v-TAC Standalone software

IVD For in vitro diagnostic use.
v-TAC Standalone software
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Calculating Arterial Blood Gas values using venous blood samples

v-TAC Standalone is an in vitro diagnostic medical device software that offers an alternative to the conventional Arterial Blood Gas (ABG) testing, which is well known for being painful for the patients and complex to perform.

The v-TAC software is intended to automatically calculate ABG values based on peripheral venous blood gas measurements and an arterial oxygen saturation (SpO2) value measured by pulse oximetry.

The v-TAC software arterializes peripheral venous blood gas values by mathematically adding O2 and removing CO2 using advanced physiological acid-base and oxygenation models until the calculated oxygen saturation equals the arterial oxygenation (SpO2) measured by pulse oximetry.

Operating with v-TAC in daily clinical practice is simple due to the seamless integration of the software with existing blood gas analyzers. No interaction with the software is needed.

v-TAC software has been validated in several studies, and results suggest it may help replace arterial blood gas testing.1

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Benefits at a glance

Benefits at a glance

v-TAC supports proper diagnosis and decision making based on venous blood gas samples and pulse oximetry. The operational workflow is as follows:

  • Measure the arterial oxygen saturation (SpO2) using a pulse oximeter.
  • Draw an anaerobic peripheral venous blood sample using a needle or vacutainer holder, a butterfly, or a peripheral venous catheter.
  • To start the analysis, insert the venous blood sample into the blood gas analyzer and manually enter the measured SpO2 value. The exact operation of the blood gas analyzer depends on the analyzer brand and type.
  • v-TAC Standalone delivers calculated arterial blood gas values that instantly become available on a printed report (optional) and in the electronic patient record.10

Reduce patient pain and the risk of side effects by avoiding arterial punctures.

Patient screening in the emergency department

The blood sample for venous blood gas can be drawn in combination with other regular blood tests, thus obviating arterial punctures and reducing time to care while not compromising the quality of information gained.2

Blood gas testing in cardio-respiratory and other wards:

Using venous blood and v-TAC may ease access to blood gas testing when arterial punctures are problematic or qualified resources are unavailable or limited. v-TAC can enable a task transfer from medical doctors to other staff groups, such as nurses, which may improve workflow in the wards. v-TAC can enhance nurse autonomy and upscale nurse-led care, where nurses take over more responsibility. This may improve compliance with guidelines and outcomes and reduce length-of-stay.3

Monitoring of patients' response to treatment:

v-TAC can reduce the need for repeated arterial punctures, frequent in certain treatments such as Non-Invasive Ventilation (NIV), and may improve timely monitoring of this patient group.2-4,7

Reducing the use of arterial lines in the intensive care unit:

v-TAC may reduce the use of arterial lines and thereby may reduce the risk of well-known side effects such as injuries to the arteries.5 By reducing the use of arterial lines, v-TAC may contribute to improved patient mobility.6

Save doctors' time and allow other trained staff, like nurses, to obtain calculated ABG values from venous blood.

  • In many countries, arterial blood gas sampling is only conducted by doctors, which may pose a limitation when resources are scarce and patients need a quick diagnosis. In this way, as only venous blood is needed, v-TAC enables the transfer of blood gas testing tasks from doctors to nurses and other trained staff who are allowed to collect venous blood.
  • Additionally, as v-TAC offers an easier way to get access to ABG values, it reduces the need for separate arterial punctures. The blood sample for venous blood gas can be drawn in combination with other regular blood tests, thus obviating arterial punctures and reducing time to care while not compromising the quality of information gained.2
  • This is a great benefit for the screening of patients in the Emergency Department. v-TAC values have accuracy close to that of repeated arterial blood gas measurements.

Avoid time-consuming and complex arterial punctures and allow a wider number of healthcare professionals to perform blood gas testing.

  • A study from 2023 found that the blood sample failure for venous (v-TAC) blood was 2% compared to 13% for arterial and 21% for capillary sampling.7
  • pO2 values cannot be obtained from venous blood, therefore, VBGs cannot be used for assessing the oxygenation status of patients. v-TAC calculated pO2 is a good alternative to pO2 measured in arterial blood.
  • Venous pCO2 is a poor substitute for arterial pCO2, but v-TAC estimates arterial pCO2 from peripheral venous blood, which closely aligns with arterial measured pCO2, as could be shown by multiple independent clinical studies.
  • v-TAC is able to detect trends in pCO2 values more accurately than venous pCO2, which has been shown to lack accuracy for trending.8
  • When using v-TAC, only 2.4% of the pCO2 trending points were outside the limits of 5mmHg compared to arterial blood, but still within a difference of 7.5mmHg, whereas, for venous blood alone, 26.8% were outside the limits of 5mmHg, 4.9% even outside 10mmHg, and some of these more extensively.8

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Key product features

Benefits of v-TAC in clinical settings
Benefits of v-TAC in clinical settings

Explore the applications and potential benefits of v-TAC software in different clinical settings.

