Understanding basic spirometry readings - Lung Conditions C...

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Understanding basic spirometry readings

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When we visit our specialist they always seem to hush or readings or not explain them to us, so if anyone can give me an idea what mine means it would be great, I know we are not doctors but between us we all have a bit of info that can help each other out.

FEV1 of 3.14 and an FVC of 4.41 giving a ratio of 71%.

I get that one is the amount of air we hold the other is something about blowing out but what's the average? And also what does the 71% mean? Should I be higher/ lower, are these good readings? Any info would be Helpfull

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11 Replies
RedSox profile image
RedSox

Wow my numbers are exactly the same as yours yet I’m confused to it’s ultimate meaning but I think it’s mildly moderate or moderately mild but again not positive

jackdup profile image
jackdup

Do you also have the FEV1% of predicted and FVC% of predicted, or the FEV1 predicted and the FVC predicted? You need either of these two sets to be meaningful as the FEV1/FVC ratio by itself is almost meaningless.

Spirometry is one of the rare situations in life where it is possible to score more than 100%. I’ll try and explain a little bit to the best of my understanding.

The numbers people are often most interested in are the fvc and fev1 (often more the percentage than the litres, as it’s easier to put in to context). Fev1 is forced expiratory volume over 1 second, so quite literally the volume of air you can exhale in the first one second of blowing on the test. FVC is forced vital capacity, so essentially the total volume you exhale over the course of the blow. The way the results are determined is that there’s a standardised set of ‘expectations’ based on age, height and weight: the machine is given that information about each patient, you do your blows, and then it compares the litre figures you blew with the expectations or the ‘predicted’ for someone of the same age, height and weight without a lung condition. On the print out it will list the volume for each measure in litres, but also converts that into a percentage - I can’t tell you what the litres you blew work out to in terms of percent, but some guys on here do know how to convert it, so hopefully one of them will come along and help you with that bit. To give you an example though, when my daughter is really, completely well, I can currently expect her fvc to be around 80% (meaning she has 80% of the predicted fvc for another child of the same stats without a lung condition) and an fev1 in the mid to high 70s. When she’s not well and has an active exacerbation, at her worst in hospital I’ve seen her have an fev1 of 40% and an fvc of 48% predicted. My understanding is that with some conditions such as COPD, a diagnosis is in part made by the numbers you blow, and the relationship between the numbers can be important, but as a general rule of thumb, any value of 80% or above for fvc and fev1 is generally considered normal. Because they are standardised expectations, if someone is really fit, they can have numbers over 100%. The machine can also suggest the nature of any underlying lung condition e.g. it may say that based on the numbers and the flow curve you produce, it’s due to a restrictive condition or an obstructive one, which can help doctors determine the cause of poor lung function.

Both fev1 and fvc can sometimes be improved, normally by adhering to treatment and increasing the amount of exercise you do where possible. It can certainly be maintained in some conditions through treatment and exercise.

Hope that’s been of *some* use, but what you really need to know is how your numbers stack up in terms of predicted percentages rather than just the litre volumes you blew.

O2Trees profile image
O2Trees in reply to

Great reply Charlie - just one correction which someone pointed out to me a while back: the results are based on what is predicted for height, age and gender. Weight isn't a factor.

in reply toO2Trees

Well, I’ll be - you learn something new every day! I just checked the same was true of paeds (because weight is a factor in so much with kids, particular where growth profile is relevant) and now stand fully corrected, but I appreciate it. Thanks O2 👍😁

Hacienda profile image
Hacienda

Hi Hun, Just had my Spirometry Test after having valves inserted, Yes, you are right about Consultants not telling us, As much as I love my Lady, she will not tell me, Wednesday, I was to see my lady after the test so asked the Georgia what my results were, she said ok but Don't tell Amy as she will be cross with me. My FEV1 (lung capacity) read 32.4% compared to 30% two years ago, an increase of 2.4%. After all my Exercising, Rehab, & Gym Sessions, I was hoping for more, (your 71% is superb). But as Everyone here has told me That is a Good increase, So I'm very happy as I will always listen to the experts who are our HU Family. Hope your Well Nik72 and Enjoying our Glorious Weather. have a Great Weekend. Love n Hugs XXXX Carolina .

Mavary profile image
Mavary

When I blew into the machine my line dropped straight down. He did it twice and remarked how they were practically indentical. I know nothing about readings so wondered if this is right. It looks like I’m going to have to learn about these things though.

Superzob profile image
Superzob

FEV1 is the volume of air you can breathe out in one second and the FVC is the total volume of your lungs. The closer these readings are, the better your lungs are performing. However, with age the FEV1 is likely to drop, whereas your lungs retain the same volume, so the ratio reduces from 100%. Can't say whether this is a good or bad reading as it depends on numerous factors as other posts have pointed out. However, there's no point doing spirometry unless the consultant is able to conclude something from the results and, if s/he hasn't suggested any treatment, then they presumably think the readings are OK given your particular circumstances.

soulsaver profile image
soulsaver

Hi Nik

In simple terms - for normal lungs:

With force, you (one) should be able to blow out about* 3/4 (75%) of your fully inflated lung capacity in 1 second... and the other 25% in however long it takes, c.12seconds.

To know with some accuracy whether you can, you'd need to be able to measure -

A) Your fully inflated lung volume.

B) How much of it you can blow out in 1 second.

So... Spirometry (Latin for measure of breath):

A) Your fully inflated lung volume = Forced Vital Capacity - FVC

B) How much you can blow out in 1 second = Forced Expiry Volume at 1 second =Fev1

So, the % of your lung volume that you can blow out in 1 second is your Fev1/FVC ratio.

That's what your 71% is - you can forceably blow out 71% of the air in your fully inflated lungs in one second.

So far, so good?

Now the tricky bit: Normal isn't a precise measure - it's a range. That 71% is in the 'normal' range but (arguably*) near the lower border.

If you are showing symptoms and your history - say, 25 pack year smoker and/or recurring bronchitis in winter/ 30 years in a flour mill, (ex-)smoker with persistent productive cough.. etc - it'll be going on your health record as a 'treat as COPD, until known different' or wtte.

Now, IF IT IS diagnosed COPD, your Fev1 percentage against normal for your height age and gender will help determine what stage it is - ie:Mild, moderate, severe, etc. Although you haven't said what it was, the ratio you've posted is if COPD, I'd guess as mild.

Simple isn't it?

Well it gets complicated by

A) Spirometry isn't used for just COPD diagnosis.

B) It can show early effects outside a normal Fev1.. or even normal Fev1/FVC

C) *Many health jurisdictions differ on what's 'normal'.

D) *Some health jurisdictions decided what was normal, then changed... but both views co-exist on the internet.

E) People get confused around the measures and answer queries with the best will.. but incorrectly.

Best wishes.

Superzob profile image
Superzob

Sorry, my reply was an over-simplification - soulsaver and Charlie have provided more detailed replies, which I hope helps clear up the confusion.

soulsaver profile image
soulsaver

The jurisdictions are the National Government health organisations and their sub sections and /advisors relating to chronic diseases inc COPD.

So National Institute for Clinical Excellence (NICE)/British Thoracic Society, UK ; Centre for Disease Control (CDC) US; Public Health Canada; etc

Plus there is a Global initiative, Global Obstructive Lung Disease (GOLD) that has a significant presence in at US & UK amongst others.

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