What Is Blood Pressure?
Blood pressure is the pressure of the blood in your arteries. Each time your heart beats, it squeezes more blood forward into your arteries. Because the arteries are already full of blood, when the heart pumps more blood into them it raises the pressure in them.
This is important because once the blood is in the arteries, it doesn’t get another “push” until it gets all the way back to the heart. This means that the only way the blood gets from the arteries into all of the small vessels which carry the blood through the body’s tissues is from that pressure pushing it forward.
It is exactly that pressure which pushes the blood through the body’s tissues and finally into the veins which drain the blood back to the heart, where it gets “pushed” again. If the heart were to stop beating, the pressure in the arteries would drop. Without that pressure there would be nothing to push the blood through all of the body’s organs and the blood would just stop flowing.
Regulating Blood Pressure
It is important that the blood pressure be strong enough to keep pushing the blood around the body. The blood pressure is initially generated by the pumping of the heart. However, there are many other factors which affect the blood pressure, and which contribute to the body’s own continuous blood pressure monitoring system.
For example, all of the arteries in the body are capable of dilating or contracting to a slightly larger or smaller size. If they contract to a smaller size they will squeeze the blood inside of them and this will raise the blood pressure. If they dilate to a larger size, this will lower the pressure. Also, by contracting or dilating different blood vessels, the body can regulate how much blood goes to different organs.
When you are running, the arteries going to your leg muscles dilate so that more blood can get to your leg muscles. When you are eating, the arteries going to your stomach dilate so that more blood will go there to help you digest your food. When you are finished eating, those arteries will contract again so that your body is not “wasting” blood flow by sending extra blood to areas where it is not needed.
There are certain disease states which cause the arteries in many body parts to dilate even though those parts of the body are not being used at that time. If enough areas have their arteries dilate at the same time, the overall blood pressure in the entire system can become dangerously lowered. Conversely, if most of the body’s arteries constrict too much then the overall blood pressure will be too high.
There are also various chemicals in the body which help regulate blood pressure. For example, if you have ever been suddenly frightened and felt that sudden adrenaline rush when your heart suddenly beats faster and you start breathing heavy, you were experiencing the effects of the chemical adrenaline in your body. In addition to causing your heart to beat faster, adrenaline also causes your arteries to constrict and therefore raises your blood pressure.
Hydration And Dehydration
Another thing that influences our blood pressure is the total amount of fluid in our bodies. If we become dehydrated, the total volume of the blood in our system decreases. We haven’t lost actual blood cells, but there is less water mixed in with the blood. In effect, our blood becomes a little bit thicker and the total volume decreases. This means it takes up less room in our blood vessels and this causes the blood pressure to drop.
Our bodies, which are performing continuous blood pressure monitoring all the time, can compensate for this by constricting all of the blood vessels a little bit. But if we become too dehydrated and we outstrip the capacity of our body to compensate, then our blood pressure will drop.
Normally, our bodies regulate our blood pressure close to 120/80 mmHg. This means that the pressure right after the heart beats is 120 millimeters of mercury. That is the top number in the blood pressure reading shown on a digital blood pressure monitor. We call that the systolic blood pressure. Right after each heart beat the pressure starts to fall.
We record the lowest the pressure gets right before the next heart beat as the bottom number in the blood pressure reading, in this case 80 millimeters of mercury. We call that the diastolic blood pressure. You might be more familiar with PSI as a measure of pressure – “pounds per square inch.” The units of millimeters of mercury, or mmHg, measure the same thing but in different units. It quite literally means the pressure needed to raise a column of mercury (like in the old mercury thermometers, or the old mercury column manual blood pressure machines) by that many millimeters.
Low Blood Pressure And High Blood Pressure
The blood pressure in our bodies needs to be high enough so that we get blood to all of our organs, most importantly the brain. Because the brain is quite literally our highest organ, if the blood pressure drops the brain will feel the effects first. That is why dizziness or fainting can be one of the symptoms of low blood pressure.
You might wonder then, why do our bodies not simply keep the pressure cranked up really high all the time? That way we’d have enough pressure to get all the blood we need to all our organs, and by keeping the blood pressure very high we’d also have a built in safety margin so that even if the blood pressure dropped a bit, it would never get too low. Indeed, this is a good question and our bodies do have their own blood pressure monitoring system.
