The Research Of Physiological Monitoring Of G-LOG And Protective Effect Of Liquid-Filled Anti-G Device

As the maneuverability of fighter jets continues to improve,the+Gz values generated by flight have far exceeded the physiological tolerance limit of pilots.Under the action of high+Gz,the thoracic and abdominal organs of pilots are displaced and deformed,the differential hydrostatic pressure of the blood column increases,the blood is redistributed and shifted to the lower body,head（eye）-level arterial blood pressure decreases,and the brain becomes acutely ischemic and hypoxic,resulting in G-induced loss of consciousness（G-LOC）.G-LOC seriously affects operational ergonomics,threatens flight safety,and even leads to catastrophic consequences of aircraft destruction and human death.However,the physiological mechanisms of G-LOC have not been completely elucidated,and the protective effects of existing anti-G measures are relatively limited.Therefore,the research on physiological monitoring during high+Gz exposure and the development of new anti-G devices are of far-reaching significance for the exploration of the mechanism of G-LOC,the study of warning technology and the improvement of the performance of anti-G devices.In this study,we propose to monitor the changes of physiological parameters such as eye-level arterial blood pressure,ECG and respiration on miniature swine through centrifuge animal experiments,combined with ABG analysis and cardiopulmonary histopathological examination,in an attempt to explore the physiological mechanisms of G-LOC and to screen out the physiological indicators that can be used for warning of G-LOC.In addition,we intend to use the extended-coverage liquid-filled anti-G device for physiological protection research,verify its protective effect,and provide basic experimental data for the next research of human extended-coverage liquid-filled anti-G suit.PartⅠThe physiological monitoring of G-LOCObjective:Explore the physiological mechanisms of G-LOC,and screen out the physiological indicators that can be used for warning of G-LOC.Methods:A human centrifuge was used to simulate+Gz exposure（baseline+1.4 Gz,onset rate1 G/s,peak+8 Gz,duration 60 s）.An aerospace-specific multi-parameter physiological signal acquisition system was used to monitor eye-level arterial blood pressure and+Gz values on miniature swine（n=10）.We used a drop in eye-level arterial blood pressure to 0mm Hg as a criterion for loss of consciousness（+Gz tolerance end-point）.The physiological parameters detecting device was used to monitor physiological signals such as ECG and respiration.Compare changes of ABG and cardiopulmonary histopathology before and after+Gz exposure.Results:1.Eye-level arterial blood pressure of miniature swine decreased to 0 mm Hg at+（4.85±1.38）G;2.ECG vector direction changes（ECG QRS wave direction changes from positive to negative with a QS pattern）at+（4.76±1.42）G.Compared with the value of+Gz tolerance end-point,there was no significant difference（P>0.05）;3.No significant changes in HR and ST-T and no arrhythmias on miniature swine at+Gz tolerance end-point;4.During the rise of+Gz,the respiratory wave of miniature swine was characterized by"Cheyne-Stokes respiration"with slower frequency and reduced amplitude,and the respiratory pause time was about（14.43±3.72）s;5.There was a significant increase in PCO₂,Lac,Shunt,Aa Dp O₂ and a significant decrease in PO₂,SO₂,ABE on miniature swine after+Gz exposure,which suggests a combination of respiratory acidosis with metabolic acidosis.6.After+Gz exposure,focal ischemia with myofibrillar interstitial congestion occurred in both the left and right subendocardial myocardium of miniature swine.There was generalized atrophy of the lung tissue with focal hemorrhage and localized alveolar dilatation on the thoracic side of the right upper lobe.Conclusion:Our study further confirms the theory of ischemia/hypoxia for G-LOC,and suggests the possibility of ECG vectors for warning of G-LOC for the first time.PartⅡThe protective effect of extended-coverage liquid-filled anti-G deviceObjective:Verify the protective effect of extended-coverage liquid-filled anti-G device,and provide basic experimental data for the next research of human extended-coverage liquid-filled anti-G suit.Methods:Miniature swine were randomly divided into two groups:the group without any anti-G measures（control group,n=10）and the group with the extended-coverage liquid-filled anti-G device（protection group,n=9）.Both groups were exposed to high+Gz（baseline+1.4 Gz,onset rate 1 G/s,peak+8 Gz,duration 60 s）.Monitoring eye-level arterial blood pressure and+Gz values of miniature swine with an aerospace-specific multi-parameter physiological signal acquisition system.A drop in eye-level arterial blood pressure to 0 mm Hg was used as the criterion for loss of consciousness（+Gz tolerance end-point）.Compare the changes of+Gz tolerance and eye-level arterial blood pressure between the two groups.Results:1.There was a significant difference in+Gz tolerance of miniature swine between two groups.The protection group was higher than that in the control group（P<0.01）;2.The decrease of eye-level arterial blood in protection group was significantly lower than that in the control group during+Gz exposure（P<0.01）;3.In control group,the mean eye-level arterial pulse-pressure difference during+Gz exposure was significantly lower than that before+Gz exposure（P<0.01）,while the mean pulse-pressure difference during+Gz exposure in the protection group was not significantly different from that before exposure（P>0.05）.Conclusion:The use of extended-coverage liquid-filled anti-G device can significantly improve+Gz tolerance of miniature swine,mitigate the reduction of eye-level arterial blood pressure,and maintain eye-level arterial pulse-pressure difference.