Reducing Respiratory Artifacts in Heart Rate Variability during Functional Food Intake Using ECG ‐Derived Respiration

Heart rate variability (HRV) has been analyzed to assess the effects of food on autonomic nervous activity, but HRV is reportedly influenced by respiration. Reducing respiratory artifacts in HRV analysis requires respiratory signals. In this study, we estimated respiratory signals from electrocardiogram (ECG), compared these signals with actual respiratory signals, and investigated HRV indices before and after reducing respiratory artifacts based on estimated or actual respiratory signals during functional food intake. ECG and actual respiratory signals were recorded from five healthy males during gamma‐aminobutyric acid (GABA) or placebo intake. Estimated respiratory signals were obtained using eight types of ECG‐derived respiration (EDR) methods. The highest similarity to the actual signal was observed in the signals estimated from the EDR method based on the fourth‐order central moment. Comparing the LF/HF ratios (one of the HRV indices), the difference between GABA and placebo decreased at 60 min post‐intake after reducing respiratory artifacts than before reducing them; a decrease of 39.5% using the estimated signals and a decrease of 48.7% using actual signals. Our findings indicate that the EDR method provides the possibility of analyzing HRV with reduction of respiratory artifacts using only ECG, similar to using the actual respiratory signals, in functional food studies.