JP3829220B2 - Cardiac function monitoring device - Google Patents

Description

【００４７】
大動脈実効エラスタンス算出手段９４は、たとえば数式５に示す予め設定された関係から、上記収縮末期大動脈圧決定手段９０により決定された左心室の収縮末期における大動脈の圧力である収縮末期大動脈圧Ｐ_esと、上記拍出量推定手段９２により推定された左心室の一拍あたりの拍出量ＳＶとに基づいて大動脈実効エラスタンスＥ_a を算出する。この大動脈実効エラスタンスＥ_a は、図７の容積軸上の拡張末期容積Ｖ_edと等容積拡張開始点IVとを結ぶ線Ｌ_a の傾きであって、圧力容積ループの容積軸方向の幅寸法は左心室の一拍あたりの拍出量ＳＶに相当するから、上記数式５は図７から導かれる。
【００４８】
【数５】
Ｅ_a ＝Ｐ_es／ＳＶ
【００４９】
左心室収縮末期エラスタンス算出手段９６は、上記大動脈実効エラスタンス算出手段９４により算出された大動脈実効エラスタンスＥ_a と前記心機械効率算出手段８８により算出された心機械効率Ｅ_a ／Ｅ_esとに基づいて左心室収縮末期エラスタンスＥ_esを算出する。すなわち、大動脈実効エラスタンスＥ_a を心機械効率Ｅ_a ／Ｅ_esで除算することにより左心室収縮末期エラスタンスＥ_esを算出する。
【００５０】
表示制御手段９８は、前記心機械効率算出手段８８により逐次算出された前駆出期間ＰＥＰと駆出期間ＬＶＥＴとの比ＰＥＰ／ＬＶＥＴすなわち心機械効率Ｅ_a ／Ｅ_es、および左心室収縮末期エラスタンス算出手段９６により逐次算出された左心室収縮末期エラスタンスＥ_esを、たとえば図１０に示すように、共通の時間軸に沿ったトレンドグラフ形式で表示器３２に表示させる。
【００５１】
図１１は、前記演算制御装置２８の制御作動の要部を説明するフローチャートである。図１１のステップ（以下、ステップを省略する）ＳＡ１では、心電信号ＳＥにより表される心電誘導波形のＱ波が発生したか否かが判断される。このＳＡ１の判断が否定された場合には本ルーチンが終了させられて繰り返される。しかし、上記ＳＡ１の判断が肯定された場合には、ＳＡ２において、第１心音I の終端が発生したか否かが心音信号ＳＳに基づいて判断される。このＳＡ２の判断が否定された場合には繰り返しＳＡ２の判断が実行されるが、肯定された場合には、ＳＡ３において、上記Ｑ波の発生時から第１心音I の終端までの前駆出期間ＰＥＰが算出される。本実施例では、上記ＳＡ１乃至ＳＡ３が前駆出期間決定手段８４に対応している。
【００５２】
続くＳＡ４では、第２心音IIが発生したか否かが心音信号ＳＳに基づいて判断される。第２心音IIは、左心室内の圧力が大動脈圧以下になり、大動脈圧弁が閉鎖する時に発生する。従って、第２心音IIの開始は左心室の収縮の終了すなわち収縮末期を意味する。このＳＡ４の判断が否定された場合には繰り返しＳＡ４の判断が実行されるが、肯定された場合には、ＳＡ５において、ＳＡ２において検出された第１心音I の終端点からＳＡ４において検出された第２心音IIの始まりまでの時間が、左心室から血液が駆出される駆出期間ＬＶＥＴとして決定される。本実施例では、上記ＳＡ２、ＳＡ４およびＳＡ５が駆出期間決定手段８６に対応している。
【００５３】
次いで、前記心機械効率算出手段８８に対応するＳＡ６では、数式１に示す予め設定された関係から上記前駆出期間ＰＥＰおよび駆出期間ＬＶＥＴに基づいて心機械効率Ｅ_a ／Ｅ_esが算出され、その数値が表示器３２において表示されるとともに、その心機械効率Ｅ_a ／Ｅ_esの時間的変化を示すトレンドグラフが図１０に示すように表示器３２において表示される。
【００５４】
続いて、前記大動脈実効エラスタンス算出手段９４に対応するＳＡ７において、たとえば前記数式５示す予め設定された関係から、左心室収縮末期大動脈圧Ｐ_esと一拍あたりの拍出量ＳＶとに基づいて大動脈実効エラスタンスＥ_a が算出される。これら収縮末期大動脈圧Ｐ_esおよび拍出量ＳＶは、たとえば図１２に示すような比較的短い周期で繰り返し実行されるルーチンにより逐次算出され、更新されている。
【００５５】
図１２において、ＳＢ１では、カフ１０によるキャリブレーション周期であるか否かが判断される。このＳＢ１の判断が否定された場合はＳＢ４の動脈圧波形推定が実行されるが、肯定された場合には、前記血圧測定手段７６に対応するＳＢ２においてカフ１０を用いた血圧測定がオシロメトリック法或いはコロトコフ音法により実行され、前記関係決定手段７８に対応するＳＢ３では、圧脈波センサ４６により検出される圧脈波の大きさとカフ１０を用いて測定された血圧値との関係を示す図２の対応関係が決定される。次いで、動脈圧波形推定手段８０に対応するＳＢ４において、上記対応関係を用いて圧脈波センサ４６により検出される圧波形が、図４に示すような血圧値の絶対値を表す推定動脈圧波形ＢＰ(t) に変換されてから出力される。
【００５６】
続くＳＢ５では、第１心音I の終端が発生したか否かが心音信号ＳＳに基づいて判断される。このＳＢ５の判断が否定された場合にはＳＢ４以下が繰り返されるが、肯定された場合には、続くＳＢ６において、圧脈波センサ４６から得られる圧脈波信号ＳＭ₂ に基づいて、推定動脈圧波形ＢＰ(t) の立ち上がり点が検出されたか否かが判断される。このＳＢ６の判断が否定された場合にはＳＢ４以下が繰り返される。
【００５７】
しかし、上記ＳＢ６の判断が肯定された場合には、続く時間差算出手段８２に対応するＳＢ７において、ＳＢ５において検出された第１心音I の終端点からＳＢ６において検出された圧脈波の立ち上がり点までの時間差ＴＤを算出する。この時間差ＴＤは、心臓の左心室から駆出された血液が圧脈波センサ４６が装着されている撓骨動脈５６まで伝播するのに必要な伝播時間を表している。
【００５８】
続くＳＢ８では、第２心音IIが発生したか否かが心音信号ＳＳに基づいて判断される。このＳＢ８の判断が否定された場合は本ルーチンが終了させられるが、肯定された場合は、前記収縮末期大動脈圧決定手段９０に対応するＳＢ９において、上記第２心音II発生時から、ＳＢ７において算出された時間差ＴＤだけ後の時間における推定動脈圧波形ＢＰ(t) の大きさすなわち血圧値を収縮末期大動脈圧Ｐ_esとして決定する。次いで、ＳＢ１０において、１脈波分すなわち１周期分の推定動脈圧波形ＢＰ(t) が発生したか否かが判断される。このＳＢ１０の判断が否定された場合は本ルーチンが終了させられるが、肯定された場合は、前記拍出量推定手段９２に対応するＳＢ１１において、前記数式４に示す予め設定された関係から実際の推定動脈圧波形ＢＰ(t) に基づいて、左心室の一拍あたりの拍出量ＳＶが算出される。
【００５９】
図１１に戻って、前記左心室収縮末期エラスタンス算出手段９６に対応するＳＡ８において、前記ＳＡ６において求められた心機械効率Ｅ_a ／Ｅ_esと前記ＳＡ７において求められた大動脈実効エラスタンスＥ_a とに基づいて、左心室収縮末期エラスタンスＥ_esが算出され、その値が表示器３２において表示されるとともに、その値の変化を示すトレンドグラフが図１０に示すように表示器３２において表示される。なお、上記ＳＡ６およびＳＡ８は、心機械効率Ｅ_a ／Ｅ_es、および左心室収縮末期エラスタンスＥ_esを、表示器３２において所定の時間軸に沿って逐次表示する表示制御手段９８に対応している。
【００６０】
上述のように、本実施例によれば、図７に示すように、一拍毎に描かれる圧容積ル−プを容積軸に平行な２辺である収縮期等圧力線および拡張期等圧力線と圧力軸に平行な２辺である収縮期等容積線および拡張期等容積線とから成る矩形に近似したとき、前記大動脈実効エラスタンスＥ_a と左心室収縮末期エラスタンスＥ_esとの比すなわち心機械効率Ｅ_a ／Ｅ_esを、心臓の前駆出時間ＰＥＰと駆出時間ＬＶＥＴとの比ＰＥＰ／ＬＶＥＴで近似できるという事実から、心機械効率算出手段８８（ＳＡ６）により、数式１に示す予め設定された関係から前駆出期間決定手段８４（ＳＡ３）により１拍毎に求められた前駆出期間ＰＥＰおよび駆出期間決定手段８６（ＳＡ５）により１拍毎に求められた駆出期間ＬＶＥＴに基づいて心機械効率Ｅ_a ／Ｅ_esが算出されるので、心機能を非侵襲で簡便に監視できる。
