広島大学生体システム論研究室では約10年前に人工心肺に関する研究を開始し，博士課程修了生の岡原 重幸先生（純真学園大学保健医療学部 准教授），博士課程後期在学中の高橋 秀暢先生（広島国際大学保健医療学部 講師），宮本 聡史さん（広島大学病院診療支援部臨床工学部門 部門長）とともに，血液粘度推定，人工心肺装置の自動制御，血中マイクロバブル発生数の推定などの研究課題に取り組んできました．
—–これまでの研究成果————————————————
■国際学術雑誌（インパクトファクタは論文掲載時の値）
Hydrodynamic characteristics of a membrane oxygenator: modeling of pressure-flow characteristics and their influence on apparent viscosity
Shigeyuki Okahara, Toshio Tsuji, Shinji Ninomiya, Satoshi Miyamoto, Hidenobu Takahashi, Zu Soh and Taijirou Sueda
Perfusion, Vol. 30, pp.478-483, first published on December 2, 2014, doi:10.1177/0267659114562101, September 2015 (SCI, IF=1.442).
A novel blood viscosity estimation method based on pressure-flow characteristics of an oxygenator during cardiopulmonary bypass
Shigeyuki Okahara, Zu Soh, Satoshi Miyamoto, Hidenobu Takahashi, Hideshi Itoh, Shinya Takahashi, Taijiro Sueda and Toshio Tsuji
Artificial Organs, Vol.41, No.3, pp.262-275 (Thoughts & Progress), 2017 (SCI, IF=1.993).
Continuous Blood Viscosity Monitoring System for Cardiopulmonary Bypass Applications
Shigeyuki Okahara, Zu Soh, Satoshi Miyamoto, Hidenobu Takahashi, Shinya Takahashi, Taijiro Sueda and Toshio Tsuji
IEEE Transactions on Biomedical Engineering, Vol.64, No.7, pp. 1503-1512, DOI:10.1109/TBME.2016.2610968 , JULY 2017 (SCI, IF=3.577)
Online Prediction of Normal Blood Viscosity During Cardiopulmonary Bypass Using Hematocrit- and Temperature-Dependent Model
Shigeyuki Okahara, Satoshi Miyamoto, Zu Soh, Hideshi Itoh, Shinya Takahashi, and Toshio Tsuji
IEEE Access, Volume: 8, Issue:1, pp. 5611-5621, Digital Object Identifier: 10.1109/ACCESS.2019.2963355, Date of publication December 31, 2019 (SCI, IF=4.098)
Steady-state Model of Pressure-flow Characteristics Modulated by Occluders in Cardiopulmonary Bypass Systems
Hidenobu Takahashi, Zu Soh, and Toshio Tsuji
IEEE Access, Volume: 8, pp. 220962-220972, Digital Object Identifier: 10.1109/ACCESS.2020.3043470, Date of Publication: 09 December 2020 (SCI, IF=3.745)
Neural network-based modeling of the number of microbubbles generated with four circulation factors in cardiopulmonary bypass
Satoshi Miyamoto, Zu Soh, Shigeyuki Okahara, Akira Furui, Taiichi Takasaki, Keijiro Katayama, Shinya Takahashi, and Toshio Tsuji
Scientific Reports, volume 11, Article number: 549, doi.org/10.1038/s41598-020-80810-3, Published online: 12 January 2021. (SCI, IF=3.998)
■国際会議
A blood viscosity estimation method based on pressure-flow characteristics of an oxygenator during cardiopulmonary bypass and its clinical application
Shigeyuki Okahara, Toshio Tsuji, Zu Soh, and Taijiro Sueda
Proceedings of 37th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC’15), pp. 5525-5528, Milano, Italy, August 25th-29th, 2015.
Blood Viscosity Monitoring During Cardiopulmonary Bypass Based on Pressure-Flow Characteristics of a Newtonian fluid
Shigeyuki Okahara, Zu Soh, Shinya Takahashi, Taijiro Sueda and Toshio Tsuji
The 38th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC f16), pp. 2331-2334, Orlando, Florida, U.S.A., August 16th-20th, 2016.
Detection of Echinocyte during Perfusion with Oxygenator Based on Continuous Blood Viscosity Monitoring
Shigeyuki Okahara, Toshio Tsuji, Zu Soh, and Satoshi Miyamoto
Proceedings of 40th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC’18), pp. 4448-4451, Honolulu, HI, USA, July 17-21, 2018.
Automatic control of blood flow rate on the arterial-line side during cardiopulmonary bypass
Hidenobu Takahashi, Takuya Kinoshita, Zu Soh, and Toshio Tsuji
Proceedings of 43rd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC’21), pp. 5011-5014, Virtual Conference due to COVID-19, Nov 1-5, 2021.
