Method, apparatus and system for determining the moment when the state of an artery switches from open to closed and vice versa for an artery of interest under pressure fluctuations
The method of determining the open/closed switch moment of an artery of interest under a changing pressure comprises: detecting a first Doppler ultrasound signal from the blood flow in the artery of interest using a first Doppler ultrasound transducer, which is placed on the artery of interest in one limb which is provided with a cuff that is capable of being inflated or deflated to provide the changing pressure to the artery of interest； detecting a second Doppler ultrasound signal from the blood flow in a reference artery using a second Doppler ultrasound transducer, the reference artery being in any one of the other three limbs； deriving a third signal from the first Doppler ultrasound signal and the second Doppler ultrasound signal, the third signal indicating the degree of synchronism between the first Doppler ultrasound signal and the second Doppler ultrasound signal； and out-putting a fourth signal to indicate the artery of interest is closed or reopened at the moment when the third signal satisfies a predefined condition. By utilizing the second ultrasound signal as a reference and deriving a signal indicating the synchronization property between the two ultrasound signals, the open/closed status of the artery of interest under a changing pressure can be determined more stably and more reliably regardless of the detailed condition of the patient.圧力変動下で関心動脈の開／閉スイッチの瞬間を決定する方法は以下のステップを有する：関心動脈へ変化する圧力を与えるように膨張若しくは収縮されることができるカフをつけた一肢の関心動脈上に置かれる、第１のドップラ超音波振動子を用いて関心動脈内の血流から第１のドップラ超音波信号を検出するステップ；第２のドップラ超音波振動子を用いて基準動脈内の血流から第２のドップラ超音波信号を検出するステップ、基準動脈は他の三肢のいずれか一つにある；第１のドップラ超音波信号と第２のドップラ超音波信号から第３の信号を得るステップ、第３の信号は第１のドップラ超音波信号と第２のドップラ超音波信号の間の同期の程度を示す；第３の信号が所定条件を満たす瞬間において関心動脈が閉じる若しくは再び開くことを示す第４の信号を出力するステップ。第２の超音波信号を基準として利用し、二つの超音波信号間の同期特性を示す信号を得ることによって、圧力変動下での関心動脈の開／閉状態が患者の詳細な状態にかかわらずより安定してより確実に決定され得る。