Explore the applications and potential benefits of v-TAC software in different clinical settings.
v-TAC accurately trends arterial pCO28
v-TAC accurately trends arterial pCO28

See how venous blood and v-TAC can monitor pCO2 trends and understand the limitations of using venous blood alone.

See how venous blood and v-TAC can monitor pCO2 trends and understand the limitations of using venous blood alone.
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    Frequently asked questions

    Frequently asked questions

    The v-TAC software and method is based on research from Aalborg University, Denmark. The following three publications explain the background of the v-TAC software.

    • Rees SE et al. (2010). Mathematical modeling of the acid-base chemistry and oxygenation of blood: a mass balance, mass action approach including plasma and red blood cells. Eur J Appl Physiol 108:483-494. doi:10.1007/s00421-009-1244-x
    • Rees SE et al. (2006). A method for calculation of arterial acid-base and blood gas status from measurements in the peripheral venous blood. Comput Meth Prog Bio 81(1):18-25. doi:10.1016/j.cmpb.2005.10.003
    • Rees SE, Andreassen S. (2005). Mathematical models of oxygen and carbon dioxide storage and transport: The acid-base chemistry of blood. Crit Rev Biomed Eng 33(3):209-264. doi: 10.1615/CritRevBiomedEng.v33.i3.10

    Multiple studies have evaluated v-TAC performance by comparing v-TAC calculated arterial values with the gold standard arterial blood gas. Some studies also collected a second arterial sample (ABG2) immediately after the VBG sample. The purpose was to evaluate the repeatability of arterial blood gases in clinical practice.

    The study population included a broad range of patients from emergency departments, pulmonary departments, and intensive care units with various diagnoses, including COPD, sepsis, asthma, pneumonia, and lung cancer. v-TAC was validated on hemodynamically stable patients. Patients receiving treatments, for example non-invasive ventilation (NIV) or oxygen therapy, were also studied.

    The typical approach was to collect a reference sample (ABG1) and simultaneously measure the arterial oxygen saturation (SpO2) using a pulse oximeter and collect a peripheral venous sample. In clinical practice, it is not possible to do the steps simultaneously, so typically SpO2 is measured first, then the arterial sample is collected, and as soon as possible after that the venous (VBG) sample is collected. In practice, this means the VGB sample is often collected 1-5 minutes after the SpO2 measurement and in some cases after more time has elapsed.

    The repeatability of both arterial blood gas measurements and venous blood gas measurements is affected by pre-analytical errors in the time span from taking to analyzing the blood sample, and by analytical errors. Additionally, both arterial blood gas and venous blood gas are affected by biological fluctuations. When comparing two subsequent measurements, the biological change (e.g., hypo- or hyperventilation) has an impact on the result.

    Highlighted publications:

    • Shastri L et al. The use of venous blood gas in assessing arterial acid-base and oxygenation status - an analysis of aggregated data from multiple studies evaluating the venous to arterial conversion (v-TAC) method. Expert Rev Respir Med. 2024 July; 18(7):553-559.
    • Davies M et al. (2023). BMJ Open Respir Res 10:e001537. doi:10.1136/bmjresp-2022-001537
    • Shastri L et al. (2021). Mathematically arterialised venous blood is a stable representation of patient acid–base status at steady state following acute transient changes in ventilation. J Clin Monit Comput. doi:10.1007/s10877-021-00764-3.
    • Weber M, Cave G. (2021). Trending peripheral venous pCO2 in patients with respiratory failure using mathematically arterialised venous blood gas samples. BMJ Open Resp Res 8: e000896. doi:10.1136/ bmjresp-2021-000896.
    • Thomsen LP et al. (2021). Evaluation of Mathematical Arterialization of Venous Blood in Intensive Care and Pulmonary Ward Patients. Respir 100(2): 164-172. doi:10.1159/000512214.
    • Ekström M et al. (2019). Calculated arterial blood gas values from a venous sample and pulse oximetry: Clinical validation. PLoS ONE 14(4): e0215413. doi:10.1371/journal.pone.0215413.

