title: [The influence of positive end-expiratory pressure on cerebral blood flow and cerebrovascular autoregulation in patients with acute respiratory distress syndrome].
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: 324.7±117.2 mmHg vs. 173.4±95.8 mmHg, t=5.913, P=0.000; PIP: 34.7±9.1 cmH2O vs. 26.1±7.9 cmH2O,t=4.222, P=0.000; Pplat: 30.5±8.4 cmH2O vs. 22.2±7.1 cmH2O, t=4.465, P=0.000; CVP: 12.1±3.5 mmHg vs. 8.8±2.2 mmHg, 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 (85.5±19.1 beats/min vs. 82.7±17.3 beats/min, t=0.643, P=0.523), mean arterial pressure (73.5±12.4 mmHg vs. 76.4±15.1 mmHg, t=0.878, P=0.383) and CBF velocity of MCA [peak systolic flow velocity (Vmax): 91.26±17.57 cm/s vs. 96.64±18.71 cm/s, t=1.240, P=0.219; diastolic flow velocity (Vmin): 31.54±7.71 cm/s vs. 33.87±8.53 cm/s, t=1.199, P=0.235; mean velocity (Vmean): 51.19±12.05 cm/s vs. 54.27±13.36 cm/s, 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.
authors.affiliation: Department of Critical Care Medicine, People's Hospital of Jiangxi Province, Nanchang 330006, Jiangxi, China. Corresponding author: Chen Zhi, Email: jxcz120@qq.com.
authors.forename: Chunli
authors.initials: C
authors.lastname: Yang
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.forename: Yuanhua
authors.initials: Y
authors.lastname: Lu
authors.forename: Huiwei
authors.initials: H
authors.lastname: He
authors.forename: Weihua
authors.initials: W
authors.lastname: Zeng
mesh_terms: D000328:Adult; D000368:Aged; D002560:Cerebrovascular Circulation / Q000502:physiology*; D005260:Female; D006439:Hemodynamics; D006706:Homeostasis; D006801:Humans; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000503:physiopathology*