Lung Volumes and Capacities - Online Tutor, Practice Problems & Exam Prep

Lung volumes and capacities are essential for understanding pulmonary function. Tidal volume (TV) is the air exchanged during normal breathing, averaging 500 mL. Inspiratory reserve volume (IRV) allows for deeper inhalation, while expiratory reserve volume (ERV) enables forceful exhalation. Residual volume (RV) remains in the lungs post-exhalation. Capacities like inspiratory capacity (IC) and vital capacity (VC) combine these volumes, with total lung capacity (TLC) representing the maximum air volume in the lungs. Anatomical dead space refers to air in the respiratory tract that doesn't reach alveoli, approximately 150 mL.

Lung Volumes

We've been talking about ventilation, the movement of air in and out of the lungs. But you may just be wondering, how much air are we talking about? How much air actually goes in and out with each breath? We're gonna talk about that now, and there's actually two ways to talk about it. There's the lung volumes and the lung capacities. We're gonna deal with the lung volumes in this video, and lung capacities, we'll deal with in a future video. Now for both the lung volumes and capacities, we're gonna go through definitions that you should probably know, but then we're also gonna go through some specific values. Whether or not you need to know those values, like anything, it's gonna be up to your professor and your course, but I do recommend that you at least just understand relatively how much air we're talking about and how these different volumes relate to each other. Alright. So with that in mind, let's dive in. The lung volumes, we're gonna say, are non-overlapping measures of lung space. By non-overlapping, I mean there's gonna be 4 lung volumes. And if you take those volumes and the values for them and add them together, that should equal the total amount of air that you could ever possibly fit into your lungs. Alright. So let's look at these volumes.

The first one is going to be tidal volume. Tidal volume or TV. For each one of these volumes and capacities, we're gonna have a 2 or 3 letter abbreviation that we can use. So the tidal volume or the TV, this is the amount of air moved during quiet breathing or eupnea. That just sort of means remember, restful breathing when you're not really thinking about breathing. Now for both males and females, that's going to be about 500 milliliters. Alright. We're gonna graph all this out. We're gonna graph it for an average-sized male. So on this y-axis, it goes from 0 all the way up to 6,000 milliliters or 6 liters. Now for your tidal volume, we're talking about 500 milliliters. Graph it in here, in and out, in and out, in. Right? So that is the tidal volume, just that eupnea, that in and out restful breathing, 500 milliliters of air. TV right there. Alright. How much is 500 milliliters? Well, it's the size of this soda bottle. Alright. So this soda bottle here, 500 milliliters, a bit smaller than the one you typically get, like, at a gas station. But if like me, you bought a 6 pack of soda at the grocery store, they often come in 500 milliliter bottles. So during eupnea, this is the amount of air split between both lungs that goes in and out of those alveoli.

Now I'll be honest, when I look at that, it doesn't really seem like that much to me, but that's what it is. Alright. So we had the tidal volume, but, of course, you can take deeper breaths than that. And you can breathe in deeper, and you can breathe out harder. And so that gives us our reserve volumes. The reserve volumes, well that's air that can be ventilated beyond the tidal volume. So of course, you can sort of breathe in deeper, and that's going to be your inspiratory reserve volume. Your inspiratory reserve volume or your IRV. That's well, imagine you've just finished your sort of normal tidal volume inspiration. Now you take your maximum forced inhalation, the deepest breath that you can take, And so that additional amount of air that you can bring in is gonna be about 1900 milliliters for your average-sized female to about 3100 milliliters for your average-sized male. But just know all of these volumes really vary more than anything just on body size. Alright. So on our graph down here, right, this person has just breathed in as part of their tidal volumes. You breathe in normally, and then how much more air can you possibly get in the lungs? That is that IRV. We said there, right, 1900 to 3100, that's, like, 2 to 3 liters of air. So when we're thinking in soda bottles. Right? So for your average-sized female, another 2 liters of air is going to go in the lungs. Average-sized male, 3 liters. Now I am an average-sized male, and I have measured my inspiratory reserve volume before, and it's right around 3 liters. So when I take that deep breath after my sort of normal inhale, this is how much air is going in my lungs. Again, split between both lungs. But when I look at that, I sort of wonder where it all goes. Right? That to me seems like a ton of air to be able to get in there. But, again, I've measured it.

