Many types of heart rate variability (HRV) measurements have been introduced as potential predictors of risk of sudden infant death syndrome (SIDS). Study the relationship between all these HRV measurements in infants is another attractive research field as well as using HRV to differentiate infant groups as health or aborted-SIDS. Further understanding of HRV measurements is necessary in order to use them to predict potential victim of SIDS more effectively. In this project, the correlation coefficient was used to measure the relationship of these measurements, and we will analyze the HRV changes with time, sleep states, and infant groups.

HRV of infant is affected by sleep state. For all the above study, the data we used are 8-hour RR intervals from the PSG with classified sleep states of each infant. The sleep states are classified as quiet sleep (QS), rapid eye movement (REM), awake (AWK), and undetermined state for each 30 seconds of the signal. The measurements we investigated include:

• Time-Domain Measurements: standard deviation, interquartile range, PNN50, and RMSSD etc.
• Frequency-Domain measurements: high frequency power (HF), low frequency power (LF), and LF/HF ratio etc.
• Nonlinear Measurements: approximate entropy and Poincare plot etc.