Development of Noninvasive Artificial Baroreflex System for Severe Orthostatic Hypotension

中老年人进行性神经退行性疾病引起的压力反射衰竭可导致严重的直立性低血压和晕厥。然而，常用的干预措施不能恢复功能，大多数患者仍然卧床不起。为此，我们研制了无创性人工压力感受器反射系统，并进行了两年的临床研究.压力反射开环函数的估计：通过比较自主神经功能衰竭患者与正常人估计的Hnative（f）的开环传递函数显示低通特性，截止频率为0.01Hz。最低频率下的稳态增益为5.3.2。HSTM-SAP（f）从腹部裤压到动脉压（AP）的传递函数的估计：自主神经衰竭患者的平均阶跃反应函数显示，通过突然增加裤压，AP反应快速达到稳态的90%。最低频率下的稳态增益为0.7±0.3 mmHg/mmHg。3.人工血管中心的设计：用平均HSTM-SAP（f）数值模拟了对裤子压力的瞬时AP反应。基于这些结果，将Kp的比例校正因子设定为0.4，将Ki的积分校正因子设定为0.2，使得该系统可以快速有效地减弱AP下降的影响。利用这些校正因子，将系统引入人工血管中心.系统的建立及临床应用：该装置由带血管中心的PC机、AP监护仪、电磁控制阀、压缩空气瓶和腹式空气裤组成。突然倾斜导致AP快速进行性下降约20 mmHg，当系统激活时，AP下降减弱AP下降11 mmHg。用大腿和小腿袖带进行AP控制的可能性阶跃响应功能显示，通过在20秒内突然增加袖带压力，AP对稳态的快速响应。

Baroreflex failure due to progressive neurodegenerative diseases in middle age and elderly induced severe orthostatic hypotension and syncope. However, commonly used intervention can not restore the function and most affected patients remain bedridden. Therefore, we developed noninvasive artificial baroreflex system with clinical investigation for two years.1. Estimation of baroreflex open-loop function : The open-loop transfer function of Hnative(f) estimated by comparing autonomic failure patients to normal subjects showed low-pass characteristics with a cut off frequency of 0.01Hz. The steady-state gain at the lowest frequency was 5.3.2. Estimation of transfer function of HSTM-SAP(f) from abdominal pants pressure to arterial pressure (AP) : Averaged step response function in patients with autonomic failure showed rapid AP response to 90% of steady state by abrupt increase of pants pressure. The steady-state gain at the lowest frequency was 0.7±0.3 mmHg/mmHg.3. Design of artificial vasomotor center : The instantaneous AP response to pants pressure was numerically simulated with the averaged HSTM-SAP(f). Based on these results, proportional correction factor of Kp was set at 0.4, and integral correction factor of Ki was set at 0.2, so that the system could quickly and effectively attenuate the effect of the AP decline. The system was leaded the artificial vasomotor center with these correction factors.4. Setting up of the system and clinical application : The devise was composed of PC with the vasomotor center, AP monitor, solenoid control valve, compressed air cylinder and abdominal air pants. A sudden tilting produced a rapid progressive fall in AP of approximately 20 mmHg, when the system was activated, the AP fall was attenuate the drop in AP of 11mmHg.5. Possibility of AP control with a thigh and lower leg cuff A step response function showed rapid AP response to the steady state by abrupt increase of cuff pressure in 20 seconds.