Prognostic Value Of The Of Thepulmonary Dead-space Fraction In Patients Of Acute Respiratory Distress Syndrome

Objective:To investigate the pulmonary dead-space fraction on the prognosis of acute respiratory distress syndrome(ARDS).Methods:32 patients meeting ARDS Berlin definition,who were admitted to the EICU from January 2015 to August 2016,were analyzed with a prospective method.The VD/VT was measured by the single breath test of CO2(day6 from day 1).VD/VT were obtained based upon a prediction equation validated by Frankenfield et al for dead spce ventilation fraction:VD/VT = 0.320+0.0106(PaCO2-ETC02)+0.003(RR)+0.0015(Age).Patient general condition,vital signs,APACHE II,LIPS,PaO2/FiO2、PvCO2、PEEP,aurway plateau pressure(Plat),28-day mortality were recorded.The patients were divided into a survival group and a death group according to their survival situation in 28 days.Results:Camparison of VD/VT between the death group and the survival group of ARDS patients at different time point:VD/VT was elvated in the two groups.VD/VT showed no statistical differencefrom the 1 stday to the 3th day after admission.But higher in the death group from the 4th day to the 6th day after admission(P<0.01).VD/VT was significantly higher in nonsurvivors than in survivors from the 4th day of mechanical ventilation.The comparison of the dynamic changes of VD/VT with in the two groups:the VD/VT in the death group increased gradually from 1 st day to 6th day(P<0.001),but that changing trend in the survival group showed no statistical difference.△VD/VT was independent risk factors of patients 28 day prognosis(P<0.05).ROC curveand28-day snrvival curve showed that the area under ROC curve of VD/VT predicting prognosis of patientswith ARDS was 0.961.When the optimal cut off value was 0.62,the sensitivity was 0.900,and specificity was 0.955,significantly higher than 1d、5d、6d.ROC curveand 28-day survival curve also showed that the area under ROC curve of VD/VT predicting prognosis of patientswith ARDS was 0.910,higher than APACHE Ⅱ and LIPS.When the optimal cut off value was 0.62,the sensitivity was 0.916,and specificity was 0.955.Conclusions:Fourth day dead space fraction has guiding value for prognosis evaluation,Compared with APACHE score,LIPS score,dead space fraction is more instructive to the prognosis of ARDS patients.