what is a lab-ratting mask?

Diagram of the experimental setup to noninvasively apply nasal CPAP and sham-CPAP in anesthetized rats. R are resistors inducing positive pressure in the CPAP chamber and nil pressure in the sham chamber. The airflow to avoid rebreathing was the same in both chambers.

AnimalsThe study, which was approved by the Ethics Committee for Animal Experimentation of the University of Barcelona, was conducted on 32 Sprague-Dawley male rats (250–300 g) intraperitoneally anesthetized with urethane 10% (1g/kg).
Experimental Setting
A novel setup was devised to noninvasively apply nCPAP to one rat and sham-CPAP to another rat simultaneously. A conventional CPAP device set to 10 cm H2O was connected to a bifurcated tube (Figure 1). One branch was connected to a chamber with 2 short cylindrical tubes (1.5-cm length, 2-cm diameter). One of these tubes was used as a facemask and the other one was open to the atmosphere through a resistor (R) consisting of a 1 mm diameter hole. With the rat in place, this chamber was pressurized to 10 cm H2O (CPAP) and the air was renewed by a flow of 25 mL/s. The other branch from the bifurcation was connected to another similar chamber (Figure 1). However, in this case the resistor (R) was connected at the inlet of the chamber instead of at the outlet, which was directly open to the atmosphere (Figure 1). Therefore, in this chamber (sham) the pressure was zero and the airflow to avoid rebreathing was the same as in the CPAP chamber.