Figure 2From: Methods for evaluation of helium/oxygen delivery through non-rebreather facemasksSchematic of the experimental apparatus used to test helium/oxygen (He/O 2 ) delivery through facemasks. RR and RL represent parabolic resistors (Rp5) placed in the flow paths supplying the right and left compartments of the test lung. ΔP → V represents transducers used to convert the differential pressure measured across either resistor to a voltage signal sent to the data acquisition (DAQ) system.Back to article page