Diving Medicine

SR. Dive, food, and exercise effects on blood microparticles in Steller sea lions (Eumetopias jubatus): exploring a biomarker for decompression sickness..—Re-cent studies of stranded marine mammals indicate that exposure to underwater military sonar may induce pathophysiological responses consistent with decompression sickness (DCS). However, DCS has been difficult to diagnose in marine mammals. We investigated whether blood microparticles (MPs, measured as number/l plasma), which increase in response to decompression stress in terrestrial mammals, are a suitable biomarker for DCS in marine mammals. We obtained blood samples from trained Steller sea lions (Eumetopias jubatus, 4 adult females) wearing time-depth recorders that dove to predetermined depths (either 5 or 50 meters). We hypothesized that MPs would be positively related to decompression stress (depth and duration underwater). We also tested the effect of feeding and exercise in isolation on MPs using the same blood sampling protocol. We found that feeding and exercise had no effect on blood MP levels, but that diving caused MPs to increase. However, blood MP levels did not correlate with diving depth, relative time underwater, and presumed decompression stress, possibly indicating acclimation following repeated exposure to depth. sea lion; decompression; stress; apnea; diving; bubbles THE PURPOSE OF THIS STUDY was to improve understanding of physiological responses to diving in a breath-hold diving marine mammal, with a particular focus on the pathophysiology of decompression sickness (DCS). DCS is a systemic patho-physiological process that occurs naturally after tissues become supersaturated with N 2 under high atmospheric pressure. In humans, DCS can also occur when N 2 or some alternative gas is used to dilute O 2 in breathing mixtures during activities such as deep-sea diving, high-altitude aviation, and space exploration. Most studies of DCS are performed with terrestrial mammals. We therefore hypothesized that a comparative physiological approach studying bona fide diving mammals would add valuable insight into the physiology of decompression. Such an approach may yield insights into the potential physiological traits that allow breath-hold diving animals to perform prolonged apneas to great depths without apparent pressure-related problems. There are data indicating that diving mammals may sustain DCS, at least when they are subjected to atypical stresses (11, 16, 17). Recent necropsy reports have suggested a link between mass stranding of beaked whales and the use of naval midfre-quency sonar (10). The whales experienced symptoms that were similar to those caused by inert gas bubbles in human divers (4). These reports have increased the concern that anthropogenic sound, such as that created by military sonar or during seismic exploration, may harm marine animals. Specifically , it has been suggested that alteration in physiology or diving behavior may increase the risk of DCS (3, 15). For instance, blood bubble formation has been noted in some turtles that were trapped underwater and hauled rapidly to the surface. Those that received recompression treatment recovered and were released, thereby confirming a clinical diagnosis of DCS in a diving vertebrate (12). Bubble formation is believed to be a crucial event in the etiology of DCS, but the role bubbles play in the disease process remains unclear (22). As more is learned about DCS, it has become apparent that some of the symptoms are similar to those of other disease states (18, 35, 36). There are a few well-defined risk factors that increase the probability of DCS, such as increasing dive duration, dive depth, ascent/decompression rate, body mass, and breathing gas (8, 19, 20, 37). Recent studies have shown that micropar-ticles (MPs) are elevated with decompression stress (31, 32). MPs are cellular fragments between 0.3 and 1 m in size that are shed from various cells. MPs derived from platelets are known to activate leukocytes and cause aggregation and can stimulate proinflammatory cytokines. MPs derived from de-compression stress have been shown to specifically activate neutrophils and cause vascular damage (32). MPs correlate with depth of diving in mice (32), but correlate poorly with depth in humans (31, 33). Studies have also evaluated the effect of exercise on bubble and MP production in human scuba divers. Exercise can increase the number of circulating MPs slightly, whereas diving has a much greater effect and is also impacted by the gas used during the dive (31). The question of potential causal relationships among bubbles , MPs, platelet-neutrophil interactions, and neutrophil activation remains obscure (30). Our study aimed to examine the relationship between decompression stress (depth and time underwater) and blood MP levels in Steller sea lions in a controlled diving experiment, in the context of diving, feeding,

Background: Recreational scuba diving has been authorized for type 1 diabetics over 18 years old – the age
of majority in France – since 2004, but it remained forbidden for younger diabetics by the French underwater federation (FFESSM). Here, we present a study to evaluate:
– the conditions under which diving could be authorized for 14- to 18 year olds with type 1 diabetes;
– the value of continuous glucose monitoring (CGM) while diving. A secondary objective was to monitor the impact of diving on the teenagers’ quality of life.
Subject and methods: Sixteen adolescents (14–17.5 years old) were included. Diabetes was known for 6 years (range, 1–14) and Hb1Ac was 9.0% (range, 7.7–11.9). The study was conducted in Mayotte with both capillary glycemia (CG) and CGM measurements taken during five dives.
Results: The average CG prior to diving was 283 mg/dL and decreased by 75 +or- 76 mg/dL during the dive.
No hypoglycemia occurred during the dives and four episodes occurred after. Glycemia variations during
dives and for the overall duration of the study were greater than for adults, most likely due to the general
adolescent behavior, notably regarding diet and diabetes management. CGM was greatly appreciated by the
adolescents. They had an overall satisfactory quality of life. No significant variations were observed during
the entire course of the study.
Conclusions: Although in need of further studies, these preliminary results show that CGM can be used
while diving. CGM records show a continuous decrease of glycemia during dives. Based on these results,
the French underwater federation has now authorized diving for adolescent type 1 diabetics following a specific diving protocol that includes HbA1c < 8.5%, autonomous management of diabetes by the adolescent, reduction of insulin doses, and target glycemia prior to the dive > 250 mg/dL.