Abstract

Background
Acute hypercapnic respiratory failure (AHRF) requires immediate ventilatory support and precise carbon dioxide monitoring. Arterial blood gas (ABG) analysis is the gold standard for the quantitation of PaCO2, but it is intermittent, invasive, and occasionally painful. Transcutaneous carbon dioxide (TcCO2) monitoring offers the advantage of continuous noninvasive monitoring but its usefulness in acute noninvasive ventilation (NIV) is doubtful.

Objective
To establish the diagnostic accuracy, agreement, and clinical usefulness between TcCO2 and ABG-derived PaCO2 in adult patients receiving NIV for AHRF.

Methods
Systematic review with meta-analysis using PRISMA-DTA was performed. MEDLINE, Embase, and CENTRAL databases were searched up to June 2025. Studies potentially eligible for inclusion compared TcCO2 with PaCO2 during acute NIV in adults. Two reviewers appraised quality using QUADAS-2 independently after preliminary screening, and data on correlation, agreement, tolerability, and clinical effect were extracted.

Results
Seven studies with over 400 patients combined. Correlations between TcCO2 and PaCO2 across the studies ranged between 0.85 and 0.97, with an overall estimate close to r = 0.91. In the Bland-Altman plots, satisfactory bias with limits of agreement was revealed. TcCO2 monitoring was tolerated without issue in the patients, reduced repetitive sampling with ABGs, and informed clinical decisions. No adverse effects were reported.

Conclusion
TcCO2 monitoring has excellent agreement with PaCO2 and is a safe, practical addition to ABG in acute NIV for AHRF. It provides real-time monitoring, better patient comfort, and potential increased efficiency. Larger trials will determine its effect on outcomes and its cost-effectiveness.