An Observational Study On The Effects Of Different Mechanical Ventilation Levels On Right Heart Function In Patients

Objectives:The aim of this study is to investigate the effects of different levels of mechanical ventilation on right ventricular function and prognosis in patients receiving Invasive mechanical ventilation（IMV）in Intensive care unit（ICU）.To provide a basis for right heart protective ventilation strategy and evaluate the prognosis of patients.Methods:A total of 372 adult patients who were admitted to the ICU of Taizhou People’s Hospital and received invasive mechanical ventilation for 24 hours from January,2022 to December,2022 were included in the study.154 patients were excluded because they did not meet the inclusion criteria,and 163 patients were finally recruited for data collection.The relevant medical history and clinical data of the recruited patients were collected through the hospital’s electronic medical record system,including:general information,arterial blood gas analysis results,and relevant clinical scoring.Ventilator parameters were recorded,including ventilator mode,ventilator settings,tidal volume,positive end-expiratory pressure,plateau pressure,driving pressure were included,and right heart function indexes,mainly including:The ratio of right ventricular end-diastolic area to left ventricular end-diastolic area（RV/LV）,Right ventricular-fractional area change（RV-FAC）,Tricuspid annular plane systolic excursion（TAPSE）,Tissue Doppler–derived tricuspid lateral annular systolic velocity（S’）,The right ventricle diastolic early stage peak（E）,The right ventricle diastolic late stage peak（A）,and myocardium of the early diastolic velocity（e’）.Echocardiographic data were collected before the initiation of mechanical ventilation and after 24 hours of mechanical ventilation.Ventilator parameters were collected at 8:00 and 17:00 daily.Study groups:1)Patients were divided into low tidal volume group（VT:4-6ml/Kg）and medium tidal volume（VT:8-10 ml/Kg）to observe the effect of VT on right ventricular function and prognosis;After 24 hours of mechanical ventilation,according to whether they had right ventricular dysfunction（RVD）,the patients were grouped to investigate the effects of different levels of mechanical ventilation on right ventricular function.Patients were divided into ARDS subgroup and non-ARDS subgroup according to the presence or absence of ARDS.The ARDS subgroup was also divided into low tidal volume group（VT 4-6ml/Kg standard weight）and moderate tidal volume（VT 8-10ml/Kg standard weight）.After 24 hours of mechanical ventilation,the patients were divided into RVD group and non-RVD group according to the presence or absence of right ventricular dysfunction.The non-ARDS subgroup was also divided into low tidal volume group（VT:4-6ml/Kg standard body weight）and moderate tidal volume（VT:8-10 ml/Kg standard body weight）.According to the presence or absence of right ventricular dysfunction,the patients were divided into RVD group and non-RVD group.The effects of different tidal volumes on right ventricular function and prognosis were investigated,the prognosis was 28-day mortality;the effects of different levels of mechanical ventilation（tidal volume,plateau pressure,positive end-expiratory pressure,driving pressure）on right ventricular function were investigated as well.Results:1.Effect of mechanical ventilation on right ventricular function and prognosis of patients（1）Clinical characteristics:64 of 163 patients were treated with low tidal volume ventilation strategy,and the mean tidal volume was 5.37±0.82ml/Kg.99 subjects underwent moderate tidal volume ventilation strategy,and the mean tidal volume was8.94±0.84ml/Kg.There were no significant differences in sex,age and standard body weight between the low tidal volume group and the medium tidal volume group（P>0.05）.According to the ECG monitoring system and arterial blood gas results,there were no statistically significant differences in mean arterial pressure（MAP）,arterial partial pressure of oxygen（Pa O₂）,arterial partial pressure of carbon dioxide（Pa CO₂）,lactic acid（Lac）,oxygenation index（P/F）,SOFA score,APACHEⅡscore and RASS score between the two groups（P>0.05）.Before mechanical ventilation,there were no significant differences in right heart ultrasound parameters RV-FAC,TAPSE,S’,E/A,E/e’and RV/LV between the two groups.（2）After 24 hours of mechanical ventilation,the FAC,S’and TAPSE values of patients in the moderate tidal volume group were lower than those in the low tidal volume group,and the differences were statistically significant（P<0.05）.（3）The prognostic outcome events were divided into survival or death.The patients with mechanical ventilation（163 cases）were divided into low tidal volume group（102 cases）and medium tidal volume group（61 cases）according to tidal volume.22 patients（36.07%）in the moderate tidal volume group died within 28 days.Compared with the low tidal volume group,the survival rate of patients in the moderate tidal volume group decreased,and the risk of death increased significantly（P=0.029*）.（4）After 24 hours of mechanical ventilation,a total of 29 patients（17.79%）had RVD.The tidal volume,plateau pressure and driving pressure in the RVD group were higher than those in the non-RVD group,and the difference was statistically significant（P<0.05*）.2.Effects of mechanical ventilation on right ventricular function and prognosis in patients with ARDS（1）After 24 hours of mechanical ventilation,the FAC,S’and TAPSE values of patients in the moderate tidal volume group were lower than those in the low tidal volume group,and the differences were statistically significant（P<0.05）.（2）ARDS patients with mechanical ventilation were divided into low tidal volume group（n=42）and medium tidal volume group（n=20）according to tidal volume.7 patients（16.7%）in low tidal volume group died within 28 days,and 8 patients（40%）in medium tidal volume group died within 28 days.The Kaplan-Meier survival curve showed that the survival rate of ARDS patients in the moderate tidal volume group was significantly decreased,and the risk of death was significantly increased（P=0.030）.（3）After 24 hours of mechanical ventilation,the tidal volume,plateau pressure,driving pressure,and positive end-expiratory pressure in RVD group were higher than those in non-RVD group,and the differences were statistically significant（P<0.05）.3.Effects of mechanical ventilation on right ventricular function and prognosis in non-ARDS patients（1）After 24 hours of mechanical ventilation,the TAPSE value of patients in the moderate tidal volume group was lower than that in the low tidal volume group,and the difference was statistically significant（P<0.05）.（2）In non-ARDS patients,there was no significant difference in survival rate between low tidal volume and medium tidal volume.（3）After 24 hours of mechanical ventilation,the tidal volume,plateau pressure,and driving pressure in RVD group were higher than those in non-RVD group,and the differences were statistically significant（P<0.05）.Conclusions:1.A strategy of low tidal volume（4-6ml/Kg）ventilation for 24 hours reduced the incidence of ventilator-associated right ventricular dysfunction.2.Moderate tidal volume（8-10ml/Kg）increased the risk of death,especially in patients with ARDS.3.Mechanical ventilation parameters（tidal volume,plateau pressure,driving pressure）were higher in patients with right ventricular dysfunction.