title: Design and representation of multivariate patient-based reference regions for arterial pH, PCO2 and base excess values.
abstract: OBJECTIVE
  To determine and compare the shape and location of three data sets of arterial pH, PCO2, and BE values from intensive care patients in a new acid-base chart for the purpose of deriving multivariate reference regions.
  
  
  METHODS
  The new chart is constructed by applying a statistical technique called principal component analysis (PCA). Three different data sets, each comprised of 1500 arterial pH, PCO2, and BE values, were subjected to PCA. The 3 data sets were collected in a respiratory intensive care unit (ICU) of a University Hospital, in a general ICU of a District Hospital, and in a neonatal ICU of a Children's Hospital.
  
  
  RESULTS
  The outlines of the resulting charts are similar for all 3 data sets, but the representations of the three distributions in the new chart are highly dissimilar, both in shape and in location.
  
  
  CONCLUSIONS
  PCA can be used to derive a patient-based reference region for arterial pH, PCO2, and BE values. Furthermore, the new chart may be useful for the graphical monitoring of acid-base data because distances between consecutive observations are faithfully represented.
authors.affiliation: Department of Medical Informatics, Erasmus University, Rotterdam, The Netherlands.
authors.forename: M
authors.initials: M
authors.lastname: Hekking
authors.forename: J
authors.initials: J
authors.lastname: Lindemans
authors.forename: E S
authors.initials: ES
authors.lastname: Gelsema
mesh_terms: D000137:Acid-Base Imbalance / Q000097:blood*; D000704:Analysis of Variance; D001158:Arteries / Q000502:physiology*; D002245:Carbon Dioxide / Q000097:blood*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007223:Infant; D007231:Infant, Newborn; D007362:Intensive Care Units; D015233:Models, Statistical; D015999:Multivariate Analysis; D012016:Reference Values
chemical_list: D002245:Carbon Dioxide