Detection of blood volume deficits through conjunctival oxygen tension monitoring