The effect of two consecutive dives on bubble formation and endothelial function in rats.
BACKGROUND
Gas bubble formation during and after decompression is considered to be the main initiator of decompression sickness (DCS). Compressed-air workers have been reported to acclimatise to the working environment and hence have a reduced risk of DCS, but the exact nature of the adaptation is not known. In the present study, we investigated the effect of two consecutive dives, separated by a 24-hour surface interval, on bubble formation and endothelial damage in rats.


METHODS
A total of 30 rats were divided into four groups, one control group and three dive groups with different dive profiles, of which two of the groups had two dives. The amount of bubbles in the pulmonary artery was estimated by ultrasound for one hour after surfacing, and tension measurements were performed in vitro on segments of the abdominal aorta following sacrifice of the animals.


RESULTS
No significant differences between the groups were found in endothelial function or bubble grade. However, animals that died immediately after the dive, irrespective of grouping order, had lower acetylcholine-induced dilatory responses in the aorta than surviving rats.


CONCLUSIONS
Bubble formation and endothelial function among rats were not significantly affected by exposure to consecutive dives 24 hours apart. An adaptive, protective effect of repeated dives was hence not seen in this animal model.
Research student, Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Olav Kyrres gt. 3, N-7489 Trondheim, Norway, Phone: +47-(0)91-513615, Fax: +47-(0)73-597940, E-mail: marianne.b.havnes@ntnu.no.
Marianne B
MB
Havnes
Andreas
A
Møllerløkken
Alf O
AO
Brubakk