title: A new oxygenation index for reflecting intrapulmonary shunting in patients undergoing open-heart surgery.
abstract: OBJECTIVE
  To assess the reliability of new and traditional oxygenation measurements in reflecting intrapulmonary shunt.
  
  
  METHODS
  Prospective study.
  
  
  METHODS
  Cardiac surgery unit at a university hospital.
  
  
  METHODS
  Fifty-five patients undergoing coronary artery bypass grafting.
  
  
  RESULTS
  Simultaneous blood samples were collected from an indwelling arterial line and a catheter for determination of blood gases. Standard accepted formulas were utilized to measure a new oxygenation index: PaO(2)/fraction of inspired oxygen (FIO(2)) x mean airway pressure (Paw). The standard formulas used were the oxygenation ratio (PaO(2)/FIO(2)), PaO(2)/alveolar partial oxygen pressure (PAO(2)), alveolar-arterial oxygen tension gradient (P[A-a]O(2)), and intrapulmonary shunt (venous admixture [Qsp/Qt]). There were significant negative (p < 0.05) correlations between the PaO(2)/(FIO(2) x Paw) and Qsp/Qt (r = - 0.85), between the PaO(2)/FIO(2) and Qsp/Qt (r = - 0.74), and between the PaO(2)/PAO(2) and Qsp/Qt (r = - 0.71). There was a significant positive (p < 0.05) correlation between the P(A-a)O(2) gradient and Qsp/Qt (r = 0.66). However, the correlation was strongest between the PaO(2)/(FIO(2) x Paw) and Qsp/Qt.
  
  
  CONCLUSIONS
  In this group of patients, PaO(2)/(FIO(2) x Paw) might be more reliable than other oxygenation measurements in reflecting intrapulmonary shunt.
authors.affiliation: Department of Anesthesiology, School of Medicine, American University of Beirut, PO Box 11-0236, Riad El Solh, Beirut 1107 2020, Lebanon. mk05@aub.edu.lb
authors.forename: Mohamad F
authors.initials: MF
authors.lastname: El-Khatib
authors.forename: Ghassan W
authors.initials: GW
authors.lastname: Jamaleddine
mesh_terms: D000222:Adaptation, Physiological; D000368:Aged; D001784:Blood Gas Analysis; D002245:Carbon Dioxide / Q000097:blood*; D001026:Coronary Artery Bypass / Q000379:methods*; D003327:Coronary Disease / Q000175:diagnosis / Q000601:surgery*; D005260:Female; D005500:Follow-Up Studies; D006785:Hospitals, University; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative; D010092:Oximetry; D011175:Positive-Pressure Respiration; D011182:Postoperative Care / Q000379:methods; D011336:Probability; D011446:Prospective Studies; D011652:Pulmonary Circulation / Q000502:physiology*; D011659:Pulmonary Gas Exchange / Q000502:physiology*; D012129:Respiratory Function Tests; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D002245:Carbon Dioxide