Blood Pressure - Basics

in this video we're going to take a quick look at blood pressure now blood pressure is the pressure or the force that the blood in your vessels exerts on the walls of that vessel okay now how do we generate this sort of pressure well today we're going to have a look just at the left-hand side of the heart because the left-hand side of the heart deals with oxygenated blood that it needs to deliver to the whole body you know that when that left ventricle contracts pushes blood up into the aorta and the aorta branches numerous times and ultimately leads to capillary beds of the tissues for the tissue to get fed now without the right amount of pressure behind the blood pushing it through the blood will not get to the tissues and perfuse at the sites in which it needs to meaning it won't be able to feed those tissues so blood pressure is required for perfusion in order for the blood to feed the tissues at the appropriate sites and you know that that left ventricle when it contracts needs to send the blood to the top of your head to the tip of your toes so there needs to be a relatively high amount of pressure being generated from that left side of the heart the reason why we're not talking about the right-hand side of the heart today is because when that contracts it's just sending the blood to the lungs now yes that's important but the lungs are not very far away from the heart other so when the right-hand side of the heart contracts it does not generate a huge amount of pressure in order to get the blood to the lungs we want to talk about what we call the systemic blood pressure and the systemic blood pressure is generated by the left hand side of the heart specifically the left ventricle so what I've drawn up here is the left hand side of the heart so I've got the left atrium and look at the left ventricle and you know that the left ventricle leads to the aorta and then the aorta is going to branch numerous times and that's going to branch again into arterioles okay so I want you to remember that this is left hand side of the heart left atrium left ventricle Ayana and all these branches and these are arterioles ultimately go into capillary beds okay now when the blood from the pulmonary vein fills that left ventricle it's now oxygenated because pulmonary vein means from heart from lungs so this is oxygenated blood coming from the lungs going into the left atrium contracts pushes blood through the bicuspid or mitral valve into the left ventricle and you know that the walls the muscular walls of the left ventricle are extremely muscular okay so when this muscle contracts it squeezes and pushes blood up through the aortic semilunar valve into the aorta now important point when the left ventricle contracts this is known as systole okay so contraction is referring to systole when this left ventricle relaxes that's called diastole so contraction systole relaxation diastole let's write that down systole is contraction diastole relaxation all right so you must keep that in mind now Bloods filled that left ventricle now that left ventricle contracts so that systole and what happens when that left ventricle contracts as that left ventricle contracts the blood gets pushed up through the pulmonary semilunar valve and goes into the aorta now when it contracts it produces a certain amount of pressure and I told you that pressure is the force of the blood on the walls of the vessels this pressure that's generated in this left ventricle under systole under contraction is 120 millimeters of mercury okay now this pressure gets transmitted into the old so the 120 millimeters of mercury gets transmitted into the aorta and because the aorta is very stretchy they oughta start to bulge out so what you can see is this left ventricle contracts systole creates a pressure inside that left ventricle of 120 millimeters of mercury that blood with a pressure behind it of 120 millimeters of mercury is pushed into the very distensible very stretchy a order and 120 millimeters mercury stretches the a on our out okay that is what we call the systolic blood pressure and therefore it's 120 millimeters of mercury okay now when that left ventricle relaxes when that left ventricle relaxes the pressure inside this left ventricle drops and that means these valves closed because the blood that's here in the aorta whoa once they come back down there's no more pressure behind it so the blood that's pulled here wants to come back down but luckily the aortic semilunar valves closed now the other thing is this because that i aughtta was stretched out under systole just like a rubber band would be when this ventricle relaxes this rubber band recoils and comes back in now as this rubber band recoils and comes back in what do you think happens to the blood that's pulled here it gets pushed forward okay now because even though the left ventricle is relaxed it means that because of the stretch ability of the aorta that the blood could continually be pushed through so basically if contraction blood comes out descends that pressure on the wall is 120 millimeters of mercury then when the vegetable relaxes the aorta comes back in it recalls back in and continues to propagate blood through this pressure that's propagated from the recoil of the aorta is the distilling pressure and so the distilling pressure is about 80 millimeters of mercury okay the distilling pressure is about 80 millimeters of mercury now hopefully that makes so that's why when you measure your blood pressure so remember the aorta branches off one of the branches is the brachiocephalic branch okay and the brachiocephalic