We defined our 4 lung volumes as non-overlapping measures of lung space, but sometimes it makes more intuitive sense to talk about more than one volume at a time. To do this, we have 4 lung capacities. So our lung capacities, we're going to define as measures of multiple lung volumes added together. Now, to see why we want to do this and to see how it works, it makes sense to just go through these lung capacities. So, we're going to start here at our first one, our inspiratory capacity. Our inspiratory capacity, we're going to define as just after a normal exhale, breathing out normally, how big is your biggest inhale? Right? So, you breathe out normally, and then, how much air can you breathe in after that normal exhale? Well, we can see on our graph here, this is made up of 2 volumes. In pink, there's the tidal volume, and then in blue above that is your inspiratory reserve volume. Your tidal volume, just that normal in and out during quiet breathing, and that inspiratory reserve volume, how much more can you breathe in if you wanted to. So together, that's your inspiratory capacity. Well, we can highlight this on the graph here, inspiratory capacity. For an average-sized female, that's about 2400 milliliters. Average size male, about 3600 milliliters. So in that two and a half to three and a half liter range for most folks. But, again, this varies more than anything, just on body size. Alright. So, we'll leave that up there, their inspiratory capacity.

The next one that we're going to go through here is your functional residual capacity. So remember, your residual capacity is how much air is left in your lungs after you breathe everything out. How much air can you not get out of your lungs? And that on this graph was this brown part. But remember, normally, you're not breathing everything out of your lungs. Normally, you just sort of breathe out through your tidal volume. So your functional residual capacity is after that normal exhale, how much air is still in your lungs. And we can see on this graph here, it's going to be made up of 2 volumes. Well, we have our residual volume, but we also have the expiratory reserve volume. Expiratory reserve volume, the amount that you could breathe out if you wanted to, but you normally don't. Your residual volume, the amount that you just cannot get out of your lungs. Alright. So, we'll highlight this on the graph here. For an average-sized female, that's around 1800 milliliters. For an average-sized male, about 2400 milliliters. So in that two to two and a half liter range, again, varying more than anything, just based on body size. Alright. So, that's your functional residual capacity or your FRC. We will leave that on the graph there, highlighting that area.

But next, we're going to go into one called the vital capacity. And the vital capacity, to me, is sort of the most intuitive if you just want to think, like, how do I measure how healthy my lungs are? I think of vital capacity. Vital capacity here, it says after your biggest inhale, how big is your biggest exhale? Alright. So, you breathe in as hard as you can, then you just breathe everything out, all the air. So, just another way to think of it: how much air can I move if I try as hard as I can? What is my biggest biggest breath? Alright. So here, we can see that covered 3 different volumes. Right? We have going top to bottom, we have the inspiratory reserve volume in blue, the tidal volume in pink, and the expiratory reserve volume in the light blue there, so we can highlight this whole section on the graph there. That's your vital capacity. Alright. For your average size female, that's about 3100 milliliters. Average size male, about 4800 milliliters. So somewhere into like that three to five liter range, which when I start seeing those, you know, multiple liters, that just seems like a lot of air that you can move if you really want to. It's always surprising to me. Alright. Vital capacity.

Well, we got one more volume on here, I'm sorry, one more capacity on here, and this is the big one, your total lung capacity. Total lung capacity, it's just what it sounds like. How much total air can you fit in your lungs? So we're going to take all our volumes and we are going to add them together. Inspiratory reserve volume, plus your tidal volume, plus your expiratory reserve volume, plus your residual volume. So how much air can you possibly fit in your lungs? It's just this entire graph here. And here again, for your average size female, we have about 4200 milliliters. Your average size male, about 6000 milliliters, or 6 liters of air. Now I am an average-sized male, so that means that I should be able to fit in my lungs 3 of these 2-liter soda bottles worth of air. Again, this is one of these volumes that when you look at it, to me, that just seems like a lot of air that I could possibly fit in my chest, but that's the number. Alright. The last thing that we want to talk about here is called anatomical dead space, and that's just this idea as we've been talking about all these volumes and capacities, we're talking about how much air moves in and out of the lungs, how much air moves in and out of the alveoli. But there is a volume of air that remains in the airway during ventilation. So, think about your airway, your bronchi, your trachea, your upper respiratory tract. That altogether is about 150 milliliters. So when you exhale, the air leaving, well, that last 150 milliliters of air doesn't actually make it out of your nose. Right? It leaves the alveoli, but it only makes it as far as the bronchial, the trachea, or the upper respiratory tract somewhere. And then when you breathe in again, when you inspire, well, that first 150 milliliters of air, where is it coming from? It's coming from your respiratory tract. So in any one of these volumes, any one of these capacities, when you're talking about moving air in and out of the lungs, 150 milliliters of air, well, if it's for breathing in, the first 150 milliliters of air is coming from your respiratory tract. If it's breathing out, the last 150 milliliters of air actually never makes it fully outside of the body. It stays in the respiratory tract. Okay. That's your anatomical dead space. We've now talked about 4 different volumes, 4 capacities, anatomical dead space, a lot of terms. We're going to do some practice problems, some examples to keep them straight. Give them a try, and I will see you there.