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Current time:0:00Total duration:9:57

Video transcript

all right so you take a little balloon let's assume you see it on the table and you can't resist yourself you take that balloon and you start to to think about how to do a little experiment with it maybe that's not what you're thinking that's certainly what what you should be thinking because we're going to have a lot of fun checking out learning about this balloon by giving it some air so imagine if you put some pressure into that balloon what would happen it would of course get larger right so you know that the volume of the balloon is going to go up as you put pressure into that balloon but you actually want to measure it let's say so you go ahead and give a small amount of pressure may be a small breaths and this balloon gets a little bit bigger and you note that it's let's say a small amount of pressure is over there and it gets a little bit bigger over there so you put a little X right there very good now you go back and give it a little bit more pressure a little bit bigger breaths and you do the same thing you say well there's my pressure and now it's a little bit bigger so I am going to put a little X right there and you do this again with a large large amount of pressure and you notice the balloon is getting much bigger so you figure out that as you put in more pressure the balloon is getting bigger and on top of that it's happening at a linear rate right so the more pressure you're putting in you're getting a direct amount of volume for that now not all balloons are going to behave this way but let's let's assume for the moment that this balloon does that so it gets bigger and bigger as you put in more pressure great this is my balloon now you notice that there's one more thing sitting on the table and you grab it and it's a plastic wand like this and you dip it in soap and you make a balloon or a bubble rounded not a balloon this time a bubble out of the soap so you give it a soft breath just like you did before and you notice that even with a soft breath you get a large volume so that's interesting right so kind of a large volume and then you give it a medium-sized breath a medium-sized breath and you get even a larger volume let's say something like this even a larger volume and you can kind of see where this is going to go because I'm going to give it a large breath and maybe it'll you know fill out this entire corner something like that you get this enormous bubble and it doesn't burst let's assume so now you have three little blue X's for the bubble and you connect them just as you did before and this is my bubble line and you can already see something kind of interesting right you can see that the balloon has a smaller slope than the bubble the bubble is is rising more quickly and so thinking about this you can actually say well this is let's say a formula for the soap rise in volume over run which would be pressured in this case and if you do rise over run you get the slope and in this case we're going to call the slope compliance compliance really interesting and important word seems pretty simple right and it's just how big does something yet when you give this or amount of pressure and you can see in this case that the bubble has more compliance than the balloon okay so now we've figured out a couple things and I'm going to add one more new word which is actually just the inverse so let's what if I flipped it around what if I put pressure over here and volume over here I can do that right I can just take the same data the same information and just flip the two axes around and if I did that then in this case the balloon line would be over here something like that right because all I'm doing is just flipping the way we look at this chart and the bubble line would be over here something like that so now my bubble and my balloon have switched places because the axes have switched I mean in a way you could literally just tilt the graph over you get the same things there's nothing magical but the thing that is different about this is that now if I'm calculating rise over run or the slope I actually have flipped the volume pressure right so now I pressure is on top and the volume is down below and if you have it like this pressure over volume we actually call that elastance so the first one we called compliance in this one we call elastance and so you can see that elastance and compliance are basically just inverses of one another they're just the flip of one another and so these two words you're going to hear them but I want you to see how they're very very much the same kind of thing is just that one is the inverse of the other one okay so now we've gotten that I'm going to make some space here like that and I'm going to bring up one final point and that might be this what if you have an artery so instead of balloons and bubbles let's talk about blood vessels for just a second what if you had an artery like that and here's my artery and you decide that you want to lock it off on one end maybe with your hand like this and here's your hand blocking it off and let's say you do the exact same thing with a vein you decide you want to make a vein and lock it off on one end I'm trying to draw these two to be the same size so if they look different than please assume for the moment that they're the same size same length block it off so that end is blocked off with your hand and nothing can leak out right so you only have one to open in and now let's zoom that you cover up this end let's say you cover it up and you have just one tiny opening here you cover up the and you do the same thing you have one tiny opening here and this opening it's how we go down so it looks the same this opening is to a bicycle pump I know this is sounding very strange why in the world would you have a bicycle pump attached to an artery or a vein or you'll see in just a second here's my bicycle pump and I'm going to actually pump up my artery and pump up my vein much the same way that I did before with the balloon of the bubble and you're going to start seeing some really interesting parallels I think so let's say I pump up the artery immediately what happens well if I put a certain amount of pressure in there let's say I put the large amount of pressure that I'd put in the balloon I'm going to get something like this where this artery is going to start swelling up and this goes away so now my artery looks a little fat like a plump little sausage and if I give that same amount of large pressure to the vein it's going to do something like this it's going to get in norman's and I have to erase these little lines to make it clear that my vein is getting huge so with a little bit of pressure the artery gets a little bit bigger but the vein gets a lot bigger so with the same amount of pressure you see a difference in the volume and this is actually a critical point right because the artery in the vein are really they're behaving just like the balloon in the bubble and it's actually very very similar so if I was to make a volume pressure loop with this I could actually erase the word balloon to bubble and really replace them completely with artery and vein I could just write the words artery in vein and essentially they would be behaving this way artery up here artery over here then vein in the other two spots so you can now see that the artery has lower compliance than a vein and higher elastance than of eight and now just speaking to the compliance issue imagine that you've had a really rigid iron pipe something completely solid it's not going to budge no matter what you do well for that solid pipe you'd actually get something like this you would have even less compliance so if you're ever thinking about the issue of complaints and we talked about stiffness think about these curves and the fact that where the slope is tells you how complained something is and that arteries are going to be more compliant than a stiff pipe certainly the less compliant than the veins