J Extra Corpor Technol 2026, 58, 43 – 50 Ó The Author( s), published by EDP Sciences, 2026 https:// doi. org / 10.1051 / ject / 2025051
Available online at: ject. edpsciences. org
ORIGINAL ARTICLE
Is continuous in-line blood gas monitoring reliable during cardiopulmonary bypass when PaO 2 and PaCO 2 are calculated rather than measured?
Min-Ho Lee( PhD, CCP) * and Tami Rosenthal( MBA, CCP)
Perfusion Services, Children’ s Hospital of Philadelphia, 3401 Civic Center Blvd., Philadelphia, PA 19104, USA Received 14 May 2025, Accepted 2 September 2025
Abstract – Background: The accuracy and precision of continuous in-line blood gas monitoring( CILBGM) are crucial for optimal blood gas management during cardiopulmonary bypass( CPB) and improved patient outcomes. CILBGM devices, such as the CDI 500 / 550 system, measure PaO 2 and PaCO 2, and B-Capta measures PaO 2 through direct contact with arterial blood. However, the Quantum perfusion system with Quantum Ventilation 2( Quantum System) does not measure but calculates PaO 2 and PaCO 2 using several non-invasive sensors and proprietary formulas. We have observed that the calculated in-line PaO 2 and PaCO 2 values from Quantum System are frequently significantly higher than those obtained from iSTAT, a point-of-care blood analyzer, exceeding acceptable targets. Methods: We conducted a retrospective study involving 81 patients who underwent cardiac surgery using the Quantum System with its own CILBGM and the FX05 oxygenator. The aim was to identify the degree, timing, and possible patterns of error of the calculated in-line PaO 2 and PaCO 2. Results: Our study showed that the errors of calculated in-line PaO 2 exceed the acceptable target at the 1st blood gas series and during the rewarming and rewarmed periods, correlating with patient weight. The calculated in-line PaCO 2 exhibited an upward drift during the rewarming period, correlating with the temperature gradient rather than patient weight. Based on several correlations identified, we derived a formula to predict FiO 2 based on patient weight, which would achieve the target PaO 2 at the 1st blood gas series when using the FX05 oxygenator. Conclusion: We identified when and how the errors in calculating in-line PaO 2 and PaCO 2 occurred and developed several recommendations to minimize significant deviations from actual PaO 2 and PaCO 2 during CPB. Our results suggest that achieving acceptable PaO 2 and PaCO 2 calculations throughout CPB using a single universal formula for each, embedded in the Quantum System, is challenging due to the variety of oxygenators available, different patient sizes, and changing conditions during CPB.
Key words: Continuous in-line blood gas monitoring, PaO 2 and PaCO 2, Measured vs. calculated, Laboratory blood analyzer, Cardiopulmonary bypass.
Introduction
During cardiopulmonary bypass( CPB), accurate and precise blood gas and electrolyte values are crucial for better patient care and outcomes. Laboratory blood analyzers, which employ an electrochemical method and are considered the gold standard, can provide blood gas analysis by sampling the blood intermittently and on demand. In contrast, continuous in-line blood gas monitoring( CILBGM) devices, which employ optical fluorescence and spectrophotometric methods and are considered trending devices, can continuously measure and display results [ 1 – 4 ].
CILBGM can provide real-time monitoring of patient acidbase and oxygenation status, which has been shown to be a valuable tool for more accurate blood gas management and
* Corresponding author: mnhlee08 @ gmail. com improved patient outcomes [ 2, 3, 5 – 8 ]. The usage of CILBGM devices during CPB has increased over the years and is recommended as a standard of care [ 1, 9 – 11 ]. Since CILBGM devices employ a different method from laboratory blood analyzers, their accuracy and precision must meet acceptable targets when compared to laboratory blood analyzers. Clinical Laboratory Improvement Amendments( CLIA) guidelines provided new accuracy standards in 2025 for clinical laboratory testing. According to the CLIA guidelines, PO 2 should be within ± 15 mmHg or ± 15 %( greater), and PCO 2 should be within ± 5 mmHg or ± 8 %( greater) [ 12, 13 ].
CILGBM devices, such as the CDI system 500 / 550( Terumo Medical Corporation, Somerset, NJ), measure PaO 2 and PaCO 2, and B-Capta( Liva Nova, London, UK) measures PaO 2 through direct contact with arterial blood using the optical fluorescence method. Several studies showed that PaO 2 and PaCO 2 of the CDI system 500 were acceptable( within the
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