Development of Noninvasive Artificial Baroreflex System for Severe Orthostatic Hypotension

中老年进行性神经退行性疾病导致的压力感受性反射衰竭导致严重的直立性低血压和晕厥。然而，常用的干预措施无法恢复功能，大多数受影响的患者仍然卧床不起。为此，我们经过两年的临床研究，研制了无创人工压力感受器系统。压力感受性反射开环功能的估计：自主神经功能衰竭患者与正常受试者比较，Hative(F)的开环传递函数呈现低通特征，截止频率为0.01赫兹。最低频率的稳态增益为5.3.2。HSTM-SAP(F)从腹裤压到动脉压传递函数的估计：自主神经衰竭患者的平均阶跃反应函数显示，通过裤子压力的突然增加，AP对90%的稳态状态有快速反应。最低频率下的稳态增益为0.7±0.3毫米汞柱/毫米汞。人工血管运动中枢的设计：用HSTM-SAP(F)平均模型数值模拟AP对裤子压力的瞬时反应。在此基础上，将Kp的比例校正因子设置为0.4，将Ki的积分校正因子设置为0.2，从而使系统能够快速有效地衰减AP下降的影响。通过这些校正因子，系统引入了人工血管收缩中枢。该系统的建立及临床应用：该装置由带有血管运动中心的PC机、AP监护仪、电磁控制阀、压缩气瓶和腹部气裤组成。突然倾斜导致AP快速递增下降约20毫米汞柱，当系统被激活时，AP下降减弱了AP下降11 mm Hg.5。使用大腿和小腿袖带控制AP的可能性A阶跃反应函数显示AP在20秒内突然增加袖带压力对稳态AP有快速反应。

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.