The Journal of ExtraCorporeal Technology No 58-1 | Seite 51

M.-H. Lee and T. Rosenthal: J Extra Corpor Technol 2026, 58, 43 – 50 45

Table 1. Average error in mmHg and % Error of the calculated in-line PaO 2.

Avg: average; SD: standard deviation.

Table 2. Error distribution of the calculated in-line PaO 2 and the correlation coefficient( R) between the error in mmHg and patient weight.

% Pt: percentage of patients, see Table 1 to find total patient numbers for each blood gas series; $: R value of the linear correlation analysis between the error in mmHg and patient weight.

After the initiation of rewarming, the 4th blood gas series from 78 patients and the 5th blood gas series from 51 were collected( Table 1). Data from the Quantum System and anesthesia records corresponding to each blood gas series were manually extracted.

Error in mmHg and % Error

Errors in mmHg and % Error for PaO 2 and PaCO 2 during the cooling and cooled periods( the 1st to 3rd blood gas series) were calculated using pH-stat values, while those during the rewarming and rewarmed periods( the 4th and 5th blood gas series) were calculated using alpha-stat values. The formulas are:

Error in mmHg ¼ Quantum System value � iSTAT value ðmmHgÞ % Error ¼ ½ ðQuantum System value � iSTAT valueÞ = iSTAT valueŠ100 ð%

Þ:

Data analysis Microsoft Excel Office 365 was employed for data input, calculations, scatter plots, fitted linear regression analysis, Bland-Altman analysis, and other statistical analyses, including correlation coefficient( R), bias, and limits of agreement( LOA) [ 18 – 20 ].

Result

Calculated in-line PaO 2 is significantly overestimated before the first in vivo calibration

Asignificant error in the calculated in-line PaO 2 of the Quantum System with the FX05 oxygenator was observed at the 1st blood gas series on CPB. The calculated in-line PaO 2 is almost always overestimated compared to the measured

PaO 2 on iSTAT with an average % Error of 48.3 ± 41.3 %( Table 1), which exceeds the acceptable target of ± 15 % [ 12, 13 ]. These large errors and standard deviation( SD) indicate that the accuracy and precision of the calculated in-line PaO 2 are unacceptable before the first in vivo calibration.

After the first in vivo calibration, at the 2nd blood gas series, the average error improved significantly to �7.7 %, though SD remained high at ± 27.8 %. By the third blood gas series, the accuracy and precision further improved, with an average error of 3.4 ± 10 % after the second in vivo calibration( Table 1).

As shown in the % Error, the calculated in-line PaO 2 is significantly overestimated at the 1st blood gas series. The average error in mmHg was 117 mmHg, and the standard deviation was ± 64.5 mmHg( Table 1). Over-estimation occurred in 99 % of the patients, and 53 % had over-estimation higher than 100 mmHg( Table 2). After the first and second in vivo calibrations, the over-estimation of the calculated in-line PaO 2 was corrected as 4.4 % and 0 % of the patients had over-estimation higher than 100 mmHg at the 2nd and 3rd blood gas series, respectively( Table 2). The error of the calculated in-line PaO 2 at the 1st blood gas series strongly correlates with patient weight

As patient weight increases, oxygen consumption likely increases, which may contribute to the error if the calculated in-line PaO 2 does not reflect the oxygen consumption correctly. Therefore, we examined whether the error in mmHg has a correlation with patient weight. As shown in Figure 1A, we found a strong linear correlation( R = 0.62, slope = 13, Y intercept = 40) between the error in mmHg at the 1st blood gas series and patient weight. The error in mmHg increases as patient weight increases. However, after the first in vivo calibration,