OBI Medical

v-TAC precision kPa

v-TAC software calculates arterial acid-base and blood gas values from venous blood with an accuracy and precision in clinical practice comparable to arterial blood gas.

Precision of the v-TAC method is calculated based on data from several clinical studies* collected from emergency departments, pulmonary departments and intensive care units.

How is v-TAC precision measured?

A v-TAC measurement (arterial values calculated from a venous blood sample and a SpO2 measurement using the v-TAC method) is compared to arterial blood gas (ABG) as the gold reference. The two measurements are measured simultaneously. 

Table-1 below show the statistical variation of the v-TAC calculated arterial blood gas vs the reference arterial blood gas measurement.

Comments to the precision table-1:

  1. v-TAC vs ABG as reference. v-TAC includes effect from variation in SpO2 measurement and all other sources of errors, such as pre-analytical errors.
  2. pO2 variation not normal distributed

v-TAC precision plots for pH

Plots comparing pH for v-TAC vs. arterial (ABG1) shown as black dots, with arterial (ABG12) vs. arterial (ABG21) repeatability shown as red dots.

v-TAC precision plots for pCO2 in [kPa]

Plots comparing pCO2 for v-TAC vs. arterial (ABG1) shown as black dots, with arterial (ABG2) vs. arterial (ABG1) repeatability shown as red dots.

v-TAC precision plot for pO2 in [kPa]

Plots comparing pO2 for v-TAC vs. arterial (ABG1) shown as black dots, with arterial (ABG2) vs. arterial (ABG1) repeatability shown as red dots.

* Studies:

- Tygesen G et all;  Mathematical arterialisation of venous blood in emergency medicine patients. (Group B excluded due to 15 minutes between sample pairs)

- M. Toftegaard et all; Evaluation of a method for converting venous values of acid-base and oxygenation status to arterial values. 

- S.E. Rees et all; Converting venous acid-base and oxygen status to arterial in patients with lung disease. 

- S.E. Rees et all; Correlation between acid-base parameters measured in arterial blood and venous blood samples peripherally, from vena cavae superior, and from the pulmonary artery. 

- S.E. Rees et all; A method for calculation of arterial acid-base and blood gas status from measurements in the peripheral venous blood. 

- v-TAC study, Klinikum Fürth

- v-TAC study, Aintree