【００６１】
また、本実施例によれば、左心室収縮末期エラスタンス算出手段９６（ＳＡ８）により、大動脈実効エラスタンス算出手段９４（ＳＡ７）により算出された大動脈実効エラスタンスＥ_a と前記心機械効率算出手段８８（ＳＡ６）により算出された心機械効率Ｅ_a ／Ｅ_esとに基づいて左心室収縮末期エラスタンスＥ_esが算出されるので、心機能に対応する左心室収縮末期エラスタンスＥ_esを非侵襲で簡便に測定できる。
【００６２】
また、本実施例によれば、前記心音マイクロホン６２は、前記生体の食道などの体腔内において心臓の近傍に配置され、その生体の心臓からから発生する第１心音I および第２心音IIを検出するものであり、前記前駆出期間決定手段８４（ＳＡ３）は、心電誘導装置６８から得られた心電誘導波形のＱ波から上記第１心音I 末期までの時間を上記前駆出期間ＰＥＰとしてを算出するものであるので、非侵襲で前駆出時間ＰＥＰが正確に測定される利点がある。
【００６３】
また、本実施例によれば、前記駆出期間決定手段８６（ＳＡ５）は、心音検出装置６８から得られた第１心音I の末期から第２心音IIの発生時までの区間を駆出期間ＬＶＥＴを直接的に算出するものであるか、或いは、心電誘導装置６８から得られた心電誘導波形のＱ波から前記第２心音IIまでの区間（ＰＥＰ＋ＬＶＥＴ）から上記前駆出時間ＰＥＰを差し引くことにより駆出期間ＬＶＥＴを算出するものであるか、また或いは、前記推定動脈圧波形ＢＰ(t) の立ち上がり点から大動脈弁閉鎖を示すノッチまでの時間から求められるので、駆出期間ＬＶＥＴを非侵襲で正確に算出できる利点がある。
【００６４】
また、本実施例において、前記心機能監視装置８は、心機械効率算出手段８８（ＳＡ６）により逐次算出された前駆出期間ＰＥＰと駆出期間ＬＶＥＴとの比ＰＥＰ／ＬＶＥＴすなわち心機械効率Ｅ_a ／Ｅ_es、および左心室収縮末期エラスタンス算出手段９６（ＳＡ８）により算出された左心室収縮末期エラスタンスＥ_esを、表示器３２において所定の時間軸に沿って逐次表示する表示制御手段９８を備えているので、たとえば手術中に患者の心機能が低下しつつある場合などにおいて、その心機械効率Ｅ_a ／Ｅ_esおよび左心室収縮末期エラスタンスＥ_esのトレンドより心機能の変化傾向を正確に知ることができるので、異常値に達する前に心機能の異常を予知することができる利点がある。
【００６５】
また、本実施例において、前記拍出量推定手段９２（ＳＢ１１）は、動脈圧波形推定手段８０（ＳＢ４）により推定さた推定動脈圧波形ＢＰ(t) に基づいて拍出量ＳＶを算出するものであるので、インピーダンス測定用電極やインピーダンス測定回路、超音波映像発生装置など、拍出量ＳＶを検出するための検出装置を増設することなく拍出量ＳＶが得られる利点がある。
【００６６】
以上、本発明の一実施例を図面に基づいて説明したが、本発明はその他の態様においても適用される。
【００６７】
たとえば、前述の実施例の心機能監視装置８では、心機械効率Ｅ_a ／Ｅ_esおよび左心室収縮末期エラスタンスＥ_esが算出されて表示されるように構成されていたが、それら心機械効率Ｅ_a ／Ｅ_esおよび左心室収縮末期エラスタンスＥ_esの一方のみが算出され或いは表示されるものであっても差し支えない。
【００６８】
また、前述の収縮末期大動脈圧決定手段９０において、収縮末期大動脈圧Ｐ_esは、第２心音IIの開始時点から時間差ＴＤだけ経過した時点における推定動脈圧波形ＢＰ（ｔ）の大きさとして決定されていたが、収縮末期大動脈圧Ｐ_esは経験則により平均血圧値（平均動脈圧）ＭＡＰで近似できるため、推定動脈圧波形ＢＰ（ｔ）から得られる血圧瞬時値の１周期Ｔ当たりの平均値すなわち平均血圧値ＭＡＰを収縮末期大動脈圧Ｐ_esとして決定してもよい。なお、この平均血圧値ＭＡＰは、ΣＢＰ（ｔ）／Ｔとして表されるものであるから、１周期Ｔ当たりの推定動脈圧波形ＢＰ（ｔ）の重心点の圧力値としても表現され得る。
【００６９】
また、前述の拍出量推定手段９２は、数式４から推定動脈圧波形ＢＰ(t) に基づいて１拍当たりの拍出量ＳＶを算出するものであったが、クビセク（Kubicek ）法として知られる予め設定された関係から、頸部と腰部とに装着された電極を用いて検出されるインピーダンスカーディオグラフに基づいて算出されてもよいし、予め設定された関係から超音波を用いて得られる心臓画像の幅寸法に基づいて算出されても差し支えない。なお、１分当たりの心拍出量ＣＯが求められる場合には、その心拍出量ＣＯを心拍数ＨＲで除算することにより上記１拍当たりの拍出量ＳＶが得られる。
【００７０】
なお、上述したのはあくまでも本発明の一実施例であり、本発明はその主旨を逸脱しない範囲において種々変更が加えられ得るものである。
【図面の簡単な説明】
【図１】本発明の一実施例の心機能監視装置の構成の要部を説明するブロック図である。
【図２】図１の心機能監視装置において圧脈波センサにより検出された圧脈波から動脈圧波形を推定するために用いられる対応関係を示すである。
【図３】図１の心機能監視装置の演算制御装置の制御機能の要部を説明する機能ブロック線図である。
【図４】図３の動脈圧波形推定手段により推定された動脈圧波形の例を示す図である。
【図５】図３の前駆出期間決定手段および駆出期間決定手段により決定される前駆出期間ＰＥＰおよび駆出期間ＬＶＥＴと、大動脈圧波形、心電誘導波形、および心音との関係を説明するタイムチャートである。
【図６】生体の左心室内の容積と圧力との関係の例を１拍のループで示す図である。
【図７】図６のような圧容積ループを矩形に近似した図、およびその図と左心室収縮末期エラスタンスＥ_es、大動脈実効エラスタンスＥ_a などとの関係を説明する図である。
【図８】種々の圧容積ループと収縮末期圧−容積関係線Ｌ_esとの関係を説明する図である。
【図９】左心室収縮時間と左心室エラスタンスとの関係を説明する図である。
【図１０】図１の心機能監視装置において、心機械効率Ｅ_a ／Ｅ_esおよび左心室収縮末期エラスタンスＥ_esが表示器に表示されるトレンドグラフの例を示す図である。
【図１１】図１の心機能監視装置の演算制御装置の制御作動の要部を説明するフローチャートであって、メインルーチンを示す図である。
【図１２】図１の心機能監視装置の演算制御装置の制御作動の要部を説明するフローチャートであって、推定動脈圧波形、収縮末期大動脈圧、拍出量算出ルーチンを示す図である。
【符号の説明】
６２：心音マイクロホン（心音検出装置）
６８：心電誘導装置
８０：動脈圧波形推定手段
８４：前駆出期間決定手段
８６：駆出期間決定手段
８８：心機械効率算出手段
９０：収縮末期大動脈圧決定手段
９２：拍出量推定手段
９４：大動脈実効エラスタンス算出手段
９６：左心室収縮末期エラスタンス算出手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a heart that evaluates the function of the heart of a living body by continuously calculating the cardiac mechanical efficiency, which is the mechanical efficiency of the living heart, and the maximum pressure-volume ratio indicating the degree of the cardiac output function. The present invention relates to a function monitoring device.