However we must remember that all of the arterioles and capillaries, the tiny blood vessels that carry the blood through the body’s organs and tissues, are extremely thin-walled so that oxygen, carbon dioxide, and other nutrients can easily pass through the walls of the vessel to and from the tissues.
After all, that’s the point of the whole system in the first place – to deliver nutrients and oxygen to the tissues and to remove waste products; not simply to circulate the blood around the body at high pressure for no reason.
High Blood Pressure – “The Silent Killer”
Because those small arterioles and capillaries are so small and thin-walled, they are very delicate. And when they are exposed to high pressures for a long time they can become damaged. They can develop scar tissue, becoming thicker and impeding the ability to deliver nutrients and remove waste from the body’s organs. This can result in what we call “end-organ damage.” In other words, the “end organs” – the organs to which the blood is being circulated, become damaged from the pressure in the blood vessels being too high.
Many organs are susceptible to this kind of damage: lungs, heart, brain, kidneys, and eyes, to name just a few. High blood pressure for a long time can damage all of these organs. The problem is that when the blood pressure is too high most people cannot feel it. But the damage in the organs slowly continues to accumulate even though you might feel totally normal.
That is why the disease of high blood pressure, or hypertension, has been nicknamed “The Silent Killer” – because the damage builds up slowly, silently, without us even realizing that it is happening, until enough organs become damaged that in the end it can become fatal. But high blood pressure is not only dangerous due to chronic end-organ damage.
Sometimes the blood pressure can become so high all at once that a blood vessel somewhere in the body can actually tear open, causing internal bleeding. If this occurs in the brain, it causes a hemorrhagic stroke – a stroke due to bleeding. If it happens inside the abdomen it can cause a ruptured abdominal aortic aneurysm – a tear in the biggest artery in the abdomen which can cause massive internal bleeding. For all these reasons it is important to have your blood pressure checked regularly with a good blood pressure monitor.
Blood Pressure Monitoring
Traditionally, blood pressure has been monitored by using a manual blood pressure cuff placed on the upper arm and a stethoscope. There is a pressure gauge which measures the air pressure in the cuff. The cuff is inflated to a pressure higher than the blood pressure. Because the pressure in the cuff is higher than the blood pressure inside the arteries in the arm, the cuff will squeeze the arteries closed and no blood will flow through them. The pressure in the cuff is then slowly lowered while listening to the artery in the arm with a stethoscope. One can hear the sound of the blood starting to flow again and the pressure at which this occurs is the systolic pressure, the top number in the blood pressure reading.
The pressure in the cuff is lowered further until all sounds of turbulent flow from the compression of the artery by the cuff have stopped and the blood is flowing smoothly without any sounds. That pressure is the diastolic pressure, the lower number in the blood pressure reading.
Electronic Blood Pressure Monitors
Today there are electronic blood pressure cuffs which do the same thing but are able to automatically hear the changes in flow corresponding to the systolic and diastolic pressures. These automated blood pressure cuffs are used commonly in hospitals and doctors offices.
For those who wish to measure their blood pressure at home, one can purchase an automated home blood pressure monitor. A wrist blood pressure monitor is a similar device which compress the arteries in the forearm near the wrist rather than in the upper arm. These machines are smaller and can be easier to use.
The CardiacSense Medical Watch – A Cuffless Blood Pressure Monitor
Modern sensor technology has given us the ability to measure blood pressure electronically without compressing the artery with an inflatable cuff, by measuring the actual pulsations within the artery using a single sensor array. This means that the pressure can be measured faster and that the monitor itself can be much smaller. The convenience of being able to measure blood pressure so quickly and easily means that it can be measured more often to get a better sense of the average blood pressure throughout the day, or to determine what the blood pressure is at a specific time when a person might be feeling a particular symptom.
The CardiacSense Medical Watch functions as a blood pressure watch in addition to measuring many other medical parameters. Because it is a wearable blood pressure monitor, it can easily measure your blood pressure wherever you are, whenever you need it, without having to carry around an old-style bulky blood pressure checker.