Sintupech P.Anantho A.Songnok K.Kitsommart R.Mahidol University2026-05-312026-05-312026-06-01European Journal of Pediatrics Vol.185 No.6 (2026)03406199https://repository.li.mahidol.ac.th/handle/123456789/117000Abstract: This study aims to compare CrSO<inf>2</inf> measured simultaneously by Masimo O3 and INVOS during the first 15 min after birth in healthy term infants and to evaluate agreement and derived cerebral fractional tissue oxygen extraction (cFTOE). In this prospective observational study, 65 healthy term infants were monitored immediately after birth using Masimo O3 and INVOS 7100 applied simultaneously with randomized hemispheric placement. Pre-ductal oxygen saturation (SpO<inf>2</inf>) was recorded continuously. Minute-specific values were derived from aggregated measurements during the final 30 s of each minute. Paired comparisons were performed using Wilcoxon signed-rank test. Agreement was assessed using Bland–Altman analysis with regression evaluation for proportional bias. Both devices demonstrated a similar temporal increase in CrSO<inf>2</inf> during the first 5 min, with relative stabilization thereafter. From minute 4 onward, Masimo O3 values were lower than INVOS, with significant differences at minutes 5 to 11 and min 14 (p < 0.05). Overall mean bias was − 2.8%, with 95% limits of agreement from + 18.0 to − 23.6%. Significant proportional bias was present (R² = 0.11, p < 0.001). When CrSO<inf>2</inf> was < 60%, mean bias was + 28.7% with wide limits of agreement. Masimo O3 derived cFTOE values were consistently higher at several time points. No significant hemispheric differences were detected. Conclusion: Masimo O3 and INVOS show similar temporal patterns but an oxygenation-dependent proportional bias. CrSO<inf>2</inf> values are device-specific and not interchangeable, particularly at lower saturation levels during early transition. (Table presented.)MedicineArticleSCOPUS10.1007/s00431-026-07017-y2-s2.0-1050397269861432107642159790