Neural Network-based Estimation of Microbubbles Generated in Cardiopulmonary Bypass Circuit: A Clinical Application Study
Satoshi Miyamoto, Zu Soh, Shigeyuki Okahara, Akira Furui, Keijiro Katayama, Taiichi Takasaki, Shinya Takahashi, and Toshio Tsuji
Proceedings of 44th Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC’22), DOI: 10.1109/EMBC48229.2022.9871662, Glasgow, United Kingdom, 11-15 July 2022.
■特許
血液循環システムの制御装置、制御方法及びプログラム
日本国特許出願 特願2022-207247
辻 敏夫, 曽 智, 木下 拓矢, 高橋 秀暢
2022年12月23日出願
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今回新たに，曽 智先生，木下 拓矢先生（広島大学大学院先進理工系科学研究科 システム制御論研究室 助教）とともに人工心肺装置における静脈リザーバーレベルと送血側血流量の同時制御に成功し，IEEE Journal of Translational Engineering in Health & Medicineに論文がアクセプトされました．
Simultaneous Control of Venous Reservoir Level and Arterial Flow Rate in Cardiopulmonary Bypass with a Centrifugal Pump
Hidenobu Takahashi, Takuya Kinoshita, Zu Soh, Shigeyuki Okahara, Satoshi Miyamoto, Shinji Ninomiya, and Toshio Tsuji
IEEE Journal of Translational Engineering in Health & Medicine, Volume: 11, pp.435-440, doi:10.1109/JTEHM.2023.3290951, 30 June 2023. (SCI, IF=3.4)
URL: https://ieeexplore.ieee.org/document/10168928
PDF: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10168928
この論文は高橋先生の博士学位論文の一部になる予定です．今後も本研究チームとともに研究を継続し，臨床での研究成果につなげていければと思っています．ひきつづきよろしくお願いします．
<論文内容>
Cardiopulmonary bypass (CPB) is an indispensable technique in cardiac surgery, providing the ability to temporarily replace cardiopulmonary function and create a bloodless surgical field. Traditionally, the operation of CPB systems has depended on the expertise and experience of skilled perfusionists. In particular, simultaneously controlling the arterial and venous occluders is difficult because the blood flow rate and reservoir level both change, and failure may put the patient’s life at risk. This study proposes an automatic control system with a two-degree-of-freedom model matching controller nested in an I-PD feedback controller to simultaneously regulate the blood flow rate and reservoir level. CPB operations were performed using glycerin and bovine blood as perfusate to simulate flow-up and flow-down phases. The results confirmed that the arterial blood flow rate followed the manually adjusted target venous blood flow rate, with an error of less than 5.32%, and the reservoir level was maintained, with an error of less than 3.44% from the target reservoir level. Then, we assessed the robustness of the control system against disturbances caused by venting/suction of blood. The resulting flow rate error was 5.95%, and the reservoir level error 2.02%. The accuracy of the proposed system is clinically satisfactory and within the allowable error range of 10% or less, meeting the standards set for perfusionists. Moreover, because of the system’s simple configuration, consisting of a camera and notebook PC, the system can easily be integrated with general CPB equipment. This practical design enables seamless adoption in clinical settings. With these advancements, the proposed system represents a significant step towards the automation of CPB.
心肺バイパスは心臓手術において不可欠な手技であり，一時的に心肺機能を代替し，無血の術野を形成する能力を提供する．従来，人工心肺装置の操作は熟練した灌流技師の専門知識と経験に依存していた．特に，動脈と静脈のオクルーダを同時に制御することは，血流量とリザーバーレベルの両方が変化するため困難であり，失敗すれば患者の生命を危険にさらすことになりかねない．本研究では，I-PDフィードバックコントローラに2自由度モデルマッチングコントローラをネストした新たな自動制御システムを提案し，血流量とリザーバレベルを同時に調節する．灌流液としてグリセリンと牛血液を用いて人工心肺操作を行い，フローアップ期とフローダウン期をシミュレートした．その結果，送血血流量は手動で調整した目標脱血血流量に追従し誤差は5.32%以下であり，リザーバーレベルは目標リザーバーレベルから3.44%以下の誤差で維持されることが確認された．次に，血液の排出/吸引によって引き起こされる外乱に対する制御システムのロバスト性を評価した．その結果，流量誤差は5.95％，リザーバレベル誤差は2.02％であった．提案されたシステムの精度は臨床的な許容誤差範囲である10％以内であり，灌流技師の基準を満たすものである．さらに，本システムはカメラとノートPCからなるシンプルな構成であるため，一般的な人工心肺装置と容易に統合することができる．この実用的な設計により，臨床現場でのシームレスな導入が可能となった．これらの進歩により，提案されたシステムは人工心肺操作の自動化に向けた重要な一歩となる．
