Introduction Accurate assessment of gas exchange is essential for the management of hypercapnic respiratory failure. The 2017 NCEPOD and 2018 BTS reports on Non-Invasive-Ventilation (NIV) revealed quality issues across the NHS on the delivery of NIV. Here we present the validation of an alternative to ABG, v-TAC (venous-To-Arterial-Conversion), which provides ‘arterialised’ samples from venous blood gases (VBG) and could revolutionise NIV management.

Methodology Twenty patients with respiratory compromise were randomly selected from the Respiratory, or Critical Care Units. ABG and VBG samples were obtained and analysed within fifteen minutes. Oxygen saturation (SpO₂) was measured via standard pulse oximetry. VBG and SpO₂ were then blindly converted to ‘arterialised’ gas via v-TAC and compared to ABG with the technical support of OBI Medical. Arterial and v-TAC pH, pCO₂ and pO₂ were plotted using Bland-Altman Plots. Rules were applied to venous/arterial sample pairs to identify non-physiological appearing sets. Subsets of peripheral (pVBG) samples were analysed separately from central VBG ones (cVBG).

Discussion In accordance to similar studies, pVBG samples arterialised via v-TAC were comparable to ABG samples in terms of pH, pCO₂ and pO₂, showing 95% limits of agreement within clinically acceptable limits. v-TAC always provided a converted sample with physiological-looking values. However, if our applied rules deemed the original VBG/ABG pair a poor match, its further analysis provided plausible explanations for the apparent disparity between VBG and ABG, and hence between v-TAC and VBG/ABG. The small subset of cVBG samples was plotted separately with comparable results.

Conclusion v-TAC is an advanced software algorithm that converts VBG to ABG values with great accuracy and has great potential benefits in NIV management. We envisage the implementation of a nurse-led pathway which will enable nurse autonomy in setting up and managing NIV, thus enhancing compliance in monitoring treatment progress and ensuring timely intervention. Ultimately, the goal is to improve compliance to standards of care leading to improved quality of care and outcomes, and reduced length of stay, costs and mortality.

Reference

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