branch is going to come down into the subclavian and the subclavian is going to come down into the brachial and you're going to have your brachial artery and what do you do you measure blood pressure from the brachial artery whatever pressure is in that brachial artery is reflecting the pressure of the aorta and what that aorta has generated okay and when you do this I want you to think about when you measure do manual blood pressure readings you have that cuff and you wrap the cuff around the patient's arm and you pump that cuff up you put pressure in the cuff because if you have your brachial artery with blood moving through you know that Bloods moving through in a fashion like this contract up Bloods being pushed through a understands left ventricle relaxes recoils continues to push blood through that's why blood doesn't squirt through your arteries like this blood is consistent push their own assistant Lee continues to push diastole so push through when it contracts continuously it pushed her under relaxation okay 121 its contracted 80 millimeters of mercury and it's relaxed now if we have a look at this blood vessel you're going to have pressure being placed upon the walls of this blood vessel the brachial artery and you're going to wrap a cuff around and pop it up now when you pop that cuff up what's it feel it feels like it's getting tight up on your arm and that means that the cuff starts to if we had this cuff wrapped around the vessel as you pump up the pressure it starts to push on the artery now remember what's the outward force on this artery well under systole it's 120 millimeters of mercury so under systole of 120 millimeters of mercury pushing out on this vessel so what do we need to do in order to close this vessel up if we wanted to close this by some blocking all the way up we need to put equal to more pressure in the opposite direction that makes sense 120 millimeters of mercury pushing out we need to put on June 21 millimeters of mercury pushing in and that's what we do we pump the cuff up to about 160 170 millimeters of mercury just to make sure and that means that it's fully occluded the pressure going in is beating the pressure coming out and what do you do you take the stethoscope and you put on the brachial artery and you listen and what you hear is nothing when it's fully occluded fully blocked okay but then what do you do you slowly release the pressure of the cuff and the cuff starts to come out and out and out and out now as soon as the cuff has come out enough that a little bit of blood can squirt through what does that mean if the cuff has come out enough that a little bit of blood can squirt through that means that the pressure inside the vessel is just overcoming the pressure of the cuff which means I know contraction on assistant Li there's a certain amount of pressure coming through and it's overcoming the cuff now that's your systolic reading so when you have your stethoscope on this thing as you releasing the pressure you'll hear o j-- sound and that is going to be your systolic value look at the reading the reader on the swing momen ometer you have a look at the reading and that's giving you systolic value then you continue to release the pressure and you'll keep hearing these sounds until the sound is stopped when the sounds stopped it means the vessel is fully open and there's a constant flow of blood through as soon as you stop hearing that sound that's your diastolic value its meaning that this little smallest amount of pressure being generated in this vessel is even able to get passed okay that's measuring your manual blood pressure now last thing I want to talk about is when we look at blood pressure you need to think of the calculations that go towards it now I told you that 120 over 80 is the normal blood pressure whatever that may mean but I want to talk about what things can alter blood pressure okay now I'm going to do another video on the things that can alter blood pressure but I just want to introduce in the last 1 minute of this video this very important little equation which is blood pressure is equal to cardiac output times systemic vascular resistance what does this mean it means the blood pressure the pressure that the blood is exerting on the walls of your artery is equivalent to cardiac output this is the amount of blood being pushed out of your left ventricle over time how much blood has been pushed out of your left ventricle over time blood quantity basically volume systemic vascular resistance well this is the systemic blood supply here and it's referred to vascular meaning blood vessel resistance so how much resistance are these blood vessels putting on the blood behind it now this is important because your arterioles have smooth muscle wrapped around them and this smooth smooth muscle can either constrict or dilate if this smooth muscle constricts what do you think happens the blood pulls backwards and the blood pressure increases if they dilate more blood can be pushed through in the blood pressure on the walls back here are less okay so the amount of blood coming out of the heart multiplied by the amount of resistance being experienced distal to the arteries can regulate blood pressure in the next video I'm going to talk about this in detail because all the antihypertensive drugs that we give our patients well on an altar carry out output or it will alter systemic vascular resistance I hope that made sense

Channel: Dr Matt & Dr Mike

Views: 42,683

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Id: keYtWNAJY64

Length: 13min 27sec (807 seconds)

Published: Tue Aug 09 2016