Constructing a New Metric Heart-Breath Coherence Based on Cardiopulmonary Coupling for Coherence Measurement

The circulatory system is strongly coupled with the respiratory system in human body, which can be measured by the heart rate and respiratory signals. We construct a new metric called Heart-Breath Coherence (
$HBC$
) based on the coupling degree of the cardiopulmonary system to characterize the relaxed/joyful level of human body. The heart rate and respiration are simultaneously measured and collected to calculate
$HBC$
which reflects the similarity degree of power spectrum density and phase difference. For the multi-scenario experiment, we apply
$HBC$
to distinguish volunteers' preferences (most-preferred/ least-preferred). The accuracy of
$HBC$
is 91.49%, while the accuracy of other metrics proposed in previous researches can only reach up to 72.34%. Furthermore, the
$HBC$
shows the maximum differentiation of volunteers' preferences with p-value < 0.01. Our approach shows that the new metric
$HBC$
can locate the respiratory band of heart rate variability and quantify the coupling of cardiopulmonary system more precisely, which help improve coherence measurement.