[hourislate]

First comment on page.

>My wife is an Ironman as well (Muskoka, Tremblant and Penticton). . She's been using Zwift since last year. Great way to train btw and great idea but. My concern would be a collapsed lung(s) if this wasn't calibrated correctly. To each their own, but stressing your lungs and diaphragm this much isn't a great idea.

In a lab they can at least make sure you don't hurt yourself.

[jacquesm]

I see where you're coming from I assume that you are talking about the device resistance when breathing in and you're worried that the adhesion between the lung sac and the cavity wall breaks.

You can pull a pretty good vacuum with just your lungs, so I'm not overly worried about that. And pressure is not a problem unless you have a weak spot in your lung.

But still, it's a good point to make and maybe the author could measure the flow resistance in both directions and optimize for that to ensure that it never becomes a problem, even in people that might have a hidden defect.

[newaccount74]

But the device resistance won't be very big, would it? If I understand correctly, you are just breathing through a tube, and this device measures the flow through the tube. Or is there something in the tube that would cause a lot of resistance?

[danielheath]

Adding some resistance is typically how you measure flow.

[762236]

How would you get a collapsed lung from using this? And how does its calibration influence whether you get a collapsed lung? This device doesn't interfere with inspiration, and a large breath of air inflates your alveoli.

[idealmedtech]

Questions like this are why people should not be building medical devices at home. Your average athlete interested in this may lack the necessary medical knowledge to understand that a collapsed lung is a possibility when using this device, and cause themselves serious bodily harm.

[jacquesm]

Pulling a vacuum against your lung can break adhesion when done from the lung cavity.

[voisin]

How could it cause one’s lungs to collapse? Isn’t the idea of measuring VO2 max that a tight seal is formed and all input and output is measured for O2 and CO2? It isn’t pressurizing or depressurizing.

[jacquesm]

It is pressurizing on output due to the flow through the device, the same thing causes some underpressure when breathing in.

But I doubt it is enough to draw a vacuum strong enough to break adhesion. Still, better safe than sorry, it would be good to read the instruction manual of a professional unit to see what kind of failure modes they have listed there.

[mikewarot]

I read a lot of stuff back in 2020 because I was going to be coding up controls for an emergency ventilator... you would not believe just how little pressure difference it takes to permanently ruin your lungs... less than 1 PSI if I recall correctly.

[jacquesm]

You really don't want to over-pressure your lungs with 1 PSI, that's huge for tissue. For a regular party balloon that you blow up the pressure is less than 0.5 psi. But a flow meter in a sports measurement device should be a fraction of that, after all, the back pressure is going to take away effort that should go into providing work.

[TylerE]

1psi is actually quite a lot.

Standard CPAP machines max out at just over 0.25psi, and even ventilators usually max out about 0.4-0.5psi.