Pulse Rate Variability Analysis During Hemorrhage in an Experimental Porcine Model.

Background: The initial response to hemorrhage is mediated by the autonomic nervous system. A method for detecting autonomic nervous system activity may provide the ability to detect acute changes in blood volume. Previous work has indicated that heart rate variability may be able to detect acute hemorrhage in a porcine model. This study evaluates the ability of pulse rate variability, used as a surrogate for heart rate variability, and obtained from peripheral arterial pressure waveforms, to detect hemorrhage in a porcine model. Methods: Using a model consisting of four subjects, peripheral arterial pressure waveforms were collected over 15-minute intervals before, during, and after hemorrhage. Percent changes for pulse rate variability metrics were evaluated for the 15-minute signals. These longer signals were subsequently divided into three 5-minute signals for short term pulse rate variability analysis. A One-Way Analysis of Variance with a significance level of 0.05 was used to evaluate the sensitivity of pulse rate variability metrics for detecting hemorrhage. Results: At the onset of hemorrhage, an increase in standard deviation, root mean squared error, low frequency power, high frequency power, total power, and the ratio of low to high frequency power was observed, followed by an opposing decrease at the conclusion of hemorrhage. The low frequency power and the ratio of low to high frequency power had the greatest sensitivity to detecting changes in hemorrhage levels. Conclusion: These results suggest that pulse rate variability metrics obtained from arterial pressure waveforms have the potential to serve as a diagnostic method for acute hemorrhage.