DAN Medical Frequently Asked Questions
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>Hypertension, or high blood pressure, is a common medical condition in the general population as well as among divers. Blood pressure is a measure of the force with which blood pushes outward on the arterial walls. A blood-pressure reading is a ratio of two numbers. The top number is the systolic pressure, when your heart is beating, and the bottom number is the diastolic pressure, when your heart is resting between beats. The unit of measurement for a blood-pressure reading is millimeters of mercury, which is abbreviated as "mmHg"; a normal reading is 120/80 mmHg, often referred to as "120 over 80."
>The criteria for a diagnosis of hypertension vary slightly from country to country and even from one reference to another. The table below shows the most common criteria used in the United States.
- 78 million American adults (or 31% — almost 1 in 3) have hypertension.
Mild hypertension can often be controlled with diet and exercise; however, medication may be necessary to keep blood pressure within tolerable limits. Many classes of drugs are used to treat hypertension, and they have varying side effects. Some individuals must change medications after one drug appears to be or becomes ineffective. Others might need to take more than one drug at a time to keep their blood pressure under control.
- 69% of those who have a first heart attack, 77% of those who have a first stroke, and 74% of those with chronic heart failure have hypertension; it is also a major risk factor for kidney disease.
- 348,000 American deaths in 2009 were attributed, as either a primary or contributing cause, to hypertension.
- $47.5 billion annually is spent on direct medical expenses related to hypertension.
- $3.5 billion annually is lost in productivity due to hypertension.
- Only 47% (less than half) of those with hypertension have the condition under control.
- 30% of American adults have prehypertension.Sources: U.S. Centers for Disease Control and Prevention; and American Heart Association
Two kinds of complications face a person with hypertension: short term and long term. Short-term complications generally result from extremely high blood pressure; the most significant is the risk of a stroke (also called a "cerebrovascular accident") due to the rupture of a blood vessel in the brain. Long-term detrimental effects are more common; they include coronary artery disease, kidney disease, congestive heart failure, eye problems and cerebrovascular disease.
>A class of antihypertensive drugs known as beta blockers may cause a decrease in maximum exercise tolerance and may also have some effect on the airways. These side effects normally pose no problem for the average diver. Another class of antihypertensives, known as angiotensin-converting enzyme (ACE) inhibitors, may be preferred for divers, though a persistent cough is a possible side effect of ACE inhibitors. Calcium channel blockers are another choice, but a potential side effect of these drugs is lightheadedness upon going from a sitting or supine to a standing position.
>Diuretics — drugs that promote the production of urine — are also frequently used to treat hypertension. Their use requires careful attention to maintaining adequate hydration and to monitoring electrolyte levels in the blood.
>As long as an individual's blood pressure is under control, the main concerns regarding fitness to dive are side effects of any medication(s) and evidence of damage to the major organs. Most antihypertensive drugs are compatible with diving as long as side effects are minimal and the diver's performance in the water is not significantly compromised. In addition, a diver with long-standing hypertension should be monitored for evidence of associated damage to the heart and kidneys.
>Divers who demonstrate adequate control of their blood pressure and who show no significant decrease in their performance in the water due to drug side effects should be able to dive safely. However, it is important that such divers have regular physical examinations, including screening for long-term consequences of hypertension, such as coronary artery disease.