines released from the adrenal gland. Leucocytes and platelets accumulate in the human spleen to a much greater extent than erythrocytes, accounting for approximately 40% of both body populations. The destiny of these two populations during apnea induced spleen contraction is also the aim of our chapter.