help me read PFTs please

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HollyCatheryn

New member
What do these differnt things measure? What is more or less important? And what are the litre values ideally supposed to be?FVCFEV1FEF 25-75%FEF 50%FEF 75%PEFI know FVC is forced vital capacity, but what does that mean? I used to think that this was the number people wanted when they ask you about your PFTs, but I've just learned that you are talking about FEV1. What's the difference? Why can some be so high at the same time that others are so low? I have my FEV1 in the 90s, but my FEF 75% is in the 20s! How is that?! By what do you judge your overall lung health?I'm just figuring out that I don't know all this stuff even though I always thought I understood it. Please help.
 
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anonymous

New member
FVC is forced vital capacity or the total volume of air that can be expelled from the lungs until there's nothing left (after having taken a deep inhalation). FEV1 is forced expiratory volume in 1 second, or the amount of air that can be forcibly exhaled from the lungs in 1 second. (vs FVC which is the TOTAL volume that can be exhaled). Both of these are usually calculated in liters. The FEV1/FVC ratio is a %, basically the % of the total volume that is expelled in the first second of expiration...

FEF is forced expiratory flow or the flow rate (as in liters/second). FEF 25-75% is the amount of air expelled during the middle half of your exhale. FEF 50% is the amount expelled during the first half of your exhale, and FEF 75% is the amount exhaled during the first 3/4 of the exhale.

Here's a link that explains it a little better:
http://jan.ucc.nau.edu/~daa/lecture/pft.htm
HTH.
 
M

miesl

New member
FVC - Forced Vital Capacity. This one is important.

FEV1 - Forced Expiratory volume in 1 second. This one is important.

FEF - Well, the CF doc doesn't look at these. When he looks at Jeremy's numbers it's the top two he looks at. From what I understand the FEF can vary with how you blow - so it can vary a lot.

PEF - I think this is Peak Flow. Again, this one varies a lot. You still might be able to blow really hard and get a high peak flow even if your FEV1 and FVC suck.

For reference... Jeremy's home PFT only measures the FVC, FEV1, FEF 25-75% and PEF. The FEF and PEF vary a lot, and don't generally indicate how well he's feeling. (He can blow three times, get about the same for FEV1 and FVC, but the PEF especially will go all over the place.) When he was sick in March, his PEF and FEF numbers were about the same, but he had dropped a lot in the other two.

There are a few websites that do a decent job explaining how to read PFTs. You also might want to ask the person who does your PFTs - they could probably explain it best.
 
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anonymous

New member
The FEV1 is so important because it is, like everyone else explained, the amount of air you expel in the first second of your breath out. The problem w/ cf and diseased lungs is mainly that we can get the air in, but the lung damage/mucous or whatever the case may be prevents the air from coming back out easily.

I was under the impression that the FVC calculated the entire amount of air you took in and expelled out, but I guess I might be wrong.
 
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jaime

New member
I know for my doc the most important # is the FEV1, thats the one Im always worried about.
I just had pfts on tuesday and I think they said that the 25-75% represents your smaller airways, deeper in the lungs and the FEV1 is the larger airways.
 
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