Blood glucose changes and adjustments of diet and insulin doses in type 1 diabetic patients during scuba diving (for a change in French regulations)

Summary Objective In France, diabetic subjects were not allowed to dive. The principal risk is hypoglycemia during immersion. However scuba diving is allowed in many countries. To follow blood glucose changes, food intake and insulin adjustments in type 1 diabetic patients when diving, and to propose specific guidelines for such patients willing to practice recreational scuba diving. Methods Fifteen well-controlled (mean HbA 1c : 7.2 %) type 1 diabetic patients without complications were volunteer to dive under strict medical monitoring. They dove 8 times in 4 days in autumn at a depth of 20 meters, in 12°C to 16°C water. A strict protocol based on blood glucose was implemented to prevent hypoglycaemia. Results No case of hypoglycemia was observed and no faintness was reported underwater. Mean blood glucose before diving was 200 mg/dl (11 mmol/l). There was a mean fall in blood glucose of 40 mg/dl (2.2 mmol/l) during dives, a mean decrease in daily insulin doses by 19.3% on the last day. Daily energy intake was 3 225 Kcal in average. A continuous glucose monitoring (CGMS) was performed in one patient and showed a rather stable glycemia during immersion but a decrease within the 8 hours after. Conclusion When respecting a strict protocol to prevent hypoglycaemia, the risk of hypoglycaemia appears quite low. We recommend an ideal glycemic goal of 200-250 mg/dl (11-13.75 mmol/l) before immersion, a higher reduction of insulin doses (-30%) and taking carbohydrates on board in any case. The present data have recently led the French diving federation (FESSM) to allow type 1 diabetic patients to dive with some restrictive qualification requirements: dives within the “safety curve” (no decompression curve), in above 14°C water, depth limited to the median space range (6 to 20 meters), plus mandatory guidance by a diving instructor.