[0002]
[Prior art]
The characteristic of the left ventricle as the elastic chamber at the end systole, that is, the elastic modulus is determined as the left ventricular end systole (when the aortic valve is closed) elastance E_esThe characteristic as an effective elastic cavity of the aorta, that is, the elastic modulus is expressed as the effective aortic elastance E_aThis aortic effective elastance E when defined as_aAnd left ventricular end systolic elastance E_esRatio E_a/ E_esRepresents the left ventricular-aortic coupling balance, ie, the mechanical efficiency of the left ventricle, and the left ventricular end systolic elastance E_esAlso represent the left ventricular blood pumping ability alone,_a/ E_esOr E_esIs important as an index of cardiac function, and changes uniformly according to cardiac function such as rest, stress, and heart failure, and also improves cardiac metabolic efficiency (cardiac work / cardiac oxygen consumption) Reflection has become clear theoretically and experimentally.
[0003]
[Problems to be solved by the invention]
However, the left ventricular end systolic elastance E, known as the maximum pressure-volume ratio or the left ventricular end-systolic pressure-volume ratio._esContinuously detects changes in the relationship between the left ventricular pressure and volume, and the pressure volume drawn in two-dimensional coordinates of the volume axis indicating the volume value in the left ventricle and the pressure axis indicating the pressure value in the left ventricle In the figure, a left and right ventricular unstressed volume V, which is a volume when the internal pressure is zero, is obtained while obtaining a pressure volume loop of cardiac output that varies depending on the preload or afterload of the myocardium.₀ Is estimated from a plurality of pressure volume loops, and the end systolic pressure P_esThe end systolic capacity V_esAnd left ventricular unstressed volume V₀ Difference from (V_es-V₀ ) Divided by). Therefore, since the internal pressure and volume of the left ventricle must be measured at the same time, the conventional method for determining the internal pressure and volume of the left ventricle openly requires open surgery and insertion of a catheter. Monitoring of cardiac function was very difficult. Aorta effective elastance E_aIn the above-described pressure-volume diagram, a pressure-volume loop of cardiac output that varies depending on the preload or afterload of the myocardium is obtained, and the end systolic pressure P_esThe end expansion capacity V_edAnd end systolic capacity V_esDifference from (V_ed-V_es), It is very difficult to monitor the cardiac function with the conventional method in which the internal pressure and volume of the left ventricle are invasively determined.
[0004]
The present invention has been made against the background of the above circumstances, and the object of the present invention is the efficiency of the heart machine E_a/ E_esOr left ventricular end systolic elastance E_esIt is an object of the present invention to provide a cardiac function monitoring device capable of continuously and simply monitoring non-invasively.
[0005]
Based on the above circumstances, the present inventors have conducted various studies on the electrocardiogram, radial artery pressure waveform, phonocardiogram, and pulmonary artery catheter data of a living body. Of the four sides constituting the rectangular pressure volume loop, the isobaric expansion line, the isobaric expansion line, the isobaric contraction line, the isobaric contraction line, the isobaric contraction line and the isobaric expansion When a line is approximated to a perfect rectangle with two sides parallel to the volume axis and an isovolumetric contraction line and an isovolumetric extension line parallel to the pressure axis, the aorta effective elastance E_aAnd left ventricular end systolic elastance E_esRatio, ie, heart machine efficiency E_a/ E_esIs the ratio PEP between the cardiac precursor ejection time PEP and the ejection time LVET on the assumption that the pressure volume ratio E at each point of the pressure volume loop is a linear function E (t) = k · t of time. I found the fact that it can be approximated with / LVET. The present invention has been made based on such findings.
[0006]
[Means for Solving the Problems]
  That is, the gist of the present invention is a cardiac function monitoring device for monitoring the function of the heart of a living body based on cardiac mechanical efficiency, and (a) from the start of contraction of the left ventricle of the living body,ThatA precursor period determining means for non-invasively determining a precursor period until blood is ejected from the left ventricle; (b)A section from the end of the first heart sound to the time of occurrence of the second heart sound included in the heart sound of the living body,Ejection period in which blood is ejected from the left ventricle of the living bodyAsA non-invasive ejection period determining means; and (c) a cardiac machine efficiency calculating means for calculating the cardiac mechanical efficiency of the living body based on the precursor ejection period and the ejection period from a preset relationship. ,(D) an aortic pressure estimating means for estimating the aortic pressure of the living body; and (e) an end-systolic aortic pressure for determining an aortic internal pressure at the end systolic stage of the living body based on the aortic pressure estimated by the aortic pressure estimating means. Determining means; (f) stroke volume estimating means for noninvasively estimating the stroke volume per beat of the left ventricle of the living body; and (g) determining the end systolic aortic pressure from a preset relationship. The aortic effective elastance is calculated based on the intra-aortic pressure at the end systole of the left ventricle determined by the means and the stroke volume per beat of the left ventricle estimated by the stroke volume estimating means. A left ventricle based on the stance calculating means, and (h) the aortic effective elastance calculated by the aorta effective elastance calculating means and the cardiac mechanical efficiency calculated by the cardiac mechanical efficiency calculating means. And left ventricular end-systolic elastance calculating means for calculating a reduced end elastanceIs to include.
[0007]
【The invention's effect】
  According to this configuration, the aorta effective elastance E based on the pre-ejection period and ejection period determined non-invasively from a preset relationship in the cardiac machine efficiency calculation means._a And left ventricular end systolic elastance E_esEfficient cardiac mechanical efficiency corresponding to cardiac function_a / E_esCan be measured easily and non-invasively.Further, the aorta effective elastance E calculated by the aorta effective elastance calculation means by the left ventricular end systolic elastance calculation means. _a And the heart machine efficiency E calculated by the heart machine efficiency calculation means _a / E _es Based on the left ventricular end systolic elastance E _es Is calculated so that left ventricular end systolic elastance E corresponding to cardiac function _es Can be measured non-invasively and easily. Furthermore, since the interval from the end of the first heart sound to the time of the second heart sound is directly determined as the ejection period LVET, the ejection period LVET is calculated noninvasively and accurately.
[0008]
Other aspects of the invention
Here, preferably, the preset relationship is as shown in Equation 1.
