A question regarding my data collection for my Bio IA HL?

[Guest Fiorella]

Hello everyone, so for my bio IA I decided to measure the forced expiratory volume of a person that has asthma and a person that doesn't (same weight, same height, same gender) and made both of them jog between trials (I did 5 trials).

Now, I used the loggerpro vernier stuff that collects data by using an spirometer. I am VERY confused on how to find the forced expiratory volume...Say (this is NOT my real data just an example so you guys can sort of explain to me how to find this):

Let's say a person did 3 different trials (3 for the person with asthma and 3 for the person that doesn't have astma). In these 3 trials, the vernier pro records flow rate, volume, and time. Let's say at 5.00 seconds for all 3 trials it reports the following:

First trial= Volume 0.405 L

Flow rate 0.452 L/s

Second trial= Volume 0.342 L

Flow rate 1.040 L/s

Third trial= Volume -0.065 L (is it possible this is negative…?)

Flow rate -1.417 L/s

I found something online that said you're supposed to multiply the flow rate (or volume? gah i don't know!) x 100 in order to get the forced expiratory volume...I'm sorry if this seems like a dumb question but Bio isn't really my thing and I want to get a good grade on my IA but I'm not exactly sure if the way I'm finding my measurements is right

Disclaimer: Those are NOT my exact values, I made them up (I added a negative because I did get some negative values on my data...)

Anyways, all advice is appreciated!

[Sandwich]

Well when they assess this sort of thing medically, then you take something known as the FEV1, which is the forced expiratory volume in 1 second. If you're doing it properly, you should also really take the Forced Vital Capacity (FVC), which is more or less a measure of how much air you can expel in total from your lungs, with the exception of 'dead space' air (essentially some air is always left in your lungs). To measure dead space air you have to use 15% helium and then do various equations to figure it all out. So I doubt you'd do that at school!

Anyway, you can look at FEV1 by itself if you really wanted to and there are charts which help you predict what a person's FEV1 ought to be based on height, gender and ethnicity. You should consider ethnicity in your controls - and in future, make sure you research all of the variables that affect your experiment BEFORE doing it! These variables are widely available. So you could compare recorded FEV1 with predicted FEV1. In order to look at obstructive defects (defects are divided into obstructive things, such as asthma, and then restrictive diseases as you might get in conditions leading to pulmonary fibrosis), you would ideally do the ratio of FEV1/FVC. Around 80% is normal. Significantly less than 80% indicates an obstructive defect as in asthma or COPD. Starting to get a bit higher than 80% indicates a restrictive defect.

I have no idea how to use the instrument you're talking about, but it seems to me that FEV1 will just be volume expired at 1 second. In terms of flow rate, you should maybe read up on Peak Flow and how that can also be a useful measurement in asthma. Again, there are predictive charts for peak flow. You should ideally try reading any kind of instructions that came with your instrument, however, because it may just be calibrated really strangely

To have negative results as in your third trial is obviously not quite right. There's no way you can expire a negative amount of air...

Spirometry (here at least) is usually graphed something like this: http://almostadoctor...obstructive.png (with FEV1 being at 1 second and an individual asked to continually breathe out for 6 seconds after which time really most people have definitely plateaued and you can read their FVC off as this maximal amount expired (i.e. when the plateau was reached).