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.
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.
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.
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.
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.