Figure 1: Experimental setup. In a circuit including a heated humidifier, a limb with a heating wire, and a one-way valve connector, a ventilator delivered medical gases, through the HME being tested, to the bellows. The gases were warmed to 36°C at the chamber outlet of the heated humidifier and to 37°C at the end of the limb. Two levels of leakage were created: 3.2 L/min (small) and 5.1 L/min (large) at airway pressure of 10 cmH2O. HME: heat and moisture exchanger.