Relationship between partial carbon dioxide pressure and strong ions in humans: A retrospective study

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Little is known about the role of a strong ions in humans with respiratory abnormalities. In this study, we investigated the associations between partial carbon dioxide pressure (pCO2) and each of sodium ion (Na+) concentrations, chloride ion (Cl-) concentrations and their difference (SIDNa-Cl). Blood gas data were obtained from patients in a teaching hospital intensive care unit between August 2013 and January 2017. The association between pCO2 and SIDNa-Cl was defined as the primary outcome. The associations between pCO2 and [Cl-], [Na+] and other strong ions were secondary outcomes. pCO2 was stratified into 10 mmHg-wide bands and treated as a categorical variable for comparison. As a result, we reviewed 115,936 blood gas data points from 3,840 different ICU stays. There were significant differences in SIDNa-Cl, [Cl-], and [Na+] among all categorized pCO2 bands. The respective pCO2 SIDNa-Cl, [Cl-], and [Na+] correlation coefficients were 0.48,-0.31, and 0.08. SIDNa-Cl increased and [Cl-] decreased with pCO2, with little relationship between pCO2 and [Na+] across subsets. In conclusion, we found relatively strong correlations between pCO2 and SIDNa-Cl in the multiple blood gas datasets examined. Correlations between pCO2 and chloride concentrations, but not sodium concentrations, were further found to be moderate in these ICU data.

Original languageEnglish
Pages (from-to)319-325
Number of pages7
JournalActa medica Okayama
Issue number4
Publication statusPublished - 2020


  • Acid-base phenomena
  • Chlorine ion
  • Partial carbon dioxide pressure
  • Stewart approach
  • Strong ion difference

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)


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