Well, we're looking at this graph here. And in the graph, that person has full lungs. They breathe out normally just through relaxation. The air goes out. Now they're at the bottom of the tidal volume. But, of course, you can breathe out harder than that. And that is going to be, excuse me, that's gonna be that expiratory reserve volume or the ERV. That expiratory reserve volume or ERV, that's forced exhalation. How much more air can you get out after your normal exhale? And it's gonna be between 700 to 1200 milliliters, again, for your average-sized female and male. So on our graph here, you breathe out normally, then how much more air can you get out? That is that ERV, and we're saying that that is somewhere in the range of 700 to 1200. So we're talking another liter of air that you can get out if you want to. Alright. So that's the expiratory reserve volume, but we can look on this graph here. There the person finishes breathing. They breathe in normally, and they're back to their tidal volume. Anyways, so we finish the graph there, but we'll notice that there's this empty space at the bottom of the graph. There's over 1000 milliliters of air down there, that we didn't get to when we're breathing in and out. That is the residual volume. The residual volume or the RV. The residual volume, you can think of it about as the amount of air that resides in your lungs even after you've forced as much air as you can possibly get out. Is the amount of air that cannot be exhaled from the lungs, and it's between somewhere like 1100 to 1200 milliliters. So on this graph down here, this is our RV and, well, it's again a little bit more than a liter of air. Remember, that's important because if we did breathe all of that out, well, all our alveoli, our lungs would collapse, and we don't want that. Alright. Those are the lung volumes. I understand that getting these straight in your head can take a little practice. We'll do that next, and then we will look at the lung capacities.

Lung Volumes and Capacities Example 1

Alright. For this example, it says, in the table below, descriptions of the 4 lung volumes are given. The graph shows spirometry results for a typical healthy female for reference. Fill in the empty cells in the table according to the following instructions.

So it says here. Write the name or abbreviation of the lung volume to which each description refers. Then rank the volumes in order of size from 1 to 4, 1 being the smallest and 4 being the largest. So, quickly, just for reference, behind my head here, we have this graph of those results showing the volume for, again, what we said was a typical healthy female.

Now, remember, this varies more than anything just based on body size. So let's go through some of these descriptions. Our first one here says, the amount able to be inhaled beyond normal inspiration.

Do you remember the name of that volume? Well, I'm going to look over at this graph here first. Remember, as we breathe in normally and then how much more can we breathe in, that's represented by that part of the line there. That's that blue section of this box here, and that we call the Inspiratory Reserve Volume. Put the v for volume there, and if you want the abbreviation, it's just the IRV.

Let's go through all these before we try to rank them in terms of size. Next, we have the amount left that cannot be removed from the lungs through expiration.

So, do you remember what that is called? Well, again, as we look at our graph here, that's the amount that, after you exhale as hard as you can, how much air is still left in your lungs. And so in our graph, that's this bottom beige section, and that is your Residual Volume or the RV, if you're using the abbreviation.

The next one here, it says the amount of air moved during quiet breathing. Do you remember that one? Well, the amount of air moving in and out during quiet breathing in our graph here, that's this pink section of this graph, and we call that your Tidal Volume or your TV for short.

And then finally, we have the amount able to be exhaled beyond normal expiration. Remember what that is.

So, in our graph here, we exhale normally, and then it, sort of, this part of the graph right there, how much more can you breathe out if you're trying to? So this sort of light-blue gray section there, and that was the Expiratory Reserve Volume. I'll just write the v there.

So now we just need to rank the sizes from 1 to 4 with 1 being the smallest. So, this is pretty easy, actually, with this graph here if you know what each one represents. So which one is the smallest? We'll start there with the one. Well, the Tidal Volume, as I see that there in pink, that's the smallest one.

Tidal Volume gets my one, and I'll just put here that we said is 500 milliliters.

What gets the 2? Well, the next biggest thing on here is this gray section of the light blue-gray section of that graph there, and that represented the Expiratory Reserve Volume. So I'm going to put a 2 there, and we said for that average size female, that was about 700 milliliters.

Next. What's the next biggest? Well, as I look at the graph, the next biggest thing here is this beige section. That beige section was the Residual Volume.

Residual Volume gets the 3, and we said that for an average size female was about 1100 milliliters. Again, the question doesn't ask for the volumes, but I'm just giving them there as a reminder. And then finally, we have the Inspiratory Reserve Volume. The last one we need to know there, and that is this biggest blue section on the top.

