PROBLEM TO BE SOLVED: To provide a novel technology for analyzing a biological state.SOLUTION: The second order derivative of a trunk biosignal (aortic pulse wave) from the dorsal trunk of a person is obtained. Using the waveform of the second order derivative, a low frequency maximum amplitude waveform component that appears when there is a shift from ventricular systole to diastole and the amplitude switches from decrease to increase is specified for each cycle； inflection points located before and after the maximum amplitude waveform component are specified； and using information on each inflection point, a biological state is analyzed. The biological state can be analyzed because the time phases of the two inflection points obtained from the reference shape of the second order derivative waveform of the aortic pulse wave substantially coincide with the first heart sound and the second heart sound (or are equivalent to the R wave and T wave in an electrocardiogram) that represent cardiovascular system dynamics.【課題】 生体状態を解析するための新たな技術を提供する。【解決手段】体幹背部からの体幹生体信号（心部揺動波）を二階微分し、その二階微分波形に用い、それぞれの周期において、心室の収縮期から拡張期に、振幅が減衰から増幅に切り替わって現れる現れる低周波の最大振幅の波形成分を特定し、その最大振幅の波形成分の挟んで前後に位置する変曲点を特定し、各変曲点の情報を用いて生体状態を分析する。心部揺動波の二階微分波形の基準形態から得られる２つの変曲点が、心循環系の動態を表す心音のＩ音とＩＩ音（又は心電図のＲ波とＴ波に相当）に時相がほぼ一致するため、生体状態の分析を行うことができる。【選択図】 図４
