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 O2 Support & Lung Function Testing
 Lung Function Percent - Meaning
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mboerner
Member

USA
66 Posts

Posted - Oct 23 2011 :  4:53:15 PM  Show Profile  Reply with Quote
What spirometry number is being referred to when a forum member says, for example, "lung function is down at the 20% range"?

PennyPA
Contributing Member

USA
4731 Posts

Posted - Oct 23 2011 :  6:28:07 PM  Show Profile  Reply with Quote
The FEV1 number.

It sort of shows that that person has about 20% of their lung function left. It's merely a rough guideline. Some people can still do a lot at 20%; others can't do much at all with 50%. It is really all about how you feel.

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tsainta
Contributing Member

USA
1316 Posts

Posted - Oct 23 2011 :  7:08:44 PM  Show Profile  Reply with Quote
FEV is only one of a number things measured by a PFT, so you ask a good question. I don't think anything called "lung function" is one of them. So I think what is often offered as "lung function" is a generalization some people hear from their docs.

Tony-CA

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Dave-OH
Administrator

USA
3421 Posts

Posted - Oct 23 2011 :  7:09:00 PM  Show Profile  Reply with Quote
We usually refer to the FEV1 percentage. That is one of the major measures in a spirometry test. The other is FVC. The first measures air movement in 1 second, the second in a complete breath.

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tsainta
Contributing Member

USA
1316 Posts

Posted - Oct 23 2011 :  8:14:01 PM  Show Profile  Reply with Quote
But people who are referring to some percentage of "lung capacity" may or may not be referring simply to sprirometry. Since "lung capacity," per se, is not measured either by sprirometry or a PFT, the generalization needs more definition to be meaningful. For example, I might say my lung capacity is about than 29% because my FEV1 when last measured was 29%, but that would be incomplete and misleading. My actual limiting factor is DLCO, from a PFT not sprirometry, and that is less than 23%--the actual capacity of my lungs to oxygenate my blood.

FEV deals with the lungs' ability to move air; DLCO measures the lungs' ability to effectively use the oxygen present in the lungs. They are distinctly different measurements and (I think) unrelated to one another.

FVC does measure capacity, but that number is seldom the one I see referred to in most post on this forum or around the internet.

So, as I said, I think the term "lung capacity," as used casually in most forums is a questionable metric for comparison.

Tony-CA

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Dave-OH
Administrator

USA
3421 Posts

Posted - Oct 23 2011 :  8:40:43 PM  Show Profile  Reply with Quote
Tony, DLCO is never referred to as lung capacity. Lung capacity is the ability to move air, not use O2. Yes they are different measures for different things. There are several PFT measures with the name lung capacity, including Total Lung Capacity. The reason that FEV1 is used is it reflects are ability to move air quickly. FEV1 is by far the most frequently used index for assessing airway obstruction, bronchoconstriction or bronchodilatation; FEV1 expressed as a percentage of the VC is the standard index for assessing and quantifying airflow limitation.

It can be useful in differentiating between obstructive and restrictive lung disorders. In asthma (an obstructive lung disorder) the forced expiratory volume in 1 second (FEV1) is usually decreased, the forced vital capacity (FVC) is usually normal and the ratio FEV1/FVC is decreased. In restrictive disorders the FEV1 and FVC are both decreased, leaving a normal FEV1/FVC.


The most common parameters measured in spirometry are Vital capacity (VC), Forced vital capacity (FVC), Forced expiratory volume (FEV) at timed intervals of 0.5, 1.0 (FEV1), 2.0, and 3.0 seconds, Forced expiratory flow 25Ė75% (FEF 25Ė75) and Maximal voluntary ventilation (MVV),[1] also known as Maximum breathing capacity.

Dave, Forum Administrator
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tsainta
Contributing Member

USA
1316 Posts

Posted - Oct 23 2011 :  8:46:31 PM  Show Profile  Reply with Quote
Thanks.

Tony-CA

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Dave-OH
Administrator

USA
3421 Posts

Posted - Oct 23 2011 :  9:00:49 PM  Show Profile  Reply with Quote
Good quote.

Dave, Forum Administrator
COPD Support, Inc. http://www.copd-support.com/
Your source for peer support and COPD Info

Chat room http://chat.copd-support.com
Mobile chat room for pads and phone Chat room http://chat.copd-support.com/m

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mboerner
Member

USA
66 Posts

Posted - Oct 24 2011 :  05:10:47 AM  Show Profile  Reply with Quote
This post has been quite useful to me because it explains the variations in the term

quote:
Originally posted by tsainta

But people who are referring to some percentage of "lung capacity" may or may not be referring simply to sprirometry. Since "lung capacity," per se, is not measured either by sprirometry or a PFT, the generalization needs more definition to be meaningful. For example, I might say my lung capacity is about than 29% because my FEV1 when last measured was 29%, but that would be incomplete and misleading. My actual limiting factor is DLCO, from a PFT not sprirometry, and that is less than 23%--the actual capacity of my lungs to oxygenate my blood.

FEV deals with the lungs' ability to move air; DLCO measures the lungs' ability to effectively use the oxygen present in the lungs. They are distinctly different measurements and (I think) unrelated to one another.

FVC does measure capacity, but that number is seldom the one I see referred to in most post on this forum or around the internet.

So, as I said, I think the term "lung capacity," as used casually in most forums is a questionable metric for comparison.

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Dave-OH
Administrator

USA
3421 Posts

Posted - Oct 24 2011 :  09:06:24 AM  Show Profile  Reply with Quote
Again, the reason that FEV1 is used when discussing lung capacity in COPD - obstructive lung disease, is that it reflects the diminished ability to move air out of the lungs quickly. FVC is affected in restrictive lung disease, as that disease impedes in inhalation of air into the lungs.

Dave, Forum Administrator
COPD Support, Inc. http://www.copd-support.com/
Your source for peer support and COPD Info

Chat room http://chat.copd-support.com
Mobile chat room for pads and phone Chat room http://chat.copd-support.com/m

My Site: http://lungresources.com
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PennyPA
Contributing Member

USA
4731 Posts

Posted - Oct 24 2011 :  10:47:44 AM  Show Profile  Reply with Quote
And the original poster wanted to know just what number "we", as posters, were referencing and that number is the FEV1.

****************************************************************

You canít change the past but you can ruin the present worrying about the future.

The Bad News: Time flies as you get older.
The Good News: Youíre still the pilot.

Penny's Lung Volume Reduction Surgery

And Our Travel Blog After LVRS




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