Objective To investigate the application value of inferior vena cava variability（ΔIVC） combined with lung recruitment maneuver（LRM） in volume responsiveness assessment in patients with acute circulation failure.Methods Fifty-three patients with acute circulation failure undergoing mechanical ventilation admitted to intensive care unit of my hospital from January 2018 to December 2020 were enrolled.Lung recruitment maneuver and volume expansion（VE） were performed in sequence.The hemodynamic parameters including mean arterial pressure（MAP），central venous pressure（CVP），stroke volume variation（SVV），global end-diastolic volume index（GEDI），cardiac index（CI） and the variation ratio in cardiac index after lung recruitment maneuver(ΔCILRM) were monitored by pulse indicator continuous cardiac output before and during lung recruitment maneuver.The patients were divided into reaction group（ΔCIVE≥15％）28 cases and non-reaction group（ΔCIVE＜15％）25 cases according to the variation ratio in cardiac index after volume expansion（ΔCIVE）.Inferior vena cava diameter and ΔIVC were measured by ultrasonography during lung recruitment maneuver.The difference of the above hemodynamic parameters between the two groups were compared

and the correlations between the above hemodynamic parameters and ΔIVC were analyzed.Receiver operation characteristic (ROC) curve was drawn to predict the accuracy of all hemodynamic parameters for volume responsiveness.Results SVV before lung recruitment maneuver and during lung recruitment maneuver in reaction group was significantly higher than the of the non-reaction group（P＜0.05）.Both in reaction group and non-reaction group，SVV was significantly increased during lung recruitment maneuver as compared with that at before lung recruitment maneuver（P＜0.05）. ΔDIVC和ΔIVC in reaction group were significantly higher than those of the non-reaction group during lung recruitment maneuver（all P＜0.05）.MAP，SVV，ΔCILRM and ΔCIVE were linearity correlated with ΔIVC during lung recruitment maneuver.（r value was -0.279、0.409、0.807、0.800 respectively，all P ＜0.05），ΔCILRM was linearity correlated with ΔCIVE（r=0.894，P＜0.05），while no correlation was found between CVP and ΔIVC as well as GEDI and ΔIVC（r value was -0.106、0.107 respectively，all P >0.05）.The area under ROC curve of SVV，ΔIVC and ΔDIVC during lung recruitment maneuver for predicting fluid responsiveness was 0.891、0.770、0.747，respectively.When the cut-off value of SVV was 14.5%，the sensitivity was 60.7%，and the specificity was 100.0%.When the cut-off value of ΔIVC was 12.9%，the sensitivity was 78.6%，and the specificity was 72.0%.When the cut-off value of ΔDIVC was 0.25cm，the sensitivity was 46.4%，and the specificity was 88.0%.Conclusion Echocardiography assessment of ΔIVC combined with lung recruitment maneuver could accurately predict volume responsiveness in acute circulation failure patients with mechanical ventilation.