The ResMed S8 Elite II CPAP machine features patented EPR Easy-Breathe tecnology which according to 2006 SLEEP focus group clinical study provides equally effective CPAP therapy as other similar units, but is extremely quiet (only 24 decible noise level) AND preferred by more than 79% of CPAP users over the traditional CPAP. The EPR Easy-Breathe reduces air pressure during exhalation which allows the individual to breathe much more naturally and with greater ease. Available with or without H4I Heated Humidifier.