    Additional publications:

    • Lumholdt M et al. (2019). Mathematical arterialisation of peripheral venous blood gas for obtainment of arterial blood gas values: a methodological validation study in the clinical setting. J Clin Monit Comput 33:733-740. doi:10.1007/s10877-018-0197-1.
    • Lumholdt M et al. (2018). Can routine blood gas screening identify patients with unsuspected acid-base conditions and lead to optimised triage group allocation? BMJ Open 8(Suppl 1):A1-A34. doi:10.1136/10.1136/bmjopen-2018-EMS.65. 
    • Kamperidis P et al. (2018). Optimising Acute Non-Invasive Ventilation Care in the NHS; the v-TAC approach. BMJ Thorax doi:10.1136/thorax-2018-212555.429.
    • Manuel A et al. (2017). A method for calculation of arterial blood gas values from measurements in the peripheral blood (v-TAC): The first UK study. Eur Resp J 50: PA4734. doi:10.1183/1393003.congress-2017.PA4734.
    • Kelly AM et al. (2013). Agreement between mathematically arterialised venous versus arterial blood gas values in patients undergoing non-invasive ventilation: a cohort study. Emerg Med J 31:e46-e49. doi:10.1136/emermed-2013-202879.
    • Rees SE et al. (2012). Calculating acid-base and oxygenation status during COPD exacerbation using mathematically arterialised venous blood. Clin Chem Lab Med 50(12):2149-2154. doi:10.1515/cclm-2012-0233.
    • Tygesen G et al. (2012). Mathematical arterialization of venous blood in emergency medicine patients. Eur J Emerg Med 19:363-372. doi:10.1097/MEJ.0b013e32834de4c6.
    • Oddershede L et al. (2011). The cost-effectiveness of venous-converted acid-base and blood gas status in pulmonary medical departments. ClinicoEconomics Outcomes Res (3):1-7. doi:10.2147/CEOR.S14489.
    • Rees SE et al. (2009). Converting venous acid-base and oxygen status to arterial in patients with lung disease. Eur Respir J (26):1141-1147. doi:10.1183/09031936.00140408.
    • Toftegaard M et al. (2009). Evaluation of a method for converting venous values of acid-base and oxygenation status to arterial values. Emerg Med J (26): 268-272. doi:10.1136/emj.2007.052571.

    The v-TAC Standalone software application is a server-based application that works seamlessly with existing blood gas analyzers from leading manufacturers.

    The v-TAC Standalone software is not installed on the blood gas analyzer itself. Instead, the v-TAC software is a standalone software application designed to run on a small footprint Windows virtual server or a dedicated computer in the hospital’s IT environment.

    A single instance of the v-TAC Standalone software can service all blood gas analyzers in the hospital.

    During normal operation, v-TAC Standalone software operates seamlessly as a background process and does not require any attention or application management

    In pilots and clinical studies using measured arterial blood gas as the reference, take note of the following recommendations and precautions:

    • Collect arterial and venous blood samples simultaneously
    • Ensure high quality in sample collection
    • Exclude samples with signs of pre-analytical errors
    • Ensure patient ventilatory stability before and during sample collection
    • Use proper statistical methods to evaluate the results.
    • If the data is entered manually, verify the data carefully for correctness before analysis

    General notes about pulse oximetry:10

    The use of pulse oximetry to estimate the arterial saturation level has a certain patient-to-patient variability. To receive ISO 80601-2-61 certification, pulse oximeters must have a performance of ±4%, but in clinical practice, it may be as much as 10%.

    Underestimation of SpO2 is not uncommon, e.g., if the pulse oximeter picks up a poor signal due to poor peripheral perfusion, incorrect positioning of the probe, or similar. 

    Summary about v-TAC sensitivity to inaccurately measured SpO2:10

    For pH and pCO2, simulations indicate that SpO2 changes of ±10% will cause pH to change in a range of 0.02 pH units and pCO2 to change in a range of 3.5 mmHg. v-TAC will, to a high degree, correct for the arterial-to-venous difference caused by aerobic metabolism.

    For pO2, the accuracy of the calculated pO2 depends on the accuracy of the SpO2 measurement and the specific SpO2 value, where pO2 is less sensitive to inaccurate SpO2 values from approximately 95% and below and more sensitive to inaccurate SpO2 values from approximately 96% and above.

    To evaluate whether the v-TAC performance is acceptable to be a potential substitute for arterial blood gas testing in certain patient groups, it is important to understand the comparability of two repeated arterial blood gas tests. We found three studies that investigated this question.11-13

    Common for all three studies by Mallat, Toftegaard, and Daher is that the data were collected from patients with an indwelling arterial catheter, removing the risk of collecting arterial blood with a mix of venous blood.

