title: Improvement in accuracy of transcutaneous measurement of oxygen with resumption of spontaneous ventilation in mechanically ventilated patients after off pump coronary artery bypass procedure: a prospective study.
abstract: BACKGROUND
  Transcutaneous measurement of gases depends on the degree of skin perfusion. Mechanical ventilation causes alteration in the peripheral perfusion. The aim of this prospective observational study was to assess change in the accuracy of interchangeability of arterial blood gases with those obtained transcutaneously at various phases of mechanical ventilation such as controlled mandatory, synchronized intermittent mandatory, continuous positive airway pressure ventilations, spontaneous breathing trail and spontaneous ventilation after extubation of endotracheal tube.
  
  
  METHODS
  Thirty-two adult patients who underwent uncomplicated off pump coronary artery bypass surgery in a tertiary care medical center were subjected to transcutaneous measurements of gases from the sensor placed on the chest during postoperative ventilation. Arterial blood gas analysis was performed at predetermined time intervals and transcutaneous measurements were repeated each of those time.
  
  
  RESULTS
  Fifty-four sets of data were obtained during controlled ventilation and fifty during spontaneous. Correlation coefficient for oxygen increased from 0.46 (P = 0.0004) during controlled ventilation to 0.75 (P < 0.0001) during spontaneous. Bland-Altman and mountain plots suggested better inter- changeability of values between arterial blood gas and transcutaneous gas monitoring. The bias for oxygen changed from 21 during controlled ventilation to 25 during spontaneous ventilation and the precision from 7.1 to 6.4. There was no change in the accuracy of transcutaneous carbon dioxide values during either phase of ventilation.
  
  
  CONCLUSIONS
  The accuracy of transcutaneously measured values of oxygen improved significantly during spontaneous ventilation.
authors.affiliation: Wockhardt Hospitals, Mumbai, India. mailchakravarthy@gmail.com
authors.forename: Murali
authors.initials: M
authors.lastname: Chakravarthy
authors.forename: Sandeep
authors.initials: S
authors.lastname: Narayan
authors.forename: Raghav
authors.initials: R
authors.lastname: Govindarajan
authors.forename: Vivek
authors.initials: V
authors.lastname: Jawali
mesh_terms: D000328:Adult; D001785:Blood Gas Monitoring, Transcutaneous / Q000379:methods* / Q000592:standards*; D002245:Carbon Dioxide / Q000097:blood; D047549:Coronary Artery Bypass, Off-Pump; D003627:Data Interpretation, Statistical; D006801:Humans; D010100:Oxygen / Q000097:blood; D011182:Postoperative Care; D011446:Prospective Studies; D012121:Respiration, Artificial / Q000379:methods*; D012189:Retrospective Studies
chemical_list: D002245:Carbon Dioxide; D010100:Oxygen