Fig. 3

Graph showing absolute humidity in mg/L as a function of the various configurations tested. The absolute humidity (median) is expressed in mg/L for different humidifier (MR810, HC550, D900, HC150 and AIRcon). The valve circuit or vented circuit is watertight = closed (no unintentional leak) or with an unintentional leak. The tidal volume is 600 or 1000 mL. Results were obtained on the set-up comprising 2 hygrometer probes, drying and change of circuits between each configuration except for the AIRcon (set-up with 1 hygrometer probe). All differences were statistically significant with p value always lower than 0.001. The threshold corresponds to AARC recommendations (absolute humidity of 33 mg/L). AARC = American Association for Respiratory Care