So that gets our 4. That's the biggest, and that, for an average-sized female, is going to be about 1900 milliliters.

There you go. Those are your lung volumes. We'll practice naming these some more and more practice problems. I'll see you there.

Of the following four lung volumes, which do you think would be the hardest to measure without advanced instrumentation?

• A. Expiratory reserve volume (ERV).
• B. Tidal Volume (TV).
• C. Residual Volume (RV).
• D. Inspiratory Reserve Volume (IRV).

Under normal conditions which of the following volumes do you expect to be the smallest?

• A. Expiratory reserve volume (ERV).
• B. Tidal Volume (TV).
• C. Residual Volume (RV).
• D. Inspiratory Reserve Volume (IRV).

Lung Capacities

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.

Lung Volumes and Capacities Example 2

For this example, we're going to compare someone with normal healthy lungs to someone who has COPD. There's a lot to read here though, so let's get going. It says below are 2 graphs showing lung volumes. One graph shows a healthy person while the other shows a person with COPD or chronic obstructive pulmonary disease. In COPD, many of the alveoli walls break down, creating relatively large open spaces in the lung with relatively low surface area. The lungs also lose elasticity and therefore do not recoil normally. On the line above each graph, identify each individual as either normal or COPD based on your understanding of lung volumes and capacities. Then, based on the graphs, write increased, decreased, or no change next to the 4 lung capacities listed, based on how you think they would be affected by COPD. Alright. So, first thing we need to do is look at these two graphs, and we have to identify one as normal and one as COPD. Now we see that they're broken up how we learned before. Let's quickly remind ourselves what the 4 lung volumes that we're looking at here are. Well, in beige, remember, that's your residual volume. In this light blue, we have your expiratory reserve volume. In pink, we have the tidal volume. And in this sort of darker blue, we have that inspiratory reserve volume. Now, for both these graphs, what's not labeled is the y-axis, but the y-axis in both of these is going to be the volume of air. Look at which one looks like the graphs we've been analyzing and which one looks a little funny. This one on the left looks normal. This looks like the graphs we've been analyzing. While this one on the right here looks a little out of whack, so I'm pretty sure this one is going to be the COPD graph. Now knowing that, we can analyze our 4 lung capacities here. So let's go through them one by one.

Total lung capacity. Well, first up, do you remember what volumes add up to make total lung capacity? It's just how much air you can possibly fit in the lung. So, it's really just how tall these y-axes are. So for COPD, does that look increased or decreased? That one should be pretty straightforward, right? It looks increased. And it's because many of the alveoli walls break down creating relatively large open spaces. So, someone with COPD just has less tissue in their lungs. Remember, that lung capacity is really just defined by how big your chest is. Well, if you have less tissue in there, you can fit more air. COPD generally increases total lung capacity.

Next, we have vital capacity. Do you remember what volumes make up vital capacity? It's your expiratory reserve volume, your tidal volume, and your inspiratory reserve volume all added together. So it's basically all this area in the blue and pink in both graphs. So, when you look at that for someone with COPD, is that increased or decreased? To me, that looks decreased. And that makes sense. Vital capacity is a sort of quick shorthand of how healthy your lungs are. How much is the biggest breath you can take? How much air can you move? Well, someone with COPD can move less air. We just see here that the area where the sort of breathing is occurring is smaller.

Next, we go to inspiratory capacity. Do you remember what volumes make up inspiratory capacity? It's your tidal volume and your inspiratory reserve volume added together, basically on these graphs from the pink up to the top. So, comparing normal and COPD, which one looks bigger? For COPD, it looks decreased. And again, that makes sense. If you have COPD, it's harder to breathe air in, and we can look at why. The lungs lose elasticity. Remember, breathing out, expiring, is relaxation and relies on the lung's elasticity to sort of squeeze downwards. Well, if they don't get smaller, if you don't breathe out as much air during your normal restful breathing, then you can't breathe as much in. So, having less elasticity means that it's harder to breathe more air in because your lungs haven't sort of gone down to a smaller size before you breathe in again.

