Frequency domain parameters of heart rate variability should be quoted in normalised units together with their absolute values: author's reply

Abstract

many clinical studies done on the changes of heart rate variability (HRV) during anesthesia have analysed and reported their results using only absolute values without any problems, 1-4 and some have even suggested that the normalisation of spectral powers does not reveal any additional information compared to the low frequency/high frequency (LF/HF) index. 5 LabChart v7 software (ADInstruments, Co., Sydney, NSW, Australia) was used for analysis of HRV in our study, and the LF/HF ratio offered by this program is not different when calculated with both absolute and normalised units. Our primary outcome was the change in the LF/HF ratio in each group during controlled hypotension induced with different agents, and we feel that although not perfect, our method was sufficient enough to explain and support our results and discussion. We appreciate the opinion of Dr. Kurtoglu et al., and plan to analyse and present HRV results in normalised units as well in future studies.