What is forced vital capacity and how does it relate to lung volumes
What does the table indicate about vital capacity and subjects age, sex, height, smoker, asthmatic or athlete, do the findings support previous studies.
What is peak expiratory flow and what is the effects of sitting, standing and lying on this measurement. (what effect do any of those positions have on the trachea)
Studies to support findings
What is forced vital capacity and how does it relate to lung volumes?
In order to explain this question, we need to understand about the different lung capacities and corresponding lung volumes.
The average individual moves about 500 ml of air into and out of their lungs with each breath. This is called the tidal volume. However, in addition to this amount of air that can be breathed into the lungs, the lungs have a much greater capacity for inhalation and exhalation. By taking a deep breath, you can inspire way more than just 500 ml. In fact, most people can inhale about another 3100 ml. This is called the inspiratory reserve volume. Therefore, if we add the two volumes together, we get about 3600 ml of total inspiratory capacity.
Now, there is also an ability to exhale above and beyond the regular 500 ml. This is called the expiratory reserve volume. If you forcibly exhale as much as possible, you can exhale about 1200 ml above and beyond the 500 ml that you usually exhale after each regular inhalation.
Interestingly, even after you forcibly exhale all the air you can, you've still got about 1200 ml in the lungs that you can't exhale -- ever! Well, not until you're dead. This volume is the residual volume.
If we add up all the lung volumes mentioned, we get about 6 litres of air that your lungs can hold.
Now, what's forced vital capacity? This is the sum of inspiratory reserve volume (3600 ml), tidal volume (500 ml), and expiratory reserve volume (1200 ml). In the above illustration, forced vital capacity would be about 4800 ml.
What does the table indicate about vital capacity and subjects age, sex, height, smoker, asthmatic or athlete? Do the ...