[0009]
[Expression 1]
E_a/ E_es= PEP / LVET
[0010]
This mathematical formula 1 represents the pressure volume loop drawn at every beat in the pressure volume diagram, and the two sides parallel to the pressure axis and the systolic pressure line and the diastolic pressure line parallel to the volume axis. The aorta effective elastance E is approximated to a rectangle composed of a systolic isovolume and a diastole isovolume._aAnd left ventricular end systolic elastance E_esRatio, ie, heart machine efficiency E_a/ E_esCan be approximated by the ratio PEP / LVET of the cardiac precursor ejection time PEP and ejection time LVET.
[0012]
Preferably, the cardiac function monitoring device detects an electrocardiographic induction waveform of the living body through an electrode in contact with the living body, and a heart sound generated from the living body attached to the living body. The heart sound detecting device is arranged in the vicinity of the heart in a body cavity such as the esophagus of the living body, and the first heart sound I and the second sound generated from the heart of the living body. Heart sound II is detected.
[0013]
Preferably, the pre-determining period determining means determines the time from the start of contraction of the heart to the time from the Q wave of the electrocardiographic induction waveform obtained from the electrocardiographic induction device to the end of the first heart 1 sound. Is calculated as the precursor discharge time PEP until the ink is actually discharged. In this way, there is an advantage that the precursor period PEP is accurately measured non-invasively.
[0015]
Preferably, the cardiac function monitoring device is configured such that a ratio PEP / LVET between the precursor ejection period PEP and the ejection period LVET sequentially calculated by the cardiac machine efficiency calculation means, that is, cardiac machine efficiency E_a/ E_esAnd / or left ventricular end systolic elastance calculated by the left ventricular end systolic elastance calculating means_esThe display further includes display control means for sequentially displaying the data along a predetermined time axis on the display. In this way, the heart machine efficiency E is improved by the display control means._a/ E_esAnd left ventricular end systolic elastance E_esAre sequentially displayed on the display, for example, when the cardiac function of the patient is decreasing during the operation, the cardiac mechanical efficiency E_a/ E_esOr left ventricular end systolic elastance E_esSince the trend of change in cardiac function can be known from the trend, there is an advantage that abnormal cardiac function can be predicted before reaching an abnormal state.
[0016]
Preferably, the stroke volume estimating means calculates a stroke volume SV based on the waveform of the aortic pressure estimated by the aortic pressure estimating means. In this way, there is an advantage that the stroke volume SV can be obtained without adding a detection device for detecting biological information.
[0017]
Preferably, the end systolic aortic pressure determining means detects an average blood pressure MAP obtained from the estimated aortic pressure, an end point of a T wave of the electrocardiogram-induced waveform, or a start point of the second heart sound II. The estimated aortic pressure corresponding to the aortic pressure at the time point is determined as the end systolic aortic pressure P_esIs to be determined. In this way, non-invasive and end systolic aortic pressure P_esHas the advantage of being accurately determined.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram illustrating the configuration of a cardiac function monitoring apparatus 8 to which the present invention is applied.
[0019]
In FIG. 1, reference numeral 10 denotes a cuff having a rubber bag in a cloth belt-like bag, which is mounted in a state of being wound around the upper arm 12 of a patient, for example. A pressure sensor 14, an exhaust control valve 16, and an air pump 18 are connected to the cuff 10 via a pipe 20. The exhaust control valve 16 includes a pressure supply state that allows supply of pressure into the cuff 10, a slow exhaust pressure state that gradually exhausts the inside of the cuff 10, and a rapid exhaust pressure state that rapidly exhausts the inside of the cuff 10. It is configured to be switched to one state.
[0020]
The pressure sensor 14 detects the pressure in the cuff 10 and supplies a pressure signal SP representing the pressure to the static pressure discrimination circuit 22 and the pulse wave discrimination circuit 24, respectively. The static pressure discriminating circuit 22 includes a low-pass filter, discriminates the cuff pressure signal SK representing the steady pressure included in the pressure signal SP, and calculates the cuff pressure signal SK via the A / D converter 26. 28. The pulse wave discrimination circuit 24 includes a bandpass filter, and a pulse wave signal SM that is a vibration component of the pressure signal SP.₁ And the pulse wave signal SM₁ Is supplied to the arithmetic and control unit 28 via the A / D converter 30. This pulse wave signal SM₁ The cuff pulse wave represented by is a pressure vibration wave generated from a brachial artery (not shown) and transmitted to the cuff 10 in synchronization with the heartbeat of the patient, and the pulse wave discrimination circuit 24 functions as a cuff pulse wave detection means. Yes.
[0021]
The arithmetic control unit 28 includes a CPU 29, a ROM 31, a RAM 33, and a so-called microcomputer having an I / O port (not shown). The CPU 29 has a storage function of the RAM 33 according to a program stored in advance in the ROM 31. By executing the signal processing while using it, a drive signal is output from the I / O port to control the exhaust control valve 16 and the air pump 18 via a drive circuit (not shown). When measuring blood pressure using the cuff 10, for example, the pressure in the cuff 10 is rapidly increased to a predetermined target pressure, then gradually decreased at a rate of about 3 mmHg / sec, and pulses sequentially collected in the process of gradually decreasing the pressure. Wave signal SM₁ The blood pressure values (reference blood pressure values) such as the maximum blood pressure value and the minimum blood pressure value are determined by the oscillometric method based on the change of the pulse wave represented by the above, and the determined blood pressure value is displayed on the display 32.
[0022]
The pressure pulse wave detection probe 34 is screwed into an outer case (not shown) that accommodates a container-shaped sensor housing 36 and the sensor housing 36 to move the sensor housing 36 in the width direction of the radial artery 56, And a screw shaft 41 that is rotationally driven by a motor (not shown). A mounting band is attached to the outer case, and the side where the cuff 10 is not wound by the mounting band in a state where the opening end of the container-shaped sensor housing 36 faces the body surface 38 of the human body, for example, the left side It is designed to be detachably attached to the wrist.
[0023]
A pressure pulse wave sensor 46 is provided inside the sensor housing 36 through a diaphragm 44 so as to be relatively movable and projectable from the opening end of the sensor housing 36. The pressure is applied by the sensor housing 36, the diaphragm 44, and the like. A chamber 48 is formed. Pressure air is supplied from the air pump 50 through the pressure regulating valve 52 into the pressure chamber 48, so that the pressure pulse wave sensor 46 has a pressing force corresponding to the pressure in the pressure chamber 48. Pressed against the body surface 38. In this embodiment, the pressing force of the pressure pulse wave sensor 46 is indicated by the pressure in the pressure chamber 48 (unit: mmHg).
[0024]
The sensor housing 36 and the diaphragm 44 constitute a pressing device 58 that presses the pressure pulse wave sensor 46 toward the radial artery 56. The screw pulse 41 and the motor (not shown) are pressed by the pressure pulse wave sensor 46. A pressing position changing device that changes the pressing position by moving it in the width direction of the radial artery 56, that is, a width direction moving device is configured.
[0025]
The pressure pulse wave sensor 46 includes a plurality of semiconductor pressure sensitive elements (not shown) on the flat pressing surface 54 made of a semiconductor chip made of single crystal silicon or the like, and the width direction of the radial artery 56, that is, the screw shaft 41. The parallel pressure pulse wave sensors 46 are arranged at a constant interval of about 0.2 mm in the moving direction, and are pressed onto the radial artery 56 on the body surface 38 of the wrist 42, whereby the radial artery A pressure oscillation wave, that is, a pressure pulse wave generated from 56 and transmitted to the body surface 38 is detected, and a pressure pulse wave signal SM representing the pressure pulse wave is detected.₂ Is supplied to the arithmetic and control unit 28 via the A / D converter 58.
