Also in 1995, Masimo introduced perfusion index, quantifying the amplitude of the peripheral plethysmograph waveform. When applied during nerve-sparing surgery, electrical stimulation penile plethysmograph is an erectile dysfunction prognostic. Kurt Freund developed the penile plethysmograph in Czechoslovakia in the 1950s. It was reported that he previously used the penile plethysmograph before developing the Abel Assessment. Another common type of plethysmograph is the penile plethysmograph. Another important parameter, which can be calculated with a body plethysmograph is the airway resistance. This technique uses a combination of an inflatable finger cuff and an infrared plethysmograph. In such cases it is more accurate to use a body plethysmograph. Different sizes of plethysmograph exist to study mice, rats or guinea pigs. The plethysmograph has two chambers, each fitted with a pneumotachograph. The standard plethysmograph sizes are for the study of mice, rats and guinea pigs.