Rapid and accurate measurement of carboxyhemoglobin (COHb) is essential in managing acute carbon monoxide poisoning (ACOP). Non-invasive pulse CO-oximetry (SpCO) offers a convenient alternative to arterial blood gas analysis (ABGA), but its clinical accuracy and reliability in low COHb severity remain uncertain. This study evaluated the agreement and predictive performance of SpCO compared to arterial COHb in ACOP patients. In this prospective observational study, 81 ACOP patients underwent paired measurements of SpCO and arterial COHb. Patients were categorized into three groups based on COHb severity: low ( 20%). Agreement was assessed using Deming and Passing–Bablok regression, Lin’s concordance correlation coefficient (CCC), Bland–Altman analysis, and accuracy metrics (R2, RMSE, MAE). A linear mixed-effects model (LMEM) was constructed to identify predictors of COHb, incorporating SpCO, treatment status, and oxygenation parameters. At baseline, SpCO showed only limited agreement with arterial COHb, with moderate concordance in the moderate COHb range but substantial positive bias and wide limits of agreement, particularly at higher concentrations. After HBOT, agreement deteriorated markedly, with unstable regression slopes, reduced concordance, and persistent heteroscedasticity across all severity strata. Similar deterioration was observed at follow-up in the non-HBOT group. In mixed-effects modeling, SpCO, COHb severity, and treatment time point were significant predictors of arterial COHb, whereas age, sex, and oxygenation parameters were not. The model demonstrated strong explanatory performance (marginal R2 = 0.904; RMSE = 2.61). Agreement between non‑invasive SpCO and arterial COHb is highly dependent on COHb concentration and measurement timing and declines markedly after HBOT, limiting the interchangeability of these methods in post‑treatment settings. SpCO may provide adjunctive information at baseline, particularly in moderate COHb ranges, but does not achieve sufficient agreement or precision to replace arterial COHb measurement, especially after treatment. Arterial COHb remains essential for accurate post-treatment assessment in ACOP.
Lee et al. (Tue,) studied this question.