[0026]
The CPU 29 of the arithmetic control device 28 executes input processing using the storage function of the RAM 33 in accordance with a program stored in the ROM 31 in advance, and outputs a drive signal to the air pump 50 and the pressure regulating valve 52 via a drive circuit (not shown). The pressure in the pressure chamber 48 is adjusted. For example, when monitoring the continuous blood pressure, the arithmetic and control unit 28 makes a part of the vascular wall of the radial artery 56 substantially flat based on the pressure pulse wave successively obtained in the slow pressure change process in the pressure chamber 48. Optimal pressing force P of the pressure pulse wave sensor 46_HDPOAnd the optimum pressing force P is determined._HDPOThe pressure regulating valve 52 is controlled so as to maintain the above.
[0027]
Further, the arithmetic and control unit 28 uses the cuff 10 to measure the systolic blood pressure value BP._SYSAnd minimum blood pressure BP_DIAAnd the above optimum pressing force P_HDPOThe maximum value P of the pressure pulse wave detected by the central position pressure detection element (active element) located directly above the radial artery 56 among the semiconductor pressure sensitive elements of the pressure pulse wave sensor 46 in a state where the pressure is maintained._MmaxAnd minimum value P_MminBased on the measured blood pressure value BP and the pressure pulse wave magnitude P_MA correspondence relationship between the absolute value and the magnitude P of the pressure pulse wave successively detected by the pressure pulse wave sensor 46 is obtained from the correspondence relationship._M(MmHg), that is, maximum value (upper peak value) P_MmaxAnd lowest value (lower peak value) P_MminBlood pressure MBP based on_SYSAnd minimum blood pressure MBP_DIA(Estimated blood pressure value, ie, monitored blood pressure value) is sequentially determined, and the determined maximum blood pressure value MBP is displayed on the display 32._SYSAnd minimum blood pressure MBP_DIAAre numerically displayed for each beat, and an estimated arterial pressure waveform BP (t) indicating the estimated blood pressure value MBP is continuously output.
[0028]
The correspondence relationship is as shown in FIG. In Equation 2, A is a constant indicating the slope, and B is a constant indicating the intercept.
[0029]
[Expression 2]
MBP = AP_M+ B
[0030]
In FIG. 1, a heart sound microphone 62 that functions as a heart sound detection device is disposed in the vicinity of the heart of a living body, detects a heart sound generated from the heart, and outputs a heart sound signal SS representing the heart sound. The heart sound microphone 62 may be attached to the body surface of the living body, but it is better if it is placed in a body cavity such as the esophagus of the living body in order to detect the heart sound more clearly by bringing it closer to the heart. The heart sound signal SS output from the heart sound microphone 62 is supplied to the arithmetic and control unit 28 via an amplifier (not shown), a band filter 64 for noise removal, and an A / D converter 66. As shown in FIG. 5, the heart sounds include the first heart sound I corresponding to the closing of the mitral valve and the opening of the aortic valve, the second heart sound II corresponding to the closing of the aortic valve, and the like.
[0031]
The electrocardiographic induction device 68 includes a plurality of electrodes 70 attached to a part of the living body's epidermis that is positioned so as to sandwich the living body's heart, and an electrocardiographic induction waveform, that is, an ECG waveform that is induced in the epidermis of the living body , And an electrocardiographic induction signal SE representing the electrocardiographic induction waveform is output to the arithmetic and control unit 28. For example, as shown in FIG. 5, well-known P waves, Q waves, R waves, S waves, and T waves are sequentially included in one cycle of the electrocardiographic induction waveform.
[0032]
The arithmetic and control unit 28 further processes the electrocardiographic induction signal SE, the heart sound signal SS, and the arterial pressure wave to produce a cardiac machine efficiency E_a/ E_esAorta effective elastance E_aLeft ventricular end systolic elastance E_esIs calculated and stored in a storage device (not shown) such as a hard disk, a semiconductor memory card, or a magnetic tape, and the above-mentioned cardiac mechanical efficiency E is calculated in the display 32 or a printer (not shown)._a/ E_esAnd left ventricular end systolic elastance E_esDisplay the trend.
[0033]
FIG. 3 is a functional block diagram for explaining the main part of the control function of the arithmetic and control unit 28. In FIG. 3, when the blood pressure is measured, the compression pressure of the cuff 10 that is changed by the cuff pressure control means 74 is detected by the pressure sensor 14. The blood pressure measuring means 76 is an oscillometric method or a Korotkoff based on a pulse synchronization signal obtained in the process of gradually changing the pressure applied by the cuff 10 at a speed of about 2 to 3 mmHg / sec, for example, a change in pulse wave amplitude or Korotkoff sound. Maximum blood pressure BP of the living body according to the sound method_SYS, Mean blood pressure BP_MEAN, And diastolic blood pressure BP_DIA(Reference blood pressure value) is measured.
[0034]
The relationship determining means 78 is a pressure detected by a central position pressure detecting element (active element) located directly above the radial artery 56 among the plurality of pressure detecting elements arranged on the pressing surface 54 of the pressure pulse wave sensor 46. Pulse wave size P_MAnd the blood pressure value BP measured by the blood pressure value measuring means 70 are determined in advance as shown in FIG. 2, for example.
[0035]
The estimated blood pressure value determining means, that is, the arterial pressure waveform estimating means 80 is detected by, for example, the active element among the plurality of pressure detecting elements arranged on the pressing surface 54 of the pressure pulse wave sensor 46 from the correspondence relationship of FIG. The estimated blood pressure value MBP of the living body is continuously determined based on the magnitude of the pressure pulse wave, and an estimated arterial pressure waveform BP (t) as shown in FIG. 4 is output, for example. The estimated arterial pressure waveform BP (t) represents the brachial artery pressure waveform, but corresponds to the aortic pressure waveform. Therefore, the arterial pressure waveform estimating means 80 functions as an aortic pressure estimating means, and the estimated arterial pressure waveform BP (t) means the estimated aortic pressure. If there is a difference that causes a problem in measurement between the brachial artery pressure waveform and the aortic pressure waveform, the aortic pressure waveform is calculated from the brachial artery pressure waveform using a previously determined transfer function. Also good.
[0036]
The time difference calculating means 82 calculates a time difference TD between the end of the first heart sound I obtained by the heart sound microphone 62 and the rising point of the pressure pulse wave obtained by the pressure pulse wave sensor 46. Since the end of the first heart sound I is detected when blood ejection starts from the left ventricle of the heart to the aorta, this time difference TD is a radial artery in which the aortic pressure is attached to the pressure pulse wave sensor 46. The propagation time to propagate to 56 is meant.
[0037]
The precursor discharge period determining means 84 noninvasively determines the precursor discharge period PEP from the start of contraction of the myocardium in the left ventricle of the living body until blood is ejected from the left ventricle. For example, the time from the generation of the Q wave of the electrocardiogram waveform to the end of the first heart sound I is measured by counting the reference clock pulse, etc., and the precursor emission period PEP (seconds) is determined for each beat. To do. Alternatively, it is calculated by subtracting the time difference TD calculated by the time difference calculating means 82 from the time from the generation time of the Q wave of the electrocardiogram-induced waveform to the rising point of the aortic pressure waveform estimated by the arterial pressure waveform estimating means 80. May be. As shown in the time chart of FIG. 5, the precursor discharge period PEP is the time from the start of cardiac contraction to the time when blood is actually pumped (the aortic valve is opened) from the left ventricle.
