title: Gastric intramucosal pH is stable during titration of positive end-expiratory pressure to improve oxygenation in acute respiratory distress syndrome.
abstract: BACKGROUND
  Optimal positive end-expiratory pressure (PEEP) is an important component of adequate mechanical ventilation in acute lung injury and acute respiratory distress syndrome (ARDS). In the present study we tested the effect on gastric intramucosal pH of incremental increases in PEEP level (i.e. PEEP titration) to improve oxygenation in ARDS. Seventeen consecutive patients with ARDS, as defined by consensus criteria, were included in this clinical, prospective study. All patients were haemodynamically stable, and were not receiving vasopressors. From an initial level of 5 cmH2O, PEEP was titrated at 2 cmH2O increments until the partial arterial oxygen tension was 300 mmHg or greater, peak airway pressure was 45 cmH2O or greater, or mean arterial blood pressure decreased by 20% or more of the baseline value. Optimal PEEP was defined as the level of PEEP that achieved the best oxygenation. The maximum PEEP was the highest PEEP level reached during titration in each patient.
  
  
  RESULTS
  Gastric mucosal pH was measured using gastric tonometry at all levels of PEEP. The thermodilution technique was used for measurement of cardiac index. Gastric mucosal pH was similar at baseline and at optimal PEEP levels, but it was slightly reduced at maximum PEEP. Cardiac index and oxygen delivery remained stable at all PEEP levels.
  
  
  CONCLUSIONS
  Incremental titration of PEEP based on improvement in oxygenation does not decrease gastric intramucosal perfusion when cardiac output is preserved in patients with ARDS.
authors.affiliation: Department of Anesthesiology and Intensive Care, Istanbul Medical Faculty, Capa Klinikleri, Istanbul, Turkey. iozkana@yahoo.com
authors.forename: Ibrahim Ozkan
authors.initials: IO
authors.lastname: Akinci
authors.forename: Nahit
authors.initials: N
authors.lastname: Cakar
authors.forename: Gökhan Mehmet
authors.initials: GM
authors.lastname: Mutlu
authors.forename: Simru
authors.initials: S
authors.lastname: Tugrul
authors.forename: Perihan Ergin
authors.initials: PE
authors.lastname: Ozcan
authors.forename: Musa
authors.initials: M
authors.lastname: Gitmez
authors.forename: Figen
authors.initials: F
authors.lastname: Esen
authors.forename: Lutfi
authors.initials: L
authors.lastname: Telci
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D001784:Blood Gas Analysis; D005260:Female; D005753:Gastric Mucosa / Q000378:metabolism*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000378:metabolism / Q000628:therapy*; D017186:Titrimetry / Q000379:methods*