title: Intratracheal pressure monitoring during synchronized intermittent mandatory ventilation and pressure controlled-inverse ratio ventilation.
abstract: OBJECTIVE
  To directly measure airway pressures proximal and distal to endotracheal tubes during conventional synchronized intermittent mandatory ventilation (SIMV) and pressure controlled-inverse ratio ventilation (PC-IRV), and to compare them with these values measured by the ventilator.
  
  
  METHODS
  Prospective, nonrandomized study.
  
  
  METHODS
  Surgical intensive care unit at a trauma center.
  
  
  METHODS
  Group 1: Eight intubated adult patients connected to mechanical ventilators in the SIMV mode were studied. All patients required mechanical ventilation following traumatic injuries. Group 2: Five intubated adult patients with adult respiratory distress syndrome connected to mechanical ventilators were studied.
  
  
  METHODS
  A small polyethylene catheter was threaded through each endotracheal tube such that it could be positioned to measure pressures proximal and distal to the tubes.
  
  
  RESULTS
  During SIMV, a significant pressure gradient exists across endotracheal tubes. In addition, although initiation of PC-IRV did lead to a lower peak airway pressure measured proximally, intratracheal peak airway pressure was unchanged.
  
  
  CONCLUSIONS
  A pressure gradient exists during inspiration from the ventilator to the trachea in mechanically ventilated patients. Tracheal pressures cannot be predicted from proximal airway pressure monitors because of marked variation in endotracheal tube resistance in vivo. Initiation of PC-IRV does not result in a decrease in peak airway pressure when measured intratracheally.
authors.affiliation: Department of Anesthesiology, The University of Texas Medical School, Houston 77030, USA.
authors.forename: R D
authors.initials: RD
authors.lastname: Warters
authors.forename: S J
authors.initials: SJ
authors.lastname: Allen
authors.forename: A S
authors.initials: AS
authors.lastname: Tonnesen
mesh_terms: D000328:Adult; D000403:Airway Resistance; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*; D012128:Respiratory Distress Syndrome / Q000628:therapy; D014947:Wounds and Injuries / Q000628:therapy