Circulatory adaptations in sponge fishermen (skin divers)

Abstract About three hundred men living on the island of Kalymnos, Dodecanese (Greece), are professional sponge fishermen, working without special apparatus as skin divers off the coasts of Cyrenaiki and Tripolis in North Africa during the summer, and the coasts of the Dodecanese and Egypt during the winter time. They work ten months a year, from 8 a.m. to 5 p.m. every day, i.e., during the time the sea bottom is illuminated by the sun, and one can discern the sponge colonies, found at a depth of 50 to 70 meters, as small gray spots. The sponge fishermen dive continuously during the day's work, without taking any food in order to avoid vomiting and loss of efficiency. They perform 50 to 120 dives a day with an apnea lasting from one to two and one-half minutes. Their ages range from 16 to 56 years, most of them being between 20 and 35 years old. In an attempt to evaluate the circulatory adaptions in these persons, we have undertaken the present investigation. Our attention was focused mainly on the right side of the heart which, in our opinion, must be influenced by such a long voluntary apnea during a great part of their lives.