Condition: Diabetes mellitus (DM) is a disorder of the endocrine system, manifested by one of two things: an insufficient production of insulin or the resistance of the body's cells to the actions of insulin despite normal or high levels. People with DM often have excessively high blood glucose (BG), called hyperglycemia, or an excessively low BG, better known as hypoglycemia.
Diabetes mellitus itself has two major forms: Insulin-requiring diabetes (IDDM, Type 1),* for which insulin must be given by injection to control blood sugar levels; and non-insulin-dependent diabetes (NIDDM, Type 2), which may be controlled by diet or by oral medications (oral hypoglycemic medications).
The main risk to the diver is the occurrence of hypoglycemia, that can manifest itself as confusion, sweating, rapid heartbeat, unconsciousness and even death. High blood sugar levels, or hyperglycemia, may also cause unconsciousness, although this usually develops much more slowly than hypoglycemia. Impaired consciousness underwater leads to almost certain death. Although hypoglycemia occurs most commonly in Type 1, it can also occur in individuals taking oral hypoglycemic medications. Hypoglycemia experienced during a deep dive may be wrongly perceived as nitrogen narcosis.
Although hypo- or hyperglycemia can occur daily, other problems can develop over the long term, in persons with diabetes. These maladies include: retinopathy (alterations in visual acuity); disorders of the kidneys; coronary artery disease; and changes in the nervous system, including abnormal nervous conduction and atherosclerosis, that can cause poor circulation in the limbs.
Fitness and Diving: Divers with diabetes are at risk of sudden loss of consciousness. This carries the ultimate risk of drowning and implies additional risks for their dive buddies. Individuals with diabetes, however well the diabetes is controlled, should not be deemed as fit to dive without restriction. Those who meet certain criteria can dive provided they dive in accordance with detailed, specific procedures (See Diabetes & Diving: Current practices demonstrate that many with diabetes do take the plunge; By Guy de Lisle Dear, M.B., FRCA, Alert Diver, January / February 1997). Divers with diabetes should be examined periodically for complications of their disorder that may disqualify them on the grounds of additional risk.
Medication Used in Treatment: Sulphonylureas (drugs that posses hypoglycemic action) such as glipizide, glibenclamide, chlorpropamide and tolbutamide may interact with numerous other drugs used to lower BG.
There is a small risk of lactic acidosis which is markedly increased by any condition that reduces metformin clearance (acute or chronic renal impairment) or compromises oxygen delivery and predisposes to tissue hypoxia (acute or chronic respiratory or cardiovascular insufficiency) in persons with renal, liver or heart diseases.
Note: The acronym IDDM actually stands for the older term insulin-dependent diabetes mellitus, although the newer term for this condition is termed insulin-requiring diabetes mellitus, and is still represented as IDDM. The diabetes community currently is in transition between nomenclatures.