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HYPERTENSION (High Blood Pressure)- What Is It & Why Is It So Bad?Untitled

In our biologic universe, oxygen is the fuel of life. All our cells and tissues depend on it. Our lungs capture it, and transfer it through the lung membranes into the wondrously complex hemoglobin molecules packed within the red blood cells. These red cells make up about 40 per cent of our blood volume, the "fluid of life". In order to deliver blood and its oxygen (and all the other essentials that comprise the other 60 per cent of blood) to all tissues, there must be a pumping mechanism that produces the flow. The heart is this blood pumping "machine". And, where there is flow, there is pressure. Remember from high school physics that pressure equals volume times resistance (P = V x R). With each contraction (beat), the heart pumps a volume (bolus) of blood into the first portion of the aorta, the large vessel that begins the arterial system. The "tone" of the aorta's vessel "wall" (composed of living and functional cells) provides resistance that can be quite variable. From the aorta branch out the smaller but still substantial arterial vessels that in the aggregate form what we call the "great" (meaning "large") circulation. Each of these great vessels also has its own variable resistance tone. These great vessels expand with each bolus of blood, and then contract, further propelling the arterial blood along throughout the body. All blood eventuallly returns to the heart and lungs through the venous system, but this a very low pressure system that is not involved in the disease of hypertension. The volume component of blood circulation is largely under the control of the kidneys, amazingly complex organs whose physiology captivates and challenges all medical students and physicians. (About 55 percent of blood is water. Cells other than red cells, proteins, salts, minerals, and other biologic molecules comprise about 5 percent of blood volume.) The resistance component is largely a function of the elasticity of the "great" arterial vessels and their immediate branches. Thus, any disorder or disturbance that leads to increased blood volume, or increased resistance, or both (the most common situation); will cause hypertension. There are dozens of such causes, both direct and indirect. For example, obesity leads to chemical and hormonal changes that increase blood volume and the resistance of the great vessels. So does diabetes. So do other entities such as stress, insufficient sleep, many drugs (both prescription and over-the-counter), illicit drugs, smoking, high cholesterol, primary kidney or heart disease, and many others. So how does high blood pressure harm us? Excessive pressure with each heart beat literally pounds the walls of the great vessels and injures them. The mechanical stresses and subsequent inflammatory changes stiffen and narrow the vessel walls. The healing processes involving vessel wall injuries are not very good. (If they were, we might live on average to perhaps 120 years.) The injured vessels become atherosclerotic, narrow, and often blocked. Blood flow becomes compromised, so that all of the bodies organs and tissues suffer compromised blood supply. Remember: no blood, no oxygen, no life. The organs most immediately vulnerable to blood flow compromise from the hypertension-induced arterial vascular disease are the kidneys, heart, brain, and eyes. Kidney failure, heart failure, strokes, and vision loss occur. Heart failure also occurs, because the heart muscle fatigues from the extra work necessary to pump blood at higher pressure through the stiffer, more narrow, more resistant great vessels. It follows, therefore, that the medications we use to treat hypertension either lower the blood volume (e.g. diuretics), or lower the resistance, or perhaps-- as a some medicines do-- both. Almost all patients with hypertension require a combination of at least two or three medicines to obtain proper decrease of blood pressure. This has been a most simplistic explanation of the extremely complex subject of hypertension. Medical science has worked out many of the mechanisms and intricacies, but much remains unknown. What is clear from even this truncated discussion is that there is much that we can do to minimize the incidence and complications of hypertension. Better diet, exercise, sleep, and smoking cessation immediately come to mind-- all words to the wise, and all subjects for future discussions. A final point: If you do have hypertension, DO take the medicines your physician prescribes, and DO keep your followup appointments Medical science has made it quite clear that hypertension should receive aggressive evaluation and treatment. We all should take seriously our obligation to keep ourselves as healthy as possible. (EG)

(This piece appeared several years ago on the senior citizens resource website:

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