Continuous real-time monitoring and recording of glycemia during scuba diving: pilot study

Introduction: Insulin-dependent diabetes has been considered a scuba diving contraindication. This is currently being reconsidered for well-controlled dia- betes. We developed a real-time continuous glucose monitor (CGM) to check glycemia, or blood glucose (BG), during diving, both for prospective studies and to increase diabetic diver safety, allowing for real-time control of glycemia and hypoglycemia pre- vention. To ensure CGM measurement accuracy we tested the method under hyperbaric conditions.

Materials and methods: Two experienced diabetic divers were studied during a one-week diving cruise. BG was monitored every five minutes on every dive, by a dedicated CGM, and values were visible to the divers throughout their dives. The mean of relative difference (MRD) between CGM and capillary blood glucose was calculated. Measurement accuracy was assessed according to ISO guideline 15197 and by Clarke Error Grid (CEG) analysis.

Results: Both divers showed gradual BG decrease during diving. Hyperbaric chamber accuracy tests showed two of 26 MRD values (7.7%) slightly exceed- ing the ISO-15197 allowed difference (5%). However, our data suggest that this discrepancy may have been an artefact.
Discussion: Our data (even limited to two subjects only) agree with the current literature showing that also in our investigated subjects diving does not imply significant risks of hypoglycemia. The use of a real-time CGM by diabetic divers during their dives can provide immediate information on BG values and trends, thus significantly improving diving safety. The accuracy tests comparing continuous glucose monitoring (CGM) and capillary blood glucose mea- surement (CBM) data recorded under hyperbaric conditions showed that data recorded under pressure are very close to the ISO-15197 and CEG acceptable limits.