High Blood Pressure - can I dive?

High blood pressure, also called hypertension or essential hypertension, is one of the most common medical conditions in individuals over 40 years of age. Not surprisingly, it is just as common amongst divers. High blood pressure carries certain risks that everyone, especially divers, should be aware of:

By way of an analogy: Hypertension may be thought of as the temperature of your car engine. The cooler the better, unless it stops (as would be the case with fainting from low blood pressure or feeling tired all the time). Coversely, the hotter it runs, the more the wear and tear results; eventually a gasket may go (as would be the case of a heart attack, a stroke, or a ruptured aortic aneurism). So, how high is too high?

Defining normal varies: There are individual norms and there are population norms. In general, though, a systolic blood pressure of more than 140 millimeters mercury (which is the pressure when the heart contracts and forces blood into the systemic circulation) and a diastolic blood pressure greater than 90 mmillimeters mercury (that is the elastic recoil in the blood vessels when the heart relaxes and the blood is held in suspension by the closed heart valves) would be considered high if it is the average blood pressure. Blood pressure varies during the day and night, so often a 24-hour blood pressure assessment is used to calculate the average - especially when patients are nervous at the doctors office!

Treating high blood pressure that is not due to other medical problems - such as diabetes, certain tumors or kidney disease - is usually simple and effective. Most recommendations start with a diuretic, which encourages fluid loss. The problem is that certain minerals may also be lost (such as potassium) causing cramps. For divers, and pilots, the most common first choice is a so-called angiotensin converting enzyme blocker or ACE inhibitor. These drugs are inexpensive and safe, but they may cause coughing in some individuals. A modified version of the ACE drug, called an angiotensin receptor blocker (such as Cozaar), may then be used. There are also calcium channel blockers, alpha blockers and beta blockers which affect small blood vessel diameter and heart rate and strength of contractions in ways that lower blood pressure. The biggest concerns associated with these medications are a lowering of exercise tollerance or fainting. Swelling of the legs and ankels may also occur.

Fitness and Diving Issue
As long blood pressure is controlled; exercise capacity is unaffected; and the heart, brain, kidneys and blood vessels are not damaged so as to impose risk of sudden incapacitation, diving is not a problem.

We obviously recommend that a doctor - preferably one familiar with diving medicine - assist you with selecting and monitoring your blood pressure if you are a diver.

If you have any additional questions, contact DAN via e-mail - medical@dansa.org, or call the hotline on 0800 020111, for more information.