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Effects of fluid loss on the physiology of closed-circuit rebreather divers after 100- and 45-metre dives
Laura Tuominen1,2,3, Richard Lundell2,3, Costantino Balestra4,5,6, Tomi Wuorimaa3, Lauri Koponen3, Sofia Sokolowski2, Anne Räisänen-Sokolowski2,3,7
1 Department of Emergency, Emergency Medical Services, Centre for Prehospital Emergency Care, Tampere, Finland
2 Department of Pathology, Helsinki University Hospital, and Helsinki University, Helsinki, Finland
3 Centre for Military Medicine, Finnish Defence Forces, Helsinki, Finland
4 Environmental, Occupational, Aging (Integrative) Physiology Laboratory, Haute Ecole Bruxelles-Brabant
(HE2B), Brussels, Belgium
5 Physical Activity Teaching Unit, Motor Sciences Department, Université Libre de Bruxelles (ULB), Brussels, Belgium
6 DAN Europe Research Division (Roseto-Brussels), Brussels, Belgium
7 DAN Europe Foundation Research Division (Roseto-Helsinki), Helsinki, Finland
Corresponding author: Dr Laura Tuominen, Department of Emergency, Emergency Medical Services, Centre for Prehospital Emergency Care, Tampere, Finland
ORCiD: 0000-0003-0826-4679
Keywords
Decompression sickness; Dehydration; Diving medicine; Risk management; Technical diving; Vascular gas emboli
Abstract
(Tuominen L, Lundell R, Balestra C, Wuorimaa T, Koponen L, Sokolowski S, Räisänen-Sokolowski A. Effects of fluid loss on the physiology of closed-circuit rebreather divers after 100- and 45-metre dives. Diving and Hyperbaric Medicine. 2025 December 20;55(4):391−397. doi: 10.28920/dhm55.4.391-397. PMID: 41364863.)
Introduction: Diving induced immersion diuresis predisposes divers to dehydration. Dehydration is considered a risk factor for decompression sickness (DCS) but there is very little evidence to prove it. Dehydration also potentially modifies venous gas emboli (VGE) formation and impairs endothelial function. The purpose of this study was to report the effects of fluid loss during a dive on the diver’s physiology.
Methods: Nine divers performed a 45 metre fresh water (mfw) and a 100 mfw dive with predetermined dive profiles. Body weight was measured before and after the dive. Post-dive detection of VGE was performed according to the extended Eftedal-Brubakk scale. We also measured haematocrit and flow mediated dilation before and after the 100 mfw dives.
Results: After a 68-minute dive to 45 mfw, median weight loss was -1.1 kg, (IQR -1.2, -1.0; range -2.0, -0.6), P = 0.009 and VGE were detected in all divers. After a 170-minute dive to 100 mfw, median weight loss was -1.5 kg (IQR -1.8, -1.1; range -2.2, -0.8), P = 0.009 and VGE were detected in seven divers. Weight loss after the dive was statistically significant and there was a negative correlation between weight loss and bubbling after the 45 mfw dives. None of the divers suffered any symptoms of DCS.
Conclusions: We found significant weight loss after both decompression dives but there were no clinical DCS symptoms in any of the divers. This study does not offer new evidence supporting the notion that dehydration increases decompression stress in divers.
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