[0038]
The ejection period determination means 86 non-invasively determines the ejection period LVET in which blood is ejected from the left ventricle of the living body. For example, the time from the end point of the first heart sound I to the start point of the second heart sound II is measured by, for example, using a reference clock pulse as a coefficient, and the ejection period LVET (seconds) is determined. Alternatively, by measuring the time from the occurrence of the Q wave of the electrocardiogram-induced waveform to the start point of the second heart sound II, the total value of the cardiac contraction period, that is, the pre-ejection period PEP and the ejection period LVET (PEP + LVET) And the ejection period LVET (seconds) may be calculated for each beat by subtracting the precursor ejection period PEP obtained by the precursor ejection period determining means 84 from the total value (PEP + LVET). Alternatively, the time from the rising point of the estimated arterial pressure waveform BP (t) to the notch indicating the aortic valve closure (t in FIG. 4).₂ To t_Four ) May be calculated to calculate the ejection period LVET (seconds).
[0039]
Based on the preset relationship shown in the mathematical formula 1, the heart machine efficiency calculating means 88 is calculated for each beat by the precursor ejection period PEP and the ejection period determining means 86 determined for each beat by the precursor ejection period determining means 84. Based on the required ejection period LVET, the effective aortic elastance E_aAnd left ventricular end systolic elastance E_esRatio, ie, heart machine efficiency E_a/ E_esAnd is output for every beat or as a moving average value within a preset section of about 5 beats. The cardiac mechanical efficiency calculation means 88 calculates E based on the above-described precursor ejection period PEP and the total value (PEP + LVET) of the precursor ejection period PEP and ejection period LVET from the preset relationship shown in Equation 3._i/ E_esAnd the E_i/ E_esAnd machine efficiency E_a/ E_esThe machine efficiency E_a/ E_esMay be calculated.
[0040]
[Equation 3]
E_i/ E_es= PEP / (PEP + LVET)
[0041]
Here, the relationship between the volume V and the pressure P in the left ventricle of the living heart is shown in a pressure volume diagram of two-dimensional coordinates of a pressure axis and a volume axis as shown in FIG. 6, for example. The pressure volume loop of FIG. 6 drawn for each cycle of the heart is represented by an isovolumetric extension line L₁ Isobaric extension line L₂ , Isovolumetric contraction line L_Three , Isobaric contraction line L_Four Since the four sides are substantially rectangular, among these four sides, the isobaric contraction line L_Four And isobaric extension line L₂ Is the two sides parallel to the volume axis, and the isovolumetric contraction line L_Three And isovolumetric extension line L₁ Can be approximated to a complete rectangular pressure volume loop shown in FIG. In FIG. 7, point IV is the end systole, ie, the isovolumetric expansion start point, point I is the isobaric expansion start point, point II is the end diastole, ie, the isovolumetric contraction start point, point III is the isobaric contraction start point, P_esIs the end systolic pressure in the left ventricle, V_edIs the end-diastolic capacity in the left ventricle, V_esIs the end systolic volume in the left ventricle, V_oIs the left ventricular unstressed volume that is the volume in the left ventricle when the internal pressure is substantially zero, and the end-diastolic volume V in the left ventricle_edAnd end systolic volume V in the left ventricle_esDifference from (V_ed-V_es) Corresponds to the stroke volume per stroke (slotalk volume) SV. This left ventricular unstressed volume V_oIs the end systolic pressure P of each pressure volume loop, as shown in FIG._esA line indicating the relationship between (IV point) and volume, that is, end systolic pressure-volume relationship line L_esAnd the intersection of the volume axis.
[0042]
For example, in FIG. 7 showing a pressure volume loop approximated to a rectangle, left ventricular end systolic elastance E_esIs the end systolic pressure-volume relationship line L_esIs the left ventricular end systolic pressure-volume ratio, which indicates the magnitude corresponding to the basic contractile force of the heart, and is an indicator of cardiac function. Here, in FIG. 7, the left ventricular unstressed volume V_oAnd left ventricular end systolic volume V_esThe geometric distance between and the left ventricular end systolic volume V_esAnd left ventricular end-diastolic capacity V_edThe geometric distance between and b, the isovolumetric contraction line L_Three And isovolumetric extension line L₁ Where c is the geometric length, the end systolic pressure-volume relationship line L_esSlope E_esIs represented by c / a. Also, the left ventricular unstressed volume V on the volume axis_oLine L connecting to the isobaric contraction start point III_iSlope E_iIs expressed by c / (a + b), and the end-diastolic volume V on the volume axis_edLine L connecting the same volume expansion start point IV_aSlope of the aorta_aIs represented by c / b. Therefore, E_a/ E_esA / b, E_i/ E_esBecomes a / (a + b).
[0043]
On the other hand, as shown in FIG. 9, the left ventricular elasticity (elastance) E has an equal volumetric contraction period T._iE after_iAnd the total contraction period T_es(= T_i+ T_e) After E_esAssuming that the linear function E (t) = k · t of the left ventricular contraction time t such that_i/ E_es= T_i/ T_esIs established. Also, the isovolumetric contraction period T_iCorresponds to the precursor release period PEP and the total contraction period T_esCorresponds to the added value (PEP + LVET) of the precursor ejection period PEP and the ejection period LVET, so that the above approximate equations 1 and 3 are derived.
[0044]
3 is detected by the estimated arterial pressure waveform BP (t) output from the arterial pressure waveform estimating means 80, the time difference TD obtained by the time difference calculating means 82, and the heart sound microphone 62. The end systolic aortic pressure P, which is the pressure of the aorta at the end systole of the left ventricle_esTo decide. For example, the start sound of the second heart sound II is generated at the end of the closing of the aortic valve, that is, the contraction of the left ventricle, and the aortic pressure at that time is propagated to the radial artery after the time difference TD. The magnitude of the estimated arterial pressure waveform BP (t), that is, the blood pressure value at the time when the time difference TD has elapsed from the determination time is determined as the end systolic aortic pressure P._esDetermine as.
[0045]
The stroke volume estimating means 92 calculates the stroke volume SV (stroke volume) per beat of the left ventricle of the living body from the following formula 4 known as, for example, the Warner & Gardner formula, and the arterial pressure. Estimation is made based on the estimated arterial pressure waveform BP (t) shown in FIG. In the estimated arterial pressure waveform BP (t) shown in FIG.₁ Is the lower peak time t of the estimated arterial pressure waveform BP (t)₂ For example, a time earlier than a predetermined time of about 80 milliseconds, and the ejection period end time t_Four Is the upper peak time t of the estimated arterial pressure waveform BP (t)_Three It is a point of time later than the predetermined time of about 80 milliseconds. Note that K in Equation 4 is a correction constant, and is calibrated in advance with a value obtained directly by, for example, a dilution method (thermodilution method).
[0046]
[Expression 4]

[0047]
The aortic effective elastance calculating means 94 is based on a preset relationship shown in Equation 5, for example, and the end systolic aortic pressure P, which is the pressure of the aorta at the end systole of the left ventricle determined by the end systolic aortic pressure determining means 90._esAnd the aorta effective elastance E based on the stroke volume SV per beat estimated by the stroke volume estimation means 92._aIs calculated. This aortic effective elastance E_aIs the end-diastolic volume V on the volume axis in FIG._edLine L connecting the same volume expansion start point IV_aSince the width dimension in the volume axis direction of the pressure volume loop corresponds to the stroke volume SV per beat of the left ventricle, Equation 5 is derived from FIG.
[0048]
[Equation 5]
E_a= P_es/ SV
[0049]
The left ventricular end systolic elastance calculating means 96 is provided with the aorta effective elastance E calculated by the aorta effective elastance calculating means 94._aAnd the heart machine efficiency E calculated by the heart machine efficiency calculation means 88._a/ E_esBased on the left ventricular end systolic elastance E_esIs calculated. That is, aortic effective elastance E_aThe machine efficiency E_a/ E_esLeft ventricular end systolic elastance E by dividing by_esIs calculated.
