In vitro study in normothermic conditions. (a) Temperatures of the active Performer, and (b) absolute humidity for the Performer (black circle), passive Perfomer (empty circle), Hygrobac (empty square) and Hygroster (black square). Data are presented as means ± standard deviation. Between the devices: °P < 0.05 versus passive Performer and Hygrobac; *P < 0.05 versus Hygroster. Within the same device: +P < 0.05 versus VE 5 and 15 l/min; §P < 0.05 versus VT 1 l; #P < 0.05 versus Vi 1 l/s. VE = minute ventilation; Vi = peak inspiratory flow; VT = tidal volume.