Comparison of mathematically arterialised venous blood gas sampling with arterial, capillary, and venous sampling in adult patients with hypercapnic respiratory failure: a single-centre longitudinal cohort study

Michael Gordon Davies; Dariusz Rafal Wozniak; Timothy George Quinnell; Earl Palas; Susan George; Yingchang Huang; Ruwanthi Jayasekara; Victoria Stoneman; Ian Edward Smith; Lars Pilegaard Thomsen; Stephen Edward Rees

doi:10.1136/bmjresp-2022-001537

Comparison of mathematically arterialised venous blood gas sampling with arterial, capillary, and venous sampling in adult patients with hypercapnic respiratory failure: a single-centre longitudinal cohort study

BMJ Open Respir Res. 2023 Jun;10(1):e001537. doi: 10.1136/bmjresp-2022-001537.

Affiliations

¹ Respiratory Support and Sleep Centre, Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK Michael.davies10@nhs.net.
² Respiratory Support and Sleep Centre, Royal Papworth Hospital NHS Foundation Trust, Cambridge, UK.
³ Respiratory and Critical Care group, Aalborg University, Aalborg, Denmark.

Abstract

Background: Accurate arterial blood gas (ABG) analysis is essential in the management of patients with hypercapnic respiratory failure, but repeated sampling requires technical expertise and is painful. Missed sampling is common and has a negative impact on patient care. A newer venous to arterial conversion method (v-TAC, Roche) uses mathematical models of acid-base chemistry, a venous blood gas sample and peripheral blood oxygen saturation to calculate arterial acid-base status. It has the potential to replace routine ABG sampling for selected patient cohorts. The aim of this study was to compare v-TAC with ABG, capillary and venous sampling in a patient cohort referred to start non-invasive ventilation (NIV).

Methods: Recruited patients underwent near simultaneous ABG, capillary blood gas (CBG) and venous blood gas (VBG) sampling at day 0, and up to two further occasions (day 1 NIV and discharge). The primary outcome was the reliability of v-TAC sampling compared with ABG, via Bland-Altman analysis, to identify respiratory failure (via PaCO₂) and to detect changes in PaCO₂ in response to NIV. Secondary outcomes included agreements with pH, sampling success rates and pain.

Results: The agreement between ABG and v-TAC/venous PaCO₂ was assessed for 119 matched sampling episodes and 105 between ABG and CBG. Close agreement was shown for v-TAC (mean difference (SD) 0.01 (0.5) kPa), but not for CBG (-0.75 (0.69) kPa) or VBG (+1.00 (0.90) kPa). Longitudinal data for 32 patients started on NIV showed the closest agreement for ABG and v-TAC (R²=0.61). v-TAC sampling had the highest first-time success rate (88%) and was less painful than arterial (p<0.0001).

Conclusion: Mathematical arterialisation of venous samples was easier to obtain and less painful than ABG sampling. Results showed close agreement for PaCO2 and pH and tracked well longitudinally such that the v-TAC method could replace routine ABG testing to recognise and monitor patients with hypercapnic respiratory failure.

Trial registration number: NCT04072848; www.

Clinicaltrials: gov.

Keywords: Assisted Ventilation; Non invasive ventilation; Respiratory Measurement.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Adult
Carbon Dioxide*
Cohort Studies
Humans
Longitudinal Studies
Reproducibility of Results
Respiratory Insufficiency* / diagnosis
Respiratory Insufficiency* / etiology
Respiratory Insufficiency* / therapy

Substances

Carbon Dioxide

Associated data

ClinicalTrials.gov/NCT04072848