Sepsis is a significant cause of hospital deaths, but early detection could save lives. Heart rate variability (HRV) is a measurement of the change in heart rate and may be useful as a marker for early detection of sepsis. In this study, E. coli endotoxin was administered to healthy human subjects and changes in temperature and HRV were monitored at 6 hours post administration. HRV features measured were pNN50 and multi-scale entropy (MSE). We modeled changes in baseline using a sigmoidal model with 3 variables to help quantify dynamics of HRV and temperature time series. Curves of HRV and temperature versus time demonstrated that changes in HRV features preceded changes in temperature. Our model fits indicate HRV changes both begin earlier and occur faster than temperature or heart rate. Our findings are consistent with other group findings that demonstrate changes in interbeat intervals can be detected earlier than other signs of systemic inflammation.