심 박 지표 는 , HR ( heart rate ) , mPP ( Mean of preak to peak ( PP ) intervals ) , SDNN ( Standard deviation of PP intervals ) , CVNN ( Coefficient variation of PP intervals ) , RMSSD ( Square root of the mean of the sum of the squares of differences between adjacent PP intervals ) , pNN 20 ( Number of pairs of PP intervals with differences more than 20 ms in percentage to all PP intervals ) , pNN 50 ( Number of pairs of PP intervals with differences more than 50 ms in percentage to all PP intervals ) , VLF ( Power density spectra of very low frequency ) , LF ( Power density spectra of low frequency ) , HF ( Power density spectra of High frequency ) , TF ( Total power density spectra ) , LF / HF , LF / TF , HF / TF , nVLF ( Normalized VLF ) , nLF ( Normalized LF ) , nHF ( Normalized HF ) , dLFHF ( Difference between LF and HF ) , SMI ( Sympathetic modulation index ) , VMI ( Vagal modulation index ) 및 SVI ( Symphatovagal balance index ) 중 적어도 하나 를 포함 할 수 있 다 .