Reliability and validity of non-invasive determined haemoglobin mass and blood volumes

Introduction. The carbon monoxide (CO) re-breathing method used for the determination of haemoglobin mass (Hbmass) is associated with blood sample analysis (in this study: Radiometer ABL800). As an alternative hereto the aim of the present study was to evaluate the use of a portable and non-invasive CO pulse-oximeter (Rad-57). Method. With simultaneous determination of CO in the circulation by ABL800 (%HbCO) and Rad-57 (SpCO) Hbmass and blood volume (BV) were determined in duplicates in 24 volunteers. Percentage of typical errors (%TE) within methods and linear correlations between the two procedures were computed. Results. Hbmass (Rad-57 = 798  230 g; ABL800 = 781  192 g) and BV (Rad-57 = 5700  1373 ml; ABL800 = 5581  1096 ml) were similar between methods. However, the %TE for Hbmass was higher (p < 0.001) for Rad-57 (5.84  5.29 %) than for ABL800 (1.35  1.13 %). Similarly, the %TE for BV was higher (p < 0.001) for Rad-57 (6.06  5.76 %) than for ABL800 (1.48  1.25 %). Lower (p < 0.05) correlation coefficients between the methods were found when Hbmass > 905 g and BV > 6193 ml. Conclusion. Assessment of SpCO by Rad-57 resulted in considerably less precise determinations of Hbmass and BV, especially for high values. Thus, non-invasive assessment of Hbmass and BV cannot be recommended for scientific purposes, but may nonetheless be useful in clinical settings.