전달함수를 이용한 대동맥 펄스 추정 및 동맥경화도 진단을 위한 증강점 검출 알고리즘 개선에 관한 연구 = Estimation of the central aortic pulse using transfer function and improvement of an augmentation point detection algorithm for diagnosing arterial stiffness

다국어 초록 (Multilingual Abstract)

Aortic AIx(augmentation index) has been used to measure aortic stiffness quantitatively and even to evaluate ventricular load. Due to its advantage, aortic AIx has a special attention for the measurement of arterial stiffness. However, in order to calculate aortic AIx, catheters should be inserted to the subjects’ artery, which hampers its clinical usage. To overcome such limitation, aortic AIx has been indirectly calculated by estimating aortic pressure wave from the peripheral arterial pulse by applying transfer functions. An augmentation point as the most important factor for the calculation of an AIx can be detected through fourth derivatives of pulse waves and find zero-crossing points on the negative gradient. This measurement, however, possesses disadvantages because of its significant error rate, which depends on the age and disease. In this study, central aortic pressure waves using Millar catheter and radial artery pulse waves using tonometry pressure sensor were measured to establish transfer functions for an estimation of central aortic pressure waves from radial artery pulse waves. Also, an algorithm which detects dicrotic notch and augmentation point for the calculation of AIx were developed. Developed algorithm for the detection of dicrotic notch and augmentation point gradually increases the differential order to detect inflection point rather than detects the distinctive point that appears after a specific time. Transfer functions were established using 10th order ARX model and were verified for the stability of the transfer function through residual analysis. In addition, correspondence between two pulse waves were studied by setting systolic pressure, pulse pressure, ejection time, AIx, and RWTT (reflected wave transit time) using measured aortic pressure waves and the estimated aortic pressure waves. Evaluation of an algorithm for the detection of dicrotic notch and augmentation point were performed by comparing the augmentation points obtained from developed algorithm with the known augmentation points synthesized in various conditions. On the comparison between measured aortic pressure waves and estimated aortic pressure waves for each variable, similar results were observed for all the variables except AIx. For the detection of an AIx, percent errors were significantly decreased from -39±39.4% to 5.31±17.0%, and -54±232% from 13.04±27.26% for individual transfer function and for generalized transfer function, respectively. In addition, developed algorithm for the AIx is proved to provide more accurate results than the ones developed by previous studies for the deviation from -11.5±14.34 points to -3.75±1.26 points. The significance of the study was in two folds. Firstly, the results could provide the basis for the measurement of aortic stiffness using easily-measurable radial artery pulse waves, and secondly, extension of the study may enable the early diagnosis of various vascular diseases.

목차 (Table of Contents)

• 제 1 장 서론 1
• 제 2 장 연구배경 = 4
• 2.1 동맥 경직도 = 4
• 2.1.1 혈관의 구조와 기능 = 4
• 2.1.2 동맥의 종류 = 6
• 2.1.3 혈압과 동맥의 탄성 = 8
• 2.1.4 맥파 = 12
• 2.2 맥파의 변수 검출 = 18
• 2.3 전달함수 = 23
• 2.3.1 시스템 식별 = 23
• 2.3.2 Nonparametric model estimation = 23
• 2.3.3 Parametric model estimation = 27
• 2.3.4 대동맥 압력파 추정 전달함수 = 32
• 제 3 장 연구 목적 = 35
• 제 4 장 연구 방법 = 37
• 4.1 실험 설계 = 37
• 4.2 측정 시스템 및 데이터 수집 = 40
• 4.2.1 측정 시스템 = 40
• 4.2.2 데이터 수집 = 47
• 4.3 전달함수 수립 = 51
• 4.3.1 데이터 전처리 = 51
• 4.3.2 ARX 모델 구현 및 검증 = 54
• 4.4 증강점 검출 알고리즘 = 58
• 4.5 데이터 분석 = 74
• 제 5 장 연구 결과 = 77
• 5.1 증강점 검출 = 77
• 5.2 전달함수 구현 = 88
• 제 6 장 토의 및 고찰 = 103
• 제 7 장 결론 = 109
• 참고문헌 = 112