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NAUI Master Scuba Diver 140 Diving Physiology lying cardiovascular disease. Both heart attack and stroke can result from the process of arteriosclerosis. The word root “arterio-” refers to your arteries, and “sclerosis” means a thickening or hardening. You may know that word from a different disease, “Multiple Sclerosis,” where many (or multiple) hardenings (scleroses) destroy nerve coverings in the central nervous system. In arteriosclerosis, your arterial walls thicken, harden, and lose elasticity which reduces blood flow. Past a certain point, your damaged blood vessels cannot supply your body’s demand for oxygen. Cardiovascular disease is not just something that happens to older people. The arteriosclerotic process begins in childhood with poor eating habits and sedentary lifestyle. By the time symptoms first occur in adulthood, your arteries can be nearly blocked. For about half of the people who have cardiovascular disease, the first symptom is a heart attack. Sudden death is the result in about half of these cases. Blood vessels that clog from the cardiovascular disease process can clog up all over your body, not just in your heart. One place is your brain. Blockage of a blood vessel to the brain, blocking oxygen supply, is called a stroke, or “brain attack.” Stroke can also occur when an unhealthy blood vessel ruptures, causing bleeding into the area. Stroke causes sudden loss of brain function. Effects depend on where in your brain the stroke occurs, and how much brain damage occurs. Effects range from reduction or loss of sensation, vision, muscular control, or consciousness to dizziness, slurred speech, or loss of memory, and other faculties. There are four major risk factors for cardiovascular disease: 1. High blood cholesterol 2. High blood pressure (hypertension) 3. Smoking 4. Lack of exercise Other risk factors are being male, family history, diabetes, high body fat, and how much fat you eat, particularly animal fat. Even with no other risk factors present you may have a sudden heart attack if you use cocaine. If you have had a heart attack or stroke, it may be possible to resume diving. Although there is not unanimous agreement among physicians, many feel that diving is acceptable after heart attack if you can perform at a moderately high level on a stress test without pain, abnormal ECG, or irregular blood pressure response. Diving after stroke depends on remaining symptoms and exercise tolerance. Cardiovascular disease is mostly preventable. Get regular aerobic exercise. Don’t smoke. Keep your blood cholesterol and blood pressure in healthy ranges. Eat plenty of vegetables and fiber. Limit fat consumption. Get regular checkups. Lung Disorders Lung disorders prohibit diving if they prevent, or some would say reduce in any way, passage of air out of your lungs or limit your exercise tolerance. Infection, environmental pollution, and smoking can create lung problems that can possibly interfere with your diving health. Temporary conditions such as bronchitis, colds, allergies, and flu may restrict your airways enough to prevent expanding air from being vented during a scuba diving ascent. Even though you breathe normally, ascend slowly, and have normally healthy lungs, these conditions could possibly create enough blockage to result in lung overexpansion injuries. Asthma, chronic bronchitis, emphysema, and other obstructive lung diseases are among the most commonly stated contraindications, with asthma the most commonly debated. According to some authorities, people with asthma are overrepresented in the accident population. Others state that since flow obstruction with asthma is variable, case-by-case decisions are called for, rather than blanket disqualifications. Childhood asthma is often outgrown, so adults with a history of asthma may also receive medical clearance to dive. Chest x-rays, pulmonary function tests, and listening to your chest with a stethoscope all shed some light on the condition of your lungs, but only at the time of the exam. Small areas of abnormal lung may not be detectable, yet could possibly contribute to lung overpressure injuries. There is various discussion in the medical com


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