    Conclusion: The v-TAC performance studies show that the performance of v-TAC versus a reference arterial blood gas test is comparable to the repeatability of consecutive arterial blood gas tests.

    A study by Shastri et al. from 2021 shows how arterial acid-base values change more rapidly than venous acid-base values with fluctuating breathing patterns.1

    The conclusion was: “This study reaffirms the reliability of the physiology-based mathematical model for transformation of venous blood acid–base status to arterialised equivalents. In addition, it also shows that arterialised venous blood is a more stable representative of steady state arterial blood gas values following acute, transient changes in ventilation”.

    • Shastri L et al. (2021). Is venous blood a more reliable description of acid-base state following simulated hypo- and hyperventilation? Scand J Trauma Resusc 29: 35. doi: 10.1186/s13049-021-00848-8
    • Thomsen LP et al. (2020). Arterial and transcutaneous variability and agreement between multiple successive measurements of carbon dioxide in patients with chronic obstructive lung disease. Respir Physiol Neurobiol 280: 103486. doi: 10.1016/j.resp.2020.10348
    • Schütz N et al. (2019) Can venous blood gas be used as an alternative to arterial blood gas in intubated patients at admission to the emergency department? A retrospective study. Open Access Emerg 11: 305–312. doi:10.2147/OAEM.S228420
    • McKeever TM et al. (2016). Using venous blood gas analysis in the assessment of COPD exacerbations: a prospective cohort study. Thorax 71: 210–215. doi:10.1136/thoraxjnl-2015-207573
    • Mallat J et al. (2015). Repeatability of Blood Gas Parameters, pCO2 Gap, and pCO2 Gap to Arterial-to-Venous Oxygen Content Difference in Critically Ill Adult Patients. Medicine 94(3): e415. doi:10.1097/MD.0000000000000415
    • Byrne AL et al. (2014). Peripheral venous and arterial blood gas analysis in adults: are they comparable? A systematic review and meta-analysis. Respirology 19: 168–175. doi:10.1111/resp.12225
    • Kelly AM. (2013). Agreement between arterial and venous blood gases in emergency medical care: a systematic review. Hong Kong J Emerg Med 21: 166-171. doi: 10.1177/102490791302000307

    Related products

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      Prof Rees from the R-Care Department of Health Sciences and Technology in Aalborg University talks about v-TAC software

      Watch the ASPIRE webinar: Using physiology-based mathematical models to calculate arterial blood gas values from venous blood

      Professor Rees from the Respiratory and Critical Care group (R-Care) Department of Health Sciences and Technology in Aalborg University, Denmark, explains the limitations of venous blood gas testing and introduces v-TAC—an alternative to get Arterial Blood Gas estimates without the need of performing arterial punctures in patients.

      Contact us

      Do you have questions about our products or services? We’re here to help. Contact a Roche representative in your region.

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      *Before using v-TAC please consult the v-TAC Standalone 1.5 User Guide for complete information.

      References:

      1. Shastri L et al. (2024). Expert Rev Respir Med 18(7):553-559. doi: 10.1080/17476348.2024.2378021.
      2. Ekström M et al. (2019). PLoS ONE 14(4): e0215413. doi:10.1371/journal.pone.0215413
      3. Kamperidis P et al. (2018). BMJ Thorax 73:A250. doi:10.1136/thorax-2018-212555.429
      4. Rees SE et al. (2012). Clin Chem Lab Med 50(12): 2149-2154. doi:10.1515/cclm-2012-0233
      5. Low LL et al. (1995). Chest 108: 216-219. doi:10.1378/chest.108.1.216
      6. Perme C et al. (2013). Cardiopulm Phys Ther J 24(2): 12-17. doi:10.1097/01823246-201324020-00003
      7. Davies M et al. (2023). BMJ Open Respir Res 10:e001537. doi:10.1136/bmjresp-2022-001537
      8. Weber M, Cave G. (2021). BMJ Open Resp Res 8: e000896. doi:10.1136/ bmjresp-2021-000896
      9. Schütz N et al.(2019) Open Access Emerg 11: 305–312. doi:10.2147/OAEM.S228420
      10. F. Hoffmann-La Roche Ltd. v-TAC Standalone software version 1.5 User Guide
      11. Toftegaard M et al. (2009). Emerg Med J 26: 268-272. doi:10.1136/emj.2007.052571
      12. Mallat J et al. (2015). Medicine 94(3): e415 doi:10.1097/MD.0000000000000415
      13. Daher A et al. (2022). Respiration. doi:10.1159/000524491