End expiratory oxygen concentrations to predict central venous oxygen saturation

An observational pilot study

Alan E. Jones, Karl R. Kuehne, Michael Steuerwald, Jeffrey Kline

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Background: A non-invasive surrogate measurement for central venous oxygen saturation (ScVO2) would be useful in the ED for assessing therapeutic interventions in critically ill patients. We hypothesized that either linear or nonlinear mathematical manipulation of the partial pressure of oxygen in breath at end expiration (EtO2) would accurately predict ScVO2. Methods: Prospective observational study of a convenience sample of hemodialysis patients age > 17 years with existing upper extremity central venous catheters were enrolled. Using a portable respiratory device, we collected both tidal breathing and end expiratory oxygen and carbon dioxide concentrations, volume and flow on each patient. Simultaneous ScVO2 measurements were obtained via blood samples collected from the hemodialysis catheter. Two models were used to predict ScVO2: 1) Best-fit multivariate linear regression equation incorporating all respiratory variables; 2) MathCAD to model the decay curve of EtO2 versus expiratory volume using the least squares method to estimate the pO2 that would occur at 2 = 0.11. The best fit multivariate equation included EtCO2 and EtO2 and when solved for ScVO2, the equation yielded a mean absolute difference from the measured ScVO2 of 8 ± 6% (range -18 to +17%). The predicted ScVO2 value was within 10% of the actual value for 57% of the patients. Modeling of the EtO2 curve did not accurately predict ScVO2 at any lung volume. Conclusion: We found no significant correlation between EtO2 and ScVO2. A linear equation incorporating EtCO2 and EtO2 had at best modest predictive Accuracy for ScVO2.

Original languageEnglish (US)
Article number9
JournalBMC Emergency Medicine
Volume6
DOIs
StatePublished - Sep 20 2006
Externally publishedYes

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Observational Studies
Oxygen
Renal Dialysis
Central Venous Catheters
Partial Pressure
Least-Squares Analysis
Critical Illness
Carbon Dioxide
Upper Extremity
Linear Models
Respiration
Catheters
Prospective Studies
Equipment and Supplies
Lung
Therapeutics

ASJC Scopus subject areas

  • Medicine(all)

Cite this

End expiratory oxygen concentrations to predict central venous oxygen saturation : An observational pilot study. / Jones, Alan E.; Kuehne, Karl R.; Steuerwald, Michael; Kline, Jeffrey.

In: BMC Emergency Medicine, Vol. 6, 9, 20.09.2006.

Research output: Contribution to journalArticle

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abstract = "Background: A non-invasive surrogate measurement for central venous oxygen saturation (ScVO2) would be useful in the ED for assessing therapeutic interventions in critically ill patients. We hypothesized that either linear or nonlinear mathematical manipulation of the partial pressure of oxygen in breath at end expiration (EtO2) would accurately predict ScVO2. Methods: Prospective observational study of a convenience sample of hemodialysis patients age > 17 years with existing upper extremity central venous catheters were enrolled. Using a portable respiratory device, we collected both tidal breathing and end expiratory oxygen and carbon dioxide concentrations, volume and flow on each patient. Simultaneous ScVO2 measurements were obtained via blood samples collected from the hemodialysis catheter. Two models were used to predict ScVO2: 1) Best-fit multivariate linear regression equation incorporating all respiratory variables; 2) MathCAD to model the decay curve of EtO2 versus expiratory volume using the least squares method to estimate the pO2 that would occur at 2 = 0.11. The best fit multivariate equation included EtCO2 and EtO2 and when solved for ScVO2, the equation yielded a mean absolute difference from the measured ScVO2 of 8 ± 6{\%} (range -18 to +17{\%}). The predicted ScVO2 value was within 10{\%} of the actual value for 57{\%} of the patients. Modeling of the EtO2 curve did not accurately predict ScVO2 at any lung volume. Conclusion: We found no significant correlation between EtO2 and ScVO2. A linear equation incorporating EtCO2 and EtO2 had at best modest predictive Accuracy for ScVO2.",
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