Works. Airtight. Stronger than it needs to be by a whole lot.
This takes care of the requirement of measuring the volume and pressure of air being delivered.
Moves a water column +/-1 cm at normal respiratory rates, so within the range I need. Blowing as hard as you can you can get 10cm of movement.
Three ports. Outer two go to the pitot tubes. Center is for reading the pressure with regards to ambient.
Now if I only could get some pressure sensors to hook it up to.