[0050]
The display control means 98 is a ratio PEP / LVET between the precursor ejection period PEP and the ejection period LVET sequentially calculated by the cardiac machine efficiency calculating means 88, that is, the cardiac machine efficiency E._a/ E_es, And left ventricular end systolic elastance E sequentially calculated by the left ventricular end systolic elastance calculating means 96_esIs displayed on the display 32 in a trend graph format along a common time axis, for example, as shown in FIG.
[0051]
FIG. 11 is a flowchart for explaining a main part of the control operation of the arithmetic control device 28. In step (hereinafter, step is omitted) SA1 in FIG. 11, it is determined whether or not a Q wave having an electrocardiographic induction waveform represented by the electrocardiographic signal SE has occurred. If the determination at SA1 is negative, this routine is terminated and repeated. However, if the determination in SA1 is affirmed, it is determined in SA2 based on the heart sound signal SS whether or not the end of the first heart sound I has occurred. If the determination of SA2 is denied, the determination of SA2 is repeatedly executed. If the determination is affirmative, in SA3, the precursor emission period PEP from the occurrence of the Q wave to the end of the first heart sound I. Is calculated. In the present embodiment, SA1 to SA3 correspond to the precursor ejection period determining means 84.
[0052]
In SA4, it is determined based on the heart sound signal SS whether or not the second heart sound II has occurred. The second heart sound II is generated when the pressure in the left ventricle falls below the aortic pressure and the aortic pressure valve closes. Therefore, the start of the second heart sound II means the end of the left ventricular contraction, that is, the end systole. If the determination of SA4 is denied, the determination of SA4 is repeatedly executed. If the determination is affirmative, in SA5, the first heartbeat I detected in SA2 from the end point of the first heart sound I detected in SA4. The time until the beginning of 2 heart sounds II is determined as the ejection period LVET in which blood is ejected from the left ventricle. In the present embodiment, SA2, SA4 and SA5 correspond to the ejection period determining means 86.
[0053]
Next, in SA6 corresponding to the heart machine efficiency calculation means 88, the heart machine efficiency E based on the precursor ejection period PEP and the ejection period LVET from the preset relationship shown in Formula 1._a/ E_esAnd the numerical value is displayed on the display 32, and the heart machine efficiency E is calculated._a/ E_esAs shown in FIG. 10, a trend graph showing a change over time is displayed on the display 32.
[0054]
Subsequently, in SA7 corresponding to the aorta effective elastance calculation means 94, for example, the left ventricular end systolic aortic pressure P is determined from the preset relationship shown in the equation 5._esAnd aorta effective elastance E based on stroke volume per beat SV_aIs calculated. These end systolic aortic pressure P_esThe stroke volume SV is sequentially calculated and updated by a routine that is repeatedly executed with a relatively short cycle as shown in FIG. 12, for example.
[0055]
In FIG. 12, in SB1, it is determined whether or not it is a calibration cycle by the cuff 10. If the determination of SB1 is negative, the arterial pressure waveform estimation of SB4 is executed. If the determination is positive, the blood pressure measurement using the cuff 10 is performed in the SB2 corresponding to the blood pressure measurement means 76 by the oscillometric method. Alternatively, a diagram showing the relationship between the magnitude of the pressure pulse wave detected by the pressure pulse wave sensor 46 and the blood pressure value measured using the cuff 10 in the SB3 corresponding to the relationship determining means 78, which is executed by the Korotkoff sound method. Two correspondences are determined. Next, in SB4 corresponding to the arterial pressure waveform estimation means 80, an estimated arterial pressure waveform in which the pressure waveform detected by the pressure pulse wave sensor 46 using the above correspondence relationship represents the absolute value of the blood pressure value as shown in FIG. It is output after being converted to BP (t).
[0056]
In subsequent SB5, whether or not the end of the first heart sound I has occurred is determined based on the heart sound signal SS. If the determination of SB5 is negative, SB4 and subsequent steps are repeated. If the determination is positive, the pressure pulse wave signal SM obtained from the pressure pulse wave sensor 46 is subsequently determined in SB6.₂ Based on the above, it is determined whether or not the rising point of the estimated arterial pressure waveform BP (t) has been detected. If the determination at SB6 is negative, SB4 and subsequent steps are repeated.
[0057]
However, if the determination of SB6 is affirmed, in the SB7 corresponding to the subsequent time difference calculating means 82, from the end point of the first heart sound I detected in SB5 to the rising point of the pressure pulse wave detected in SB6 The time difference TD is calculated. This time difference TD represents a propagation time required for blood ejected from the left ventricle of the heart to propagate to the radial artery 56 to which the pressure pulse wave sensor 46 is attached.
[0058]
In subsequent SB8, it is determined based on the heart sound signal SS whether or not the second heart sound II has occurred. If the determination at SB8 is negative, this routine is terminated. If the determination is affirmative, at SB9 corresponding to the end systolic aortic pressure determining means 90, the calculation is performed at SB7 from the time of occurrence of the second heart sound II. The magnitude of the estimated arterial pressure waveform BP (t), that is, the blood pressure value at a time after the set time difference TD is set to the end systolic aortic pressure P._esDetermine as. Next, at SB10, it is determined whether or not an estimated arterial pressure waveform BP (t) for one pulse wave, that is, one cycle has been generated. If the determination at SB10 is negative, this routine is terminated. If the determination is affirmative, at SB11 corresponding to the stroke amount estimation means 92, the actual relationship is determined from the preset relationship shown in the equation 4. Based on the estimated arterial pressure waveform BP (t), the stroke volume SV per beat of the left ventricle is calculated.
[0059]
Returning to FIG. 11, in SA8 corresponding to the left ventricular end systolic elastance calculation means 96, the cardiac mechanical efficiency E obtained in SA6 is obtained._a/ E_esAnd aorta effective elastance E obtained in SA7_aAnd left ventricular end systolic elastance E_esIs calculated and the value is displayed on the display 32, and a trend graph showing the change in the value is displayed on the display 32 as shown in FIG. The above SA6 and SA8 are the cardiac mechanical efficiency E_a/ E_esAnd left ventricular end systolic elastance E_esCorresponds to the display control means 98 that sequentially displays on the display 32 along a predetermined time axis.
[0060]
As described above, according to the present embodiment, as shown in FIG. 7, the pressure volume loop drawn for each beat is divided into two lines parallel to the volume axis and the systolic pressure line and the diastolic pressure line. The aorta effective elastance E is approximated to a rectangle composed of a systolic isovolume line and a diastole isovolume line which are two sides parallel to the pressure axis._aAnd left ventricular end systolic elastance E_esRatio, ie, heart machine efficiency E_a/ E_esCan be approximated by the ratio PEP / LVET between the cardiac precursor ejection time PEP and the ejection time LVET, the cardiac mechanical efficiency calculation means 88 (SA6) calculates the precursor ejection period from the preset relationship shown in Formula 1. Based on the precursor ejection period PEP determined for each beat by the determining means 84 (SA3) and the ejection period LVET determined for each beat by the ejection period determining means 86 (SA5), the heart machine efficiency E_a/ E_esTherefore, cardiac function can be easily monitored non-invasively.
[0061]
Further, according to this embodiment, the effective aortic elastance E calculated by the aorta effective elastance calculating means 94 (SA7) by the left ventricular end systolic elastance calculating means 96 (SA8)._aAnd the heart machine efficiency E calculated by the heart machine efficiency calculation means 88 (SA6)._a/ E_esBased on the left ventricular end systolic elastance E_esIs calculated so that left ventricular end systolic elastance E corresponding to cardiac function_esCan be easily measured non-invasively.
[0062]
According to the present embodiment, the heart sound microphone 62 is disposed in the vicinity of the heart in a body cavity such as the esophagus of the living body, and detects the first heart sound I and the second heart sound II generated from the heart of the living body. The precursor emission period determining means 84 (SA3) uses the time from the Q wave of the electrocardiographic induction waveform obtained from the electrocardiographic induction device 68 to the first end of the first heart sound I as the precursor emission period PEP. Therefore, there is an advantage that the precursor time PEP is accurately measured in a non-invasive manner.
