Why do we blow rather than suck out candles?


I’m learning how to read spirometry and found it a bit difficult to understand. The spirometry graph below is supposed to help answer the question, but I can’t figure out why. Could someone help me explain? Is FEV1/FVC = 73% low or high? How do I calculate PEFR from the below spirometry graph?

[Here is the spirometry graph](https://imgur.com/bHlYp4o)

In: Biology

So the answer at its simplest, putnyour hand an inch in front of your face and blow on it. Feel that? Now suck in air instead. Feel that? No? That’s why we can’t suck out the candles.

Why is this? When you blow you are taking the air in your lungs and pressing it through the much narrower space of your lips pursed to blow out the candle so it creates higher pressure. When you suck in, the point that would generate the pressure is actually doing so on the wrong side of your lips.

FEV1 is the volume of air you can expel out of your lungs at one second. FVC is the forced vital capacity, which is the total amount of volume you can exhale. So a FEV1/FVC ratio tells you how much of the total amount of air you can you exhale out in 1 sec. Most people are around 80%, which means people exhale 80% of the total exhalable air out within 1 second.

If you have emphysema, your lungs are not as elastic as before so its hard for your to exhale out so your FEV1/FVC goes down. 73% is not bad, people with lung disease like COPD and asthma have ratios below 70.

To answer your question, you are able to exhale a lot more air out (see how far down the blue like goes from the top) than you can inhale. So if you are trying to do something with your breath, you get more air from exhaling rather than sucking in. Plus why would you suck in a candle with wax and what not into yourself.