title: Evaluation of Masimo signal extraction technology pulse oximetry in anaesthetized pregnant sheep.
abstract: OBJECTIVE
  Evaluation of the accuracy of Masimo signal extraction technology (SET) pulse oximetry in anaesthetized late gestational pregnant sheep.
  
  
  METHODS
  Prospective experimental study.
  
  
  METHODS
  Seventeen pregnant Merino ewes.
  
  
  METHODS
  Animals included in study were late gestation ewes undergoing general anaesthesia for Caesarean delivery or foetal surgery in a medical research laboratory. Masimo Radical-7 pulse oximetry (SpO(2) ) measurements were compared to co-oximetry (SaO(2) ) measurements from arterial blood gas analyses. The failure rate of the pulse oximeter was calculated. Accuracy was assessed by Bland & Altman's (2007) limits of agreement method. The effect of mean arterial blood pressure (MAP), perfusion index (PI) and haemoglobin (Hb) concentration on accuracy were assessed by regression analysis.
  
  
  RESULTS
  Forty arterial blood samples paired with SpO(2) and blood pressure measurements were obtained. SpO(2) ranged from 42 to 99% and SaO(2) from 43.7 to 99.9%. MAP ranged from 24 to 82 mmHg, PI from 0.1 to 1.56 and Hb concentration from 71 to 114 g L(-1) . Masimo pulse oximetry measurements tended to underestimate oxyhaemoglobin saturation compared to co-oximetry with a bias (mean difference) of -2% and precision (standard deviation of the differences) of 6%. Accuracy appeared to decrease when SpO(2) was <75%, however numbers were too small for statistical comparisons. Hb concentration and PI had no significant effect on accuracy, whereas MAP was negatively correlated with SpO(2) bias.
  
  
  CONCLUSIONS
  Masimo SET pulse oximetry can provide reliable and continuous monitoring of arterial oxyhaemoglobin saturation in anaesthetized pregnant sheep during clinically relevant levels of cardiopulmonary dysfunction. Further work is needed to assess pulse oximeter function during extreme hypotension and hypoxaemia.
authors.affiliation: Division of Veterinary and Biomedical Sciences, Murdoch University, Perth, WA, Australia. cquinn@csu.edu.au
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Quinn
authors.forename: Anthea L
authors.initials: AL
authors.lastname: Raisis
authors.forename: Gabrielle C
authors.initials: GC
authors.lastname: Musk
mesh_terms: D000768:Anesthesia, General / Q000662:veterinary*; D000818:Animals; D005260:Female; D010092:Oximetry / Q000295:instrumentation / Q000662:veterinary*; D011247:Pregnancy; D012756:Sheep / Q000502:physiology*