FETAL PULSE OXIMETRY - INFLUENCE OF TISSUE BLOOD CONTENT AND HEMOGLOBIN CONCENTRATION IN A NEW IN-VITRO MODEL

Objective: To assess the influence of the blood content of the tissue and the hemoglobin content of the blood upon pulse oximetry at oxygen saturation ranges that commonly occur in the fetus during birth. Metho d: A new in-vitro model, which differs conceptually from models used b y other authors, was developed to simulate the tissue. Our sensor meas ured absorption changes in red (640 nm) and infrared (880 nm) light as the blood concentration in the optical chamber changed in analogy to arterial pulsations. Results: Blood content of the tissue and hemoglob in content of the blood both affect the pulse oximetric measurement ad versely, especially at low oxygen saturations. Our simulations indicat e, for example, that at a true oxygen saturation (Sao(2)) of 30%, a bl ood content change from 10 to 6 vol% would cause an underestimation of Sao, by more than 16% points. Conclusion: Pulse oximetry at low satur ations should take the blood content of the tissue and hemoglobin cont ent of the blood into account in order to provide more accurate result s. (C) 1997 Elsevier Science Ireland Ltd.