Research On Hemodynamics Compensatory Model And Non-Invasive Monitoring Approaches Of Shock

Shock is an acute disease with high mortality.It is reported that real time monitoring of the blood pressure(BP),the effective blood volume(EBV),and the blood loss volume(BLV)could alert shock early and significantly decrease the mobility and mortality of shock patients.The photoplethysmography(PPG)is a noninvasive monitoring approach contains numerous hemodynamic information,which has great potential in shock monitoring.The key factors of achieving PPG based shock monitoring are analyzing the dynamics of body’s hemodynamics parameters and their hemodynamics association.However,current PPG based monitoring techniques are developed on heathy people,which can’t precisely describe the dynamics variation in body’s hemodynamics parameters under control of shock compensatory responses(CR),the hemodynamic association for PPG and three shock monitoring indexes became unclear.So a comprehensive study on CR is required.In this study,we aim to develop PPG based shock monitoring methods by conducting a comprehensive study on CR.We first built a hemodynamics analytical model of shock,and explored the method of analyzing the dynamics of body’s hemodynamics parameter under CR.Based on this analyzing method,we analyzed the dynamics of shock hemodynamics index and mined hemodynamic association for PPG and three shock indexes.We then developed algorithms for monitoring BP,EBV and BLV using PPG,and performed those algorithms on human and animal experimental data.Researches conducted in this thesis solve the problem that,hemodynamics under CR is unclear and achieve PPG based shock monitoring.The study we presented in this thesis has the following contents:First,modeling of shock hemodynamic CR.It is difficult to accurately measure and describe the body hemodynamics under the CR.Based on the human blood circulation system,a shock hemodynamic analytical model with autonomic nervecontrolled CR was established.By simulating the shock process,key parameter the compensatory factor(CF)that can be estimated by heart rate variability parameters is proposed to describe the CR,and an analytical method is proposed to analyze the hemodynamic parameters under the CR.Research conducted in this section provide a theoretical analysis tool for later mining the hemodynamic association between PPG and shock indexes under the CR and realizing non-invasive shock monitoring.Second,continuous BP monitoring algorithm based on vascular resistance compensation.Due to the vascular resistance compensation in shock,it is difficult to realize non-invasive continuous BP monitoring for shock patients.Based on the dynamic hemodynamic of PPG in arteries,the resistance compensation during shock is described by integrating PPG intensity and CF,and a BP monitoring algorithm based on PPG under vascular resistance compensation is proposed.The proposed blood pressure algorithm was tested in 31 normal subjects,29 patients with hypertension and 31 patients with shock.The proposed algorithm makes up for the disadvantage that the existing blood pressure algorithms do not consider resistance compensation,and realizes high-precision non-invasive continuous BP monitoring for shock patients.Third,hypovolemia monitoring based on vascular volume compensation.It is difficult to monitor the state of hypovolemia due to the redistribution of blood volume caused by vascular volume compensation in shock.Based on the hemodynamic of PPG in arteriovenous circulation,the relative change of circulating blood volume during shock is described by integrating PPG hemodynamic characteristic matrix and volume compensation dynamic,and a hypovolemia monitoring algorithm under vascular volume compensation is proposed.Besides,animal experient with a 59 pigs sample size were designed and carried out to verify the proposed algorithm.The performance of the proposed non-invasive hypovolemia monitoring algorithm is much better than the existing algorithms based on invasive signals,and can be widely used in out of hospital,like emergency medical services.Fourth,estimating the BLV by eliminating the blood volume compensation.during the shock interval,the CR of blood volume may cause the ‘resuscitation’ of physiological signal,resulting in the inaccurate estimation of BLV.The ‘resuscitation’phenomenon of PPG during shock interval is analyzed to discriminate the shock interval.Based on the hemodynamics of PPG in arteriovenous blood loss,a BLV estimation algorithm is proposed,and the concept of compensated blood volume is proposed to eliminate the error of BLV estimation caused by the ‘resuscitation’.The proposed BLV estimation algorithm was tested on animal data,and achieves continuous and high-precision blood loss monitoring in each stage of blood loss.Its performance is far more than twice that of the existing clinical BLV estimation methods.