how is lung function measured?

[giraffesCantDonateBoneMarrow]

Was at resp clinic today. My predicted lung function is 84% and today it was 56%. What is it a % of? Is it % of the predicted level? confused.

It's measured as the speed in which you breath out and how much air is in your lungs and how long you can exhale for.

DS1 has cf so we do these weekly.

The prediction is based on your age, gender and weight.

so 84 is my predicted and 56% is what i actually got.

I dont understand what it is a percentage of.

Like oxygen levels are a % of how much o2 is in the blood.

But it seems to be to do with speed you breathe and how much you can breathe out so so is it like a formula like bmi?

Or should I just give up trying to understand?!

I gave up trying to understand years ago!

53% is low, are you ok?

Was it FEV (forced expiratory volume?)? Im not sure that they mean by the 84%. The predicted should be a certain figure in litres if it's FEV (which is 100% because that's the prediction for your age/sex/size). The result you produce should give another figure in litres which is then expressed as a % of predicted.

aaah maybe 84 is not a %, it is in the predicted box. And the % bit been put on by accident, like habbit of writing a %sign in that box?

so 56 isn't a number I achieved, is it that the 2/3 predicted values are calculated to give a number, my number is 84.

Then the 2/3 values of the test are calculated and measured as a % of the 84 giving me 56?

Last time it was 71 so this is a drop. Was in hosp last week. The consulatant came in the room, I felt honoured, usually you are at their clinic but you just seen a minion. And occasionally they go out to speak to them and then come back but he actually came in. Then had to go do a test that measures inflamation in lungs but blowing in to a giant tamagotchi - well it looked like that!! And had 5 tubes of blood taken.

Booked skin prick allergy tests and a ct scan of lungs. (already had xray)

It means you have nits

I've given up trying to understand, I just nod along and take the drugs!

Yeah but netto you are just a wee bit anxious. After all the consultant came in the room for me, not you. So neh. Do I get my free TV now?

No I don't have one yet.

fuckers.

tamagotchi test

I don't think I've ever had that done
I just get the hot air balloon one, and dishy Darren yelling blow blow blow at me, whilst I admire his comedy socks.

I need a tamagotchi test, it may discover that actually, my lungs are fine, and I don't have asthma at all.

Although once, I had lung function tests at a different ho0spital (The Vale), where they made me sit in what resembled a shower cubicle

DD had that test and a Bronchial challenge recently. That was fun.

I had the bronchial challenge two years ago. Not fun nor pleasant but it confirmed a diagnosis of asthma...so that was helpful Twenty years of breathing like a broken hoover were not wasted MPD

The predicted is based on several things, like your height fir instance. So 100% predicted is what a perfectly healthy person of your weight/height/age etc will blow.

I understand that Fev1 is the forced expiration in the first second of the breath in the test. The overall percentage is generated by the programme and predicts what your blow equates in percentage terms in comparison to that of a healthy (no underlying conditions for example) lung should blow based on height and weight of the person.

But it can be a tricky technique to master and all results need to be considered within each persons range that is normal for them. its usually used as an objective measure and a sudden drop in lung function alongside clinical symptoms usually indicates some kind of treatment is needed.

hth

Thanks all.

There are a number of ways to measure lung function, the most basic is peak flow - which is just that the speed you cblow out.

FEV1 is as another poster has said the amount you breath out iin the first second,

The shower cubicle one is a body plethysmograph and is the most acurate because it takes into account the changes in air pressure around you.

the % is probably the FEV1 as a % of FVC. Normal, healthy lungs in a young person you would expect 90% of the volume to be expelled in the first second, your 84% is for normal healthy lungs for your age, height and race.

Depending on the lung disease the 'trace' or printout changes, if it was a simple spirometry / ventalograph then the pen goes 'up' very quickly in normal lungs and then stays at the same value for the rest of the test. Depending on whether the lung has restrictive or constrictive disease (loads of mucus vs asthma) the pen will rise quickly but to a low value - but ou can continue to breath out for much longer than 'normal' lungs, the other the pen rises in a straight line from the bottom left to the top right of the paper / screen.

So the %, although it is low, does not mean there is anything drastically wrong, just that your lungs have some form of disease / condition. But you knew that didn't you?