After Mr Cheney mentioned to us that one of his A level biology students had randomly made a homemade spirometer (this measures lung volumes as you breathe in and out) after an off the cuff comment in one of his lessons, we were intrigued and had to find out more!

Watch and read how Li An managed to make a spirometer out of everyday items lying around her house, including a Lego motor ‘borrowed’ from her brother! 

By Li An Tan, Year 12

We were in a biology lesson learning about gas exchange and inhalation/exhalation and Mr Cheney was telling us about how normally if we were in school, we would be able to see a spirometer that is able to graphically record your breathing. He showed us a diagram a bit like the one I’ve attached below where the person breathes into a tube and it causes a chamber to go up and down. That movement then moves a pencil that draws on a rotating roll of graph paper, depicting the person’s breathing. Because we couldn’t go into school to have a look, Mr Cheney jokingly said he should get us to construct our own for homework. Seeing as I had nothing better to do, I thought I would give it a go! I did do it independently until I decided to go further and add axes onto my graph. Working out the x-axis was fine, but I was struggling to find a way to calibrate volume for my y-axis so I asked Mr Cheney if he had any ideas. His solution was to fill a plastic drink bottle partly with water so that the amount of air in it was exactly one litre and then pump it into my spirometer to record the height. 

 I was quite bored but had a lot of homework that day and so I used it as a way of procrastinating. It isn’t something I have ever done before but looking at the diagram, everything made sense so there was no reason why I couldn’t recreate it. I also thought I was being so funny for taking seriously an off the cuff comment and I think that spurred me on too!

The hardest thing was making a revolving graph that a pen could draw on. It wasn’t perfect by the end but I did sort of manage. I had to dismantle my brother’s Lego contraption to get to a motor and then I coded it to rotate and at a particular speed. Luckily there was a very easy app that Lego had made to do this because I don’t know how to code! And then I built on the motor and stuck on card and paper to mimic the rotating drum with graph paper in the diagram.

What did I learn…? Honestly I’m not sure… I suppose I learned that I’m more resourceful than I thought. In terms of what I learned from the spirometer itself, I found that my tidal volume is around 0.6 L. I don’t think it is especially accurate but it’s cool that I can technically work out the volume that I inhale from it.

 I used a plastic freezer bag, lots of cardboard from the recycling bin, a giant plastic straw that my grandma randomly gave me years ago (we still aren’t sure why), a pencil, a motor stolen from my brother’s Lego, and some card and paper. I think the most ingenious bit was getting the motor to spin so that the pen could actually draw on the paper. When I first tried to imagine it in the middle of biology, I knew how I would go about the rest of it. It was just the whole spinning graph thing that was really tricky.

The best moment was when I first tested it and the pen actually drew on the paper. It didn’t look good and it wasn’t smooth, in fact you would probably be concerned if that was how your breathing looked but it was still quite impressive that ink even ended up on the paper after such a long chain of events from first inhaling or exhaling.

 I’m not making anything currently, but this week I actually went to the fishmongers and bought a salmon head because we can’t go into school to do dissections and Mr Cheney semi-jokingly challenged us to do it at home. My parents aren’t too happy about the giant fish head currently sitting in our fridge though.

https://www.youtube.com/watch?v=1d_AL4191ns&feature=youtu.be