Heart Rate Variability Analysis During Lower Body Negative Pressure Test Induced Central Hypovolemia

In clinical patient monitoring scenarios, the detection of hemorrhage is still a major problem. Traditional vital signs like heart rate and blood pressure are insensitive to blood loss due to compensatory mechanisms in the body that can sustain these parameters until shortly before cardiovascular collapse. These compensatory mechanisms during blood loss are primarily driven by the autonomic nervous system. Heart rate variability analysis is a viable tool in the quantitative analysis of the autonomic nervous system and shows promising results in the context of hypovolemia detection. In order to investigate if HRV parameters suitably reflect a mild to moderate blood volume reduction, we conducted a lower body negative pressure test study with 30 volunteering participants thereby simulating progressive central hypovolemia. Here, HRV parameters from the time domain (mean HR, SDNN, RMSSD, rSDRM, pNN50), the frequency domain (VLF, LF, HF, LF/HF), non-linear HRV parameters (SD1, SD2, SD1/SD2, SampEn, ApEn) and the respiratory rate (RR) were collected. The changes of the evaluated parameters as a consequence of the reduced blood volume were statistically evaluated. A statistically significant deviation from their baseline values could be found for RMSSD, rSDRM, pNN50, HF, LF/HF, SD1 and SD1/SD2 at a chamber pressures starting at −30 mmHg. Therefore, we support the proposition that heart rate variability analysis can help in detecting otherwise occult hypovolemia.