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Current time:0:00Total duration:11:25

Video transcript

let's imagine that I'm here this is me at the age I J I'll do this right now so let's say at the age of 31 and then I go into the future so this is a line for the present and then I go into the future and this is me again and this is now at the age of 71 so I've got 40 extra years I even picked up a cane to help me walk around and finally I go even further in the future I'm being very optimistic I'm going to go ahead and say this is at the age of a hundred and one I live to be a centennial I'm sitting in a wheelchair and I'm going to wave out at you so that's me in a wheelchair at the age of 101 and we're going to apply that formula we've been talking about so much Delta P equals Q times R so I said Q is cardiac output and we've got R is resistance so we've got this formula and let's say I go to the doctor's office and I go today and I go to 40 years and I go again when I'm a hundred and one and today they tell me my blood pressure is 120 over 80 and actually I went not too long ago and that's pretty much what they told me it was and I go in the future and in 40 years they tell me it's actually gone up my blood pressure is now 150 over 90 and in fact I go again when I'm 101 and they say it's 180 over let's say 105 so the blood pressure is rising and that's basically what I'm told and they say well you know you got to make sure you eat well and exercise and that should help your blood pressure and I'm left wondering what the connection is between the two so let's figure out what that connection is exactly so my blood pressure I just said is 120 over 80 and if I want to figure out my mean arterial pressure so my mean arterial pressure meaning the average pressure in my arteries I can actually use my blood pressure to give me a good guess as to what it's going to be so I know that I spend about 1/3 my mean arterial pressure is going to equal a sir earn times my systolic because I know I spend about a third of the time my heart does anyway sends a third of its time beating and it spends two-thirds of its time relaxing and the relaxing pressure is the diastolic pressure that's eighty and so that works out to about 95 and so that's how I came up with that 95 number and that's also why it's not exactly a hundred which is what you think an average would be between two numbers but it's because we don't spend the exact same amount of time in systole as diastole so then if I wanted to figure it out here it would be a 1/3 times 150 plus 2/3 times 90 and that works out to 110 and if I wanted to do it at the age of 101 my mean arterial pressure would be 1/3 times 180 plus 2/3 times 105 and that works out to 100 and let's see 60 and 70 30 130 so I figured out my mean arterial pressure and then I also let me write that was a line I also need my mean venous pressure because we know we're going to have to subtract the two from another one another to get the Delta P Delta meaning the difference so mean venous pressure right now is about five and let's assume this is one of a few assumptions we're going to make let's assume that it doesn't change and over a few years it really stays around the same it's about five well then if I know that my Delta P is easy to figure out right I can just take 95 minus five and that would get me 90 and I can take 110 minus five and that's 105 and I can take 130 minus five that's 125 so I figured out my Delta P which is basically my mean arterial pressure minus my mean venous pressure and that equals my Delta P okay so far so good now let me change colors to figure out my Q my flow and right now I have let's say a stroke volume and write it up here stroke volume meaning each time my heart beats about 70 milliliters of blood go out so each time my heart beats it sends out to the rest of the body 70 MLS of blood and that's based on the fact that I'm about 70 kilos and my heart rate is about 70 very relaxed heart rate and let's assume just as we did with the main main venous pressure that that doesn't change so this is not going to change over time so this works out to about five liters a minute because Q is simply like that here Q is simply s V times H R and so I'm just multiplying those two numbers together and get about five liters a minute and it doesn't change overtime so five liters a minute here five liters a minute here and I should probably mention all of my pressure units should be millimeters of mercury I didn't write that just to not clutter up the board but let's just assume that well it's not assuming it is millimeters of mercury so now using my equation I can now say well Delta P and actually maybe up here actually even change this to be blue so that I'm consistent so Delta P equals Q times R so if Delta P is ninety and Q is five my resistance equals on 18 right I mean it's just a bit of maths that I did very quickly but 18 times five is 90 and here I could figure it out 105 divided by five would give me a resistance of 21 and here I would figure out that it's going to be 25 so one thing that I've been told by my doctors my blood pressure is rising and two things that I've assumed are that my main venous pressure are the same you know my cardiac output is the same and if I assume that and that's definitely not true for everybody but if I assume that for me then that means that my resistance has gone up over time my resistance has gone up and let's let's now change screens and figure out how that could possibly happen so let me draw myself out again so I've got three versions of me have got the present me at the age of 31 I've got the future me with a cane at the age of 71 and I've got the really old version of myself living at a ripe old age of 101 waving in fact so three versions of myself and if I was to draw out my arterial tree let's say a simplified version of my arterial tree let's say here's a vessel coming through and I've got let's say another vessel and this branch is here and I've got a third vessel and this branch is here right now my arterial tree looks pretty good pretty clean and that's why my resistance was 18 you know blood is flowing through very smoothly it's going out this way to feed the kidney and maybe my ears and my eyes and my foot and it's basically making its way through no trouble now at the age of 71 something happens I feel me just draw a little divider line at the age of 71 something happens I have let's say the same arterial tree I try to draw it the same way except now I've been eating for 40 years you know foods that are not the best and I certainly have an exercise a whole heck of a lot I haven't gone to the gym very often and now I've got buildup of plaque so let's say I've got a plaque right there and I've got a plaque let's say another one right there and let's say I have a plaque right there so I've got three little plaques and we'll get into plaque and what what it's made of exactly in a future video but for the moment just think of it as something that's blocking up that vessel and it's usually made of fatty substances and macrophages and cells that have died and all sorts of kind of basically crud that fills up the vessels and so because it's filled up the vessels now here my radius got smaller my vessel radius and here got smaller and over here it got smaller so blood is it's flowing through is having a tougher time getting through because the radius is smaller in these spots and as you know if you calculate total resistance and that's what actually this is total resistance the total resistance will start to slowly climb up and in this case maybe it climbs up to 21 and now years go by let's say 30 more years go by I'm now in a wheelchair and I continue continue to not eat so well I know the same sort of fast food that isn't healthy for me but I can't possibly stop because I find it tasty and at the end of the day my vessels look like this I have that same one as before let's say and let's say this one actually grew longer so instead of just being part of the vessel that's it's huge now this one got very big and let's say this one up here actually continued to grew a little bit as well but I also picked up another one right here let's say and I also got one right here so I have a few more blocks in the road and so now my blood is having a real hard time getting through because it's got more obstruction to flow all my all my pads have a smaller radius and we know it I've I've mentioned a number of times now about the relationship between a radius and resistance net as the radius everywhere gets smaller the resistance is going to get bigger and so my total resistance here that see is about 25 so now you can see how eating certain way and not exercising is going to lead to potentially developing these plaques that act as roadblocks and get in the way of blood flow and the reason that that's a problem is that as we see now the radius gets smaller the resistance goes up and in the previous slide here we actually can see now that as a resistance goes up assuming that the other things kind of stay the same your blood pressure can go up and so when you hear in the doctor's office that you have a blood pressure of a certain number over number that's one thing that we can measure and what it tells you is a little bit of information about some of the things that we can't easily measure such as resistance so let's stop there and we'll pick up