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Prediction of Arterial Blood pH and Partial Pressure of Carbon dioxide from Venous Blood Samples in Patients Receiving Mechanical Ventilation.

Tavakol K, Ghahramanpoori B, Fararouei M - J Med Signals Sens (2013)

Bottom Line: Substitution of arterial with venous blood samples to estimate blood gas status is highly preferable due to practical and safety concerns.Results showed significant associations between arterial and venous pH and pCO2.Although highly significant correlations were found between arterial and venous blood pH and pCO2, the results did not support the reliability of prediction of arterial blood pH and pCO2 by venous blood samples across a range of concentrations.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.

ABSTRACT
Substitution of arterial with venous blood samples to estimate blood gas status is highly preferable due to practical and safety concerns. Numerous studies support the substitution of arterial by venous blood samples, reporting strong correlations between arterial and venous values. This study further investigated the predictive ability of venous blood samples for arterial Acid-Base Balance (pH) and pressure of carbon dioxide (pCO2). Participants were 51 post-brain surgery patients receiving mechanical ventilation, who had blood samples taken simultaneously from radial artery of the wrist and elbow vein. Results showed significant associations between arterial and venous pH and pCO2. However, the variation of regression residuals was not homogenous, and the regression line did not fit properly to the data, indicating that simple linear regression is sub-optimal for prediction of arterial pH and pCO2 by venous blood sample. Although highly significant correlations were found between arterial and venous blood pH and pCO2, the results did not support the reliability of prediction of arterial blood pH and pCO2 by venous blood samples across a range of concentrations.

No MeSH data available.


Related in: MedlinePlus

Correlation between arterial and venous blood gas values for pH. (Solid line represents regression line. Dotted line represents line of unity)
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Figure 1: Correlation between arterial and venous blood gas values for pH. (Solid line represents regression line. Dotted line represents line of unity)

Mentions: The associations of venous and arterial pH and pCO2 values are shown graphically and mathematically in Figures 1 and 2. The figures show lines of unity (intercept = 0, slope = 1; dotted lines), regression line (solid line), and their regression equations. Figures 3 and 4 represent the distribution of the residuals. Precision and accuracy of venous values representing arterial pH and pCO2 levels are illustrated by Bland-Altman plots [Figures 5 and 6]. The dotted lines show theoretically unbiased predictions, and the solid lines are regression lines fitted to the average and difference of arterial and venous measures to check whether differences between two measures are constant as the average of venous and arterial values increases. A horizontal regression line represents homogeneity of the differences between arterial and venous values throughout predictor variation. Figure 1 shows a strong correlation between arterial and venous pH (R2= 0.64, P < 0.001). However, the distribution of the residuals for the regression equation seems to be heterogeneous, as the correlation becomes weaker as the arterial values (dependent variable) increase [Figure 2]. Moreover, the significant association between residuals and arterial values (P < 0.001) suggests that a linear regression model is sub-optimal for prediction of arterial pH across the observed range of measurements. Differences between arterial and venous values against their averages suggest that venous values are predominantly less than arterial levels and the differences get closer to as the average values increase [Figure 3].


Prediction of Arterial Blood pH and Partial Pressure of Carbon dioxide from Venous Blood Samples in Patients Receiving Mechanical Ventilation.

Tavakol K, Ghahramanpoori B, Fararouei M - J Med Signals Sens (2013)

Correlation between arterial and venous blood gas values for pH. (Solid line represents regression line. Dotted line represents line of unity)
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3959008&req=5

Figure 1: Correlation between arterial and venous blood gas values for pH. (Solid line represents regression line. Dotted line represents line of unity)
Mentions: The associations of venous and arterial pH and pCO2 values are shown graphically and mathematically in Figures 1 and 2. The figures show lines of unity (intercept = 0, slope = 1; dotted lines), regression line (solid line), and their regression equations. Figures 3 and 4 represent the distribution of the residuals. Precision and accuracy of venous values representing arterial pH and pCO2 levels are illustrated by Bland-Altman plots [Figures 5 and 6]. The dotted lines show theoretically unbiased predictions, and the solid lines are regression lines fitted to the average and difference of arterial and venous measures to check whether differences between two measures are constant as the average of venous and arterial values increases. A horizontal regression line represents homogeneity of the differences between arterial and venous values throughout predictor variation. Figure 1 shows a strong correlation between arterial and venous pH (R2= 0.64, P < 0.001). However, the distribution of the residuals for the regression equation seems to be heterogeneous, as the correlation becomes weaker as the arterial values (dependent variable) increase [Figure 2]. Moreover, the significant association between residuals and arterial values (P < 0.001) suggests that a linear regression model is sub-optimal for prediction of arterial pH across the observed range of measurements. Differences between arterial and venous values against their averages suggest that venous values are predominantly less than arterial levels and the differences get closer to as the average values increase [Figure 3].

Bottom Line: Substitution of arterial with venous blood samples to estimate blood gas status is highly preferable due to practical and safety concerns.Results showed significant associations between arterial and venous pH and pCO2.Although highly significant correlations were found between arterial and venous blood pH and pCO2, the results did not support the reliability of prediction of arterial blood pH and pCO2 by venous blood samples across a range of concentrations.

View Article: PubMed Central - PubMed

Affiliation: Department of Anesthesiology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.

ABSTRACT
Substitution of arterial with venous blood samples to estimate blood gas status is highly preferable due to practical and safety concerns. Numerous studies support the substitution of arterial by venous blood samples, reporting strong correlations between arterial and venous values. This study further investigated the predictive ability of venous blood samples for arterial Acid-Base Balance (pH) and pressure of carbon dioxide (pCO2). Participants were 51 post-brain surgery patients receiving mechanical ventilation, who had blood samples taken simultaneously from radial artery of the wrist and elbow vein. Results showed significant associations between arterial and venous pH and pCO2. However, the variation of regression residuals was not homogenous, and the regression line did not fit properly to the data, indicating that simple linear regression is sub-optimal for prediction of arterial pH and pCO2 by venous blood sample. Although highly significant correlations were found between arterial and venous blood pH and pCO2, the results did not support the reliability of prediction of arterial blood pH and pCO2 by venous blood samples across a range of concentrations.

No MeSH data available.


Related in: MedlinePlus