KIIP CALM AND READ ON
Blood pressure is a medical term that represents the amount of mechanical pressure applied to blood tissue in order to cause it to flow. While increased blood pressure promotes better function on a temporary basis, chronic and abnormally high blood pressure causes wear and tear of blood vessels, and serves as a possible indicator of problems with heart (cardiac) function or the status of the Aorta.
Other health problems are correlated with abnormally high blood pressure as a pathology. Understanding blood pressure in depth begins with understanding the mechanical cycle of the heart. The mechanical cycle of the heart describes the changes to mechanical pressures during one cycle of cardiac work, or in other words, during one heart beat.
Advertisement
The mechanical cycle of the heart can be divided into two processes or stages. The first is known as the diastole phase and the second is known as the systolic phase. During the diastolic phase blood flows through the Left Atrium into the left ventricle, creating the volume of blood next to be pumped out of the ventricle and into the aorta. While the diastole phase is ongoing, the aortic valve between the left ventricle and the aortic artery is closed, yet the bicuspid valve between the left atrium and the left ventricle is open.
Towards the end of the diastole phase, the walls of the atrium contract and produce force aimed at pushing more blood into the ventricle before the bicuspid valve closes, preventing blood from entering the ventricle. From a functional standpoint the diastolic phase is dedicated to filling the ventricle up with blood, also termed "cardiac filling".
The volume of blood that fills the ventricle at the end of the diastolic phase is termed "end diastolic volume" or EDV. The greater EDV is, the more mechanical pressure is applied onto the ventricle's walls since fluids cannot be condensed, and now this blood volume has nowhere to go. As the bicuspid valve closes, the wall of the ventricle contract and produce force that pushed against the volume of blood within the ventricle causes the internal mechanical pressure to rise more and more as the ventricle continues to contract.
At some point, the internal mechanical pressure surpasses the pressure that the aortic valve can withstand, and the valve opens. The opening of the aortic valve creates an opportunity for blood to flow out of the ventricle and into the aorta, yet blood does flow out immediately. As the aortic valve opens, blood that is pushed by the ventricle into the aorta is met with aortic resistance to flow. Since arteries are elastic, they behave as "resistive blood vessels" that at first increase the resistance to flow in them. As the aorta's resistance to flow is applied against the ventricle, blood flow out of the ventricle is delayed for a split of second.
Once the ventricle pushes blood stronger than the aorta can resist, blood actually flows to the entire body as part of the systemic circuit. Accordingly, diastolic blood pressure (DBP, mmHg) is the mechanical pressure at which the aortic valve opens, while systolic blood pressure (SBP, mmHg) is the mechanical pressure required to overcome aortic resistance and allow blood to flow to the entire body. Pulse Pressure (PP, mmHg) is the mathematical difference between SBP and DBP.
Thus, PP = (SBP - DBP) and represents the amount of physiological work required for blood to be successfully pumped beyond the aorta. Pulse pressure represents how hard (physiologically) a person's heart must work in order to achieve the one functional goal of the heart - pumping out blood. We aspire to have lower pulse pressure as an indication of a more healthy and efficient heart, as well as a possible indication of the health of the aorta. The less aortic resistance, the easier the heart's work, and the faster blood flows to the entire body.
Blood pressure is presented by both the values of SBP and DBP, where the high value is a person's SBP, and the lower value is the DBP. Blood pressure of 120/80 mmHg is the average blood pressure in the population, that is not correlated through research with clinical problems. It is not the "perfect" blood pressure. The "perfect" blood pressure meets the following criteria:
Values are as low as possible (both SBP and DBP).
The person functions normally.
The low values do not represent hypotension due to a clinical problem.
Pulse pressure is as low as possible.
Advertisement
Increase blood pressure, increased aortic resistance, and increased pulse pressure, are all signs of either an existing cardiovascular disease or future cardiovascular disease (CVD). All three are indications that the heart is working harder than normal to pump out blood. If untreated for long, serious heart and blood vessel problems may result.
Comments