Hypertension, or high blood pressure, is one of the most common medical conditions seen in the diving population - no surprise, really, since it is a common medical condition in the general population. Strict criteria for hypertension can vary depending on the reference cited, but normal blood pressure is generally accepted to be a systolic pressure below 140 and a diastolic pressure below 90 mm Hg, depending on age (cited as systolic first and diastolic second - e.g. "120 over 80," by your doctor). A thorough medical evaluation should be performed to find a treatable cause for hypertension; in most cases, however, none will be found.
Basically, two different sets of complications face a person with hypertension: short-term and long-term. Short-term complications are generally due to extremely high blood pressure; the most significant is the risk of a stroke due to rupture of blood vessels in the brain (called a cerebrovascular accident). Long-term detrimental effects are more common: they include coronary artery disease, kidney disease, congestive heart failure, eye problems and cerebrovascular disease.
Fitness and Diving Issue
As long as the individual's blood pressure is under control, the main concerns should be the side effects of medication(s) and evidence of end-organ damage. Divers who have demonstrated adequate control of blood pressure with no significant decrease in performance in the water due to the side effects of drugs, should be able to dive safely.
A recent report in a diving medical journal citing several episodes of acute pulmonary edema (i.e., lungs congested with fluid) in individuals with uncontrolled hypertension while they were diving. Regular physical examinations and appropriate screening for the long-term consequences of hypertension such as coronary artery disease are necessary.
Medication Used in Treatment
Mild hypertension may be controlled with diet and exercise; however, medication is often necessary. Many classes of drugs are used to treat hypertension, with varying side effects. Some individuals must change medications after one drug appears to be or becomes ineffective. Others might require more than one drug taken at the same time to keep the blood pressure under control.
Classes of drugs known as beta-blockers often cause a decrease in maximum exercise tolerance and may also have some effect on the airways. This normally poses no problem for the average diver. ACE (angiotensin converting enzyme) inhibitors are the preferred class of drugs for treating hypertensive divers; a persistent cough is a possible side effect.
Calcium channel blockers are another choice, but lightheadedness when going from a sitting or supine position to standing may be a significant side effect. Diuretics are also frequently used to treat hypertension. This requires careful attention to hydration and electrolyte status. Most anti-hypertensive medications are compatible with diving as long as the side effects experienced by the diver are minimal and their performance in the water is not significantly compromised. Any diver with long-standing high blood pressure should be monitored for secondary effects on the heart and kidneys.
For more information on cardiovascular conditions, see the complete article by Dr. James L. Caruso on Cardiovascular Fitness and Diving from the July/August 1999 issue of Alert Diver.