Our final one here, functional residual capacity. Do you remember what volumes add up to make that up? It was your residual volume and your expiratory reserve volume. So basically from the pink down on these two graphs, you can compare that area and see right away which one is bigger. For COPD, that is increased by a lot. And it's increased really because of this residual volume. Remember the residual volume, that's the amount of air that you just can't get out of your lungs even if you want to. So someone with COPD, they have a lot of air in their lungs, but they can't move a lot of that air. A lot of that air is just sitting down there, stale, old air, not getting refreshed. And that's one major reason you do not want COPD. We have more practice problems to follow. Give them a try.

Which of the following would best predict how likely someone is to blow out all their birthday candles in a single breath?

• A. Tidal Volume (TV).
• B. Inspiratory Capacity (IC).
• C. Expiratory Reserve Volume (ERV).
• D. Vital Capacity (VC).

The Functional Residual Capacity can be thought of as a combination of which other measures of lung volume?

• A. Tidal Volume (TV) and Inspiratory Capacity (IC).
• B. Residual Volume (RV) and Expiratory Reserve Volume (ERV).
• C. Tidal volume (TV) and Functional Residual Capacity (FRC).
• D. Total Lung Capacity (TLC) and Residual Volume (RV).

Distinguish between inspiratory reserve volume (IRV) and inspiratory capacity (IC)?

• A. IRV measures total inspiration starting at the end of a normal expiration while IC measures total inspiration starting at the end of a normal inspiration.
• B. IC includes tidal volume (TV) and IRV; IRV does not include TV.
• C. IC includes both tidal volume (TV) and vital capacity (VC); IRV does not include VC.
• D. IC measures total inspiration starting at the end of forced expiration, while IRV measures total inspiration starting at the peak of tidal volume.

The typical person has about 150 ml anatomical dead space. If the typical tidal volume is about 500 ml, how much air that starts completely outside the body actually makes it to the alveoli with each inspiration?

• A. 500 mL.
• B. 150 mL.
• C. 650 mL.
• D. 350 mL.

Here’s what students ask on this topic:

What is tidal volume and how is it measured?

Tidal volume (TV) is the amount of air that is inhaled or exhaled during normal, restful breathing. It averages about 500 milliliters (mL) for both males and females. To measure tidal volume, a spirometer is typically used. This device records the volume of air inhaled and exhaled by the lungs. During the test, the subject breathes normally into the spirometer, and the device measures the amount of air moved in and out of the lungs with each breath. Understanding tidal volume is crucial for assessing basic lung function and respiratory health.

What is the difference between lung volumes and lung capacities?

Lung volumes are individual, non-overlapping measures of the amount of air in the lungs at different phases of the respiratory cycle. These include tidal volume (TV), inspiratory reserve volume (IRV), expiratory reserve volume (ERV), and residual volume (RV). Lung capacities, on the other hand, are combinations of two or more lung volumes. Examples include inspiratory capacity (IC), which is the sum of TV and IRV, and vital capacity (VC), which is the sum of IRV, TV, and ERV. Total lung capacity (TLC) is the sum of all lung volumes. Understanding both helps in assessing overall lung function.

How is vital capacity different from total lung capacity?

Vital capacity (VC) is the maximum amount of air a person can exhale after a maximum inhalation. It includes the inspiratory reserve volume (IRV), tidal volume (TV), and expiratory reserve volume (ERV). Total lung capacity (TLC), on the other hand, is the total volume of air the lungs can hold, which includes the vital capacity plus the residual volume (RV). In other words, TLC = IRV + TV + ERV + RV. While VC measures the functional capacity of the lungs, TLC provides a measure of the total air-holding capacity of the lungs.

What is residual volume and why is it important?

Residual volume (RV) is the amount of air that remains in the lungs after a forceful exhalation. It typically ranges from 1100 to 1200 milliliters. RV is crucial because it prevents lung collapse by maintaining a constant volume of air in the alveoli, ensuring that gas exchange can continue even between breaths. This residual air also helps to keep the alveoli open and reduces the work required to inflate the lungs during the next breath. Understanding RV is important for assessing lung health and diagnosing respiratory conditions.

What is anatomical dead space and how does it affect lung function?

Anatomical dead space refers to the volume of air in the respiratory tract that does not participate in gas exchange because it does not reach the alveoli. This includes air in the trachea, bronchi, and other airways, amounting to approximately 150 milliliters. Anatomical dead space affects lung function by reducing the efficiency of ventilation, as not all inhaled air reaches the alveoli for gas exchange. Understanding anatomical dead space is important for evaluating the effectiveness of breathing and for optimizing ventilatory support in clinical settings.