A Clinical Research Of Positive Endexpiratory Pressure Influencing On Tidal Recruitment/Derecruitment In Patients With Moderate And Severe ARDS

Part one Effects of positive end-expiratory pressure on alveolar tidal recruitment/derecruitment in patients with moderate or severe acute respiratory distress syndromeObjective: To evaluate the effects of positive end-expiratory pressure(PEEP)on tidal recruitment/derecruitment in patients with moderate and severe ARDS.Methods: This was a prospective observational clinical study.Patients with moderate and severe ARDS(Pa O2/Fi O2< 200 mm Hg)were enrolled.According to ARDS net Fi O2/PEEP table,PEEP was set to PEEP(PEEPR)and high PEEP(PEEPH).Electrical impedance was recorded by electronic impedance tomography(EIT).Ventilation distribution was evaluated by△Z%,global inhomogeneity(GI),recruitable alveloar collapse and hyperinflation percentage,regional ventilation delay inhomogeneity(RVDI).Respiratory mechanics parameters and gas exchange parameters were recorded.Results: Twenty patients are enrolled.Compared with PEEPR,ventilation distribution increased in dependent lung region and decreased in independent lung region in ARDS patients significantly at PEEPH(P<0.05),but GI didn’t decrease significantly.Recruitable alveloar collapse decreased and hyperinflation increased in the global lung and in separate regions of intrest(ROI1-4 from sternum to vertebrae)significantly(P<0.05).But tidal recruitment/ derecruitment didn’t decrease globally and in ROI 1-4.Conclusion:High PEEP strategy could improve ventilation distribution of dependant lung in ARDS patients,but couldn’t decrease tidal recruitment/derecruitment.Part two Effects of positive end-expiratory pressure on alveolar tidal recruitment/ derecruitment in acute respiratory distress syndrome patients with different lung recruitbility.Objective: To evaluate the effects of PEEP on tidal recruitment/ derecruitment in ARDS patients with different lung recruitbility.Methods: This was a prospective observational study.Patients with moderate and severe ARDS(Pa O2/Fi O2<200mm Hg)were enrolled.PEEP decremental titration method was used to evaluate lung recruitbility.Lung recruitbility was calculated by electrical impedance.ARDS patients were divided to non-recruitable and recruitable group with the median of lung recruitbility.According to ARDS net Fi O2/PEEP table,PEEP was set to PEEP(PEEPR)and high PEEP(PEEPH).Electrical impedance was recorded by EIT.Ventilation distribution was evaluated by△Z%,GI,recruitable alveloar collapse and hyperinflation percentage,RVDI.Respiratory mechanics parameters and gas exchange parameters were recorded.Results: There were 10 patients in non-recruitable and recruitable group separately.When PEEP was set at PEEPR or PEEPH,there was no significant difference in ventilation distribution in dependent lung and independent lung,recruitable alveloar collapse and hyperinflation percentage between non-recruitable and recruitable group(P>0.05).Compared with PEEPR,ventilation distribution increased in dependent lung and recruitable alveloar collapse decreased significantly in non-recruitable and recruitable group at PEEPH.Compared with PEEPR,ventilation distribution decreased in independent lung and hyperinflation significantly increased in non-recruitable and recruitable group at PEEPH.Compared with non-recruitable group,tidal recruitment/ derecruitment in ROI4 was significantly lower in recruitable group at PEEPH.Compared with PEEPR,tidal recruitment/ derecruitment didn’t change globally and in ROI1-4 in non-recruitable and recruitable group.Conclusion:High PEEP strategy could improve ventilation distribution both in non-recruitable and recruitable group,but it could only decrease tidal recruitment/derecruitment in the dorsol part of ARDS patients in recruitable group.