The influence of positive end-expiratory pressure on cerebral blood flow and cerebrovascular autoregulation in patients with acute respiratory distress syndrome / 中华危重病急救医学

ABSTRACT

Objective To explore the influence of different positive end-expiratory pressure (PEEP) levels on cerebral blood flow (CBF) and cerebrovascular autoregulation in patients with acute respiratory distress syndrome (ARDS).Methods A prospective study was conducted.Moderate or severe ARDS patients admitted to Department of Critical Care Medicine of Jiangxi Provincial People's Hospital from January 1st,2013 to October 1st,2013 were enrolled.The changes in hemodynamics,respiratory mechanics and gas exchange under different levels of PEEP were observed.CBF velocity of middle cerebral artery (MCA) was measured using transcranial Doppler (TCD),and breath-holding index (BHI) was also calculated.Results 35 patients with ARDS were included.The oxygenation index (OI),peak inspiratory pressure (PIP),plat pressure (Pplat) and central venous pressure (CVP) were markedly elevated [OI (mmHg,1 mmHg=0.133 kPa)324.7± 117.2 vs.173.4± 95.8,t=5.913,P=0.000; PIP (cmH2O)34.7 ± 9.1 vs.26.1 ± 7.9,t=4.222,P=0.000; Pplat (cmH2O)30.5 ± 8.4 vs.22.2 ± 7.1,t=4.465,P=0.000; CVP (mmHg)12.1 ± 3.5 vs.8.8 ± 2.2,t=4.723,P=0.000] when PEEP was increased from (6.4 ± 1.0) cmH2O to (14.5-± 2.0) cmH2O (1 cmH2O=0.098 kPa).But no significant difference in the heart rate (beats/min85.5 ± 19.1 vs.82.7 ± 17.3,t=0.643,P=0.523),mean arterial pressure (mmHg73.5 ± 12.4 vs.76.4 ± 15.1,t=0.878,P=0.383) and CBF velocity of MCA [peak systohc flow velocity (Vmax,cm/s)91.26 ± 17.57 vs.96.64 ± 18.71,t=1.240,P=0.219; diastolic flow velocity (Vmin,cm/s) 31.54 ±7.71 vs.33.87 ±8.53,t=1.199,P=0.235; mean velocity (Vmean,cm/s) 51.19 ± 12.05 vs.54.27 ± 13.36,t=1.013,P=0.315] was found.18 patients with BHI＜0.1 at baseline demonstrated that cerebral vasomotor reactivity was poor.BHI was slightly decreased with increase in PEEP (0.78 ± 0.16 vs.0.86 ± 0.19,t=1.905,P=0.061).Conclusions Some of moderate or severe ARDS patients without central nervous system disease have independent of preexisting cerebral autoregulation impairment.However,independent of preexisting cerebral autoregulation may not further be impaired when a high PEEP was chosen.