[0063]
Further, according to the present embodiment, the ejection period determining means 86 (SA5) ejects the period from the end of the first heart sound I obtained from the heart sound detecting device 68 to the time when the second heart sound II is generated. LVET is calculated directly, or the precursor emission time PEP is subtracted from the interval (PEP + LVET) from the Q wave of the electrocardiographic induction waveform obtained from the electrocardiographic guidance device 68 to the second heart sound II. Therefore, the ejection period LVET is calculated from the time from the rising point of the estimated arterial pressure waveform BP (t) to the notch indicating the aortic valve closure. There is an advantage that it can be accurately calculated by invasion.
[0064]
Further, in this embodiment, the cardiac function monitoring device 8 has a ratio PEP / LVET between the precursor ejection period PEP and the ejection period LVET calculated sequentially by the cardiac machine efficiency calculating means 88 (SA6), that is, the cardiac machine efficiency E._a/ E_esAnd left ventricular end systolic elastance E calculated by the left ventricular end systolic elastance calculating means 96 (SA8)._esIs provided on the display 32 sequentially along a predetermined time axis, so that, for example, when the cardiac function of the patient is decreasing during the operation, the cardiac mechanical efficiency E_a/ E_esAnd left ventricular end systolic elastance E_esSince the change tendency of the cardiac function can be known more accurately than the trend, there is an advantage that the abnormal cardiac function can be predicted before reaching the abnormal value.
[0065]
In the present embodiment, the stroke volume estimating means 92 (SB11) calculates the stroke volume SV based on the estimated arterial pressure waveform BP (t) estimated by the arterial pressure waveform estimating means 80 (SB4). Therefore, there is an advantage that the stroke volume SV can be obtained without adding a detection device for detecting the stroke volume SV, such as an impedance measurement electrode, an impedance measurement circuit, and an ultrasonic image generator.
[0066]
As mentioned above, although one Example of this invention was described based on drawing, this invention is applied also in another aspect.
[0067]
For example, in the cardiac function monitoring device 8 of the above-described embodiment, the cardiac machine efficiency E_a/ E_esAnd left ventricular end systolic elastance E_esIs calculated and displayed, but the mechanical efficiency E_a/ E_esAnd left ventricular end systolic elastance E_esOnly one of them may be calculated or displayed.
[0068]
Further, in the end systolic aortic pressure determining means 90 described above, the end systolic aortic pressure P_esWas determined as the magnitude of the estimated arterial pressure waveform BP (t) at the time when the time difference TD has elapsed from the start time of the second heart sound II, but the end systolic aortic pressure P_esCan be approximated by the mean blood pressure value (mean arterial pressure) MAP based on an empirical rule, so that the mean value per one cycle T of the instantaneous blood pressure value obtained from the estimated arterial pressure waveform BP (t), that is, the mean blood pressure value MAP is the end systolic aortic pressure. P_esMay be determined as Since the average blood pressure value MAP is expressed as ΣBP (t) / T, it can also be expressed as a pressure value at the center of gravity of the estimated arterial pressure waveform BP (t) per cycle T.
[0069]
Further, the above-described stroke volume estimation means 92 calculates the stroke volume SV per beat based on the estimated arterial pressure waveform BP (t) from Equation 4, but this is known as the Kubicek method. It may be calculated based on an impedance cardiograph detected using electrodes attached to the cervical region and the lumbar region, or may be obtained using ultrasonic waves from the predetermined relationship. It may be calculated based on the width dimension of the heart image. When the cardiac output CO per minute is obtained, the cardiac output SV per beat can be obtained by dividing the cardiac output CO by the heart rate HR.
[0070]
The above description is merely an example of the present invention, and the present invention can be variously modified without departing from the spirit of the present invention.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a main part of a configuration of a cardiac function monitoring apparatus according to an embodiment of the present invention.
2 shows a correspondence relationship used for estimating an arterial pressure waveform from a pressure pulse wave detected by a pressure pulse wave sensor in the cardiac function monitoring apparatus of FIG. 1; FIG.
3 is a functional block diagram illustrating a main part of a control function of the arithmetic and control unit of the cardiac function monitoring apparatus of FIG. 1. FIG.
4 is a diagram showing an example of an arterial pressure waveform estimated by the arterial pressure waveform estimating means of FIG. 3. FIG.
5 explains the relationship between a precursor ejection period PEP and ejection period LVET determined by the precursor ejection period determining means and ejection period determining means in FIG. 3, and an aortic pressure waveform, an electrocardiographic induction waveform, and a heart sound. FIG. It is a time chart.
FIG. 6 is a diagram showing an example of the relationship between the volume and pressure in the left ventricle of a living body in a one-beat loop.
FIG. 7 is a diagram that approximates a rectangular shape of the pressure-volume loop as shown in FIG. 6, and the diagram and left ventricular end systolic elastance E_esAorta effective elastance E_aIt is a figure explaining the relationship with these.
FIG. 8: Various pressure volume loops and end systolic pressure-volume relationship line L_esIt is a figure explaining the relationship.
FIG. 9 is a diagram illustrating the relationship between left ventricular contraction time and left ventricular elastance.
10 shows a cardiac function monitoring apparatus of FIG._a/ E_esAnd left ventricular end systolic elastance E_esIt is a figure which shows the example of the trend graph displayed on a display.
FIG. 11 is a flowchart for explaining a main part of the control operation of the arithmetic and control unit of the cardiac function monitoring apparatus of FIG. 1 and showing a main routine.
12 is a flowchart for explaining a main part of the control operation of the arithmetic and control unit of the cardiac function monitoring apparatus of FIG. 1, showing an estimated arterial pressure waveform, end systolic aortic pressure, and a stroke volume calculating routine.
[Explanation of symbols]
62: Heart sound microphone (heart sound detection device)
68: ECG induction device
80: Arterial pressure waveform estimation means
84: Precursor ejection period determining means
86: Ejection period determination means
88: Heart machine efficiency calculation means
90: End systolic aortic pressure determining means
92: Stroke volume estimation means
94: Aorta effective elastance calculation means
96: Left ventricular end systolic elastance calculation means

Claims (1)

A cardiac function monitoring device for monitoring the function of a living heart based on cardiac mechanical efficiency,
From shrinkage starting of the left ventricle of the living body, and pre-ejection period determining means blood from the left ventricle is pre determined non-invasively the time out until the ejection,
Ejection to determine the interval from the end of the first heart sound included in heart of the living body until the occurrence of the second heart sound, non-invasively as ejection periods are ejected blood from the left ventricle of the living body A period determination means;
A cardiac machine efficiency calculating means for calculating a cardiac machine efficiency of the living body based on the precursor ejection period and the ejection period from a preset relationship;
Aortic pressure estimating means for estimating the aortic pressure of the living body;
Based on the aortic pressure estimated by the aortic pressure estimating means, the end-systolic aortic pressure determining means for determining the aortic internal pressure at the end systolic stage of the living body,
Stroke volume estimation means for non-invasively estimating the stroke volume per beat of the left ventricle of the living body,
Based on the aortic internal pressure at the end systole of the left ventricle determined by the end systolic aortic pressure determining means from a preset relationship and the output per beat of the left ventricle estimated by the stroke amount estimating means Aorta effective elastance calculating means for calculating aortic effective elastance,
Left ventricular end systolic elastance calculating means for calculating a left ventricular end systolic elastance based on the aortic effective elastance calculated by the aortic effective elastance calculating means and the cardiac mechanical efficiency calculated by the cardiac mechanical efficiency calculating means And a cardiac function monitoring device.

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