title: Time required for equilibration of arterial oxygen pressure after setting optimal positive end-expiratory pressure in acute respiratory distress syndrome.
abstract: OBJECTIVE
  To evaluate the time course of Pao2 change following the setting of optimal positive end-expiratory pressure (PEEP) in patients with acute respiratory distress syndrome (ARDS).
  
  
  METHODS
  Prospective clinical study.
  
  
  METHODS
  Multidisciplinary intensive care unit of a university hospital.
  
  
  METHODS
  Twenty-five consecutive patients with ARDS.
  
  
  METHODS
  ARDS was diagnosed during pressure-regulated volume control ventilation with tidal volume of 7 mL/kg actual body weight, respiratory rate of 12 breaths/min, inspiratory/expiratory ratio of 1:2, Fio2 of 1, and PEEP of 5 cm H2O. A critical care attending physician obtained pressure volume curves and determined the lower inflection point. Following a rest period of 30 mins with initial ventilation variables, PEEP was set at 2 cm H2O above the lower inflection point, and serial blood samples were collected during 1-hr ventilation with optimal PEEP. Arterial blood gas analyses were performed at 1, 3, 5, 7, 9, 11, 15, 20, 30, 45, and 60 mins.
  
  
  RESULTS
  Twenty-five patients were found eligible for the study. Three patients were excluded due to deterioration of oxygen saturation and hemodynamic instability following the initiation of optimal PEEP. Eight cases (36%) were considered to be of pulmonary origin and 14 cases (64%) of extrapulmonary origin. Optimal PEEP levels were 14 +/- 3 cm H2O and 14 +/- 4 cm H2O in pulmonary and extrapulmonary ARDS, respectively. Pao2 demonstrated a 130 +/- 101% increase at the end of 1-hr period in total study population. This improvement did not differ significantly between pulmonary and extrapulmonary forms of ARDS (135 +/- 118% vs. 127 +/- 95%, p = .8). Mean 90% oxygenation time was found to be 20 +/- 19 mins. In the subset of patients with ARDS of pulmonary origin, 90% oxygenation time was 25 +/- 26 mins, whereas it was 17 +/- 15 mins in patients with ARDS of extrapulmonary origin (p = .8).
  
  
  CONCLUSIONS
  Our data showed that 20 mins would be adequate for obtaining a blood gas sample in ARDS patients with pulmonary and extrapulmonary origin after application of optimal PEEP 2 cm H2O above the lower inflection point.
authors.affiliation: Department of Anesthesiology, Istanbul Medical Faculty, Istanbul, Turkey.
authors.forename: Simru
authors.initials: S
authors.lastname: Tugrul
authors.forename: Nahit
authors.initials: N
authors.lastname: Cakar
authors.forename: Ozkan
authors.initials: O
authors.lastname: Akinci
authors.forename: Perihan Ergin
authors.initials: PE
authors.lastname: Ozcan
authors.forename: Rian
authors.initials: R
authors.lastname: Disci
authors.forename: Figen
authors.initials: F
authors.lastname: Esen
authors.forename: Lutfi
authors.initials: L
authors.lastname: Telci
authors.forename: Kutay
authors.initials: K
authors.lastname: Akpir
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D010100:Oxygen / Q000097:blood*; D011175:Positive-Pressure Respiration / Q000379:methods*; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000628:therapy*; D013997:Time Factors
chemical_list: D010100:Oxygen