The subjects included in the study were 10 medically fit, male, recreational divers (mean age, 44 ± 7 years; range, 33 to 54 years; mean weight, 79 ± 11 kg; range, 58 to 96 kg; mean height, 177 ± 5 cm; range, 170 to 186 cm; mean body mass index, 25 ± 3; range, 19.8 to 31.7). In accordance with French law concerning biomedical research, the divers gave informed consent and protocol was approved by the institutional ethical committee. Each subject passed a screening examination, including physical examination and medical history. All volunteers denied taking any medication at the time of the study. Diving was the only physical activity performed by eight of the subjects. Diving took place in sea water at a mean depth of 34.3 ± 2.7 m of sea water (113 ± 9 feet) and a mean duration of 25 ± 4 min.
The breathing mixture was air (N2O2), and the decompression procedures were conducted in accordance with the 1992 French Labor Ministry decompression table. The descent time was included in the dive time, the ascent was linear, and the ascent rate up to the decompression stop was 9 m of sea water per minute (29.52 feet/min). The control was made by using a chronometer, a depth meter, and a dive computer equipped with a bar graph of ascent (Maestro Pro; Beuchat; Marsailles, France). website
This dive profile is usually performed by recreational divers in the Mediterranean Sea, and it has been studied by our team in previous work. It induced a rather important bubble grade in most divers. The maximum bubble count was reached 60 min after surfacing.
The divers were equipped with neoprene diving suits; the thickness of the suits was in accordance with the temperature of the water. None of the divers reported suffering from the cold. The divers had to reduce exertion as much as possible before and after diving. After diving, the subjects were undressed and were taken to the laboratory. The divers did not have a warm shower before the end of the Doppler echography, so the results were not biased.