Tidal volume varies

[mets123]

I can do that when I get home, no pc here.

[ChicagoGranny]

no pc here

How are you getting TV data?

[mets123]

From the sleep screen each morning

[palerider]

Tidal Volume is an estimate of quantity of inhaled air
per breath, calculated as an integral of respiratory flow:
based on the leak flow, the mask vent flow and the
total flow rate. The display is based on a five-breath
moving average, updated every breath.

My emphasis:
Now, this it me trying to undertand:
If tidal volume is the amount of air
And if there's less air at higher altitude
Doean't it stand to reason that tidal volume would be lower?

Or is there something I'm missing?

There's not less air, as far as the machine is concerned, it's still measuring liters of air, by volume, and a liter of air is a liter of air, even if the weight of that liter of air is lower at the higher altitude.

And, everything is relative to ambient, so you're pressure will be 10cmh₂O over ambient at sea level, or at 9k above sea level, even though the absolute pressure will have dropped from 14.7 to 10.5(ish) psi.

[gurug]

I have had similar experience. I live at around 4,500' and notice my breathing rate and tidal volume goes UP about 10% when I'm at lower elevation (600'). It then goes back down after returning back to altitude.
Not sure why. I would have though it would be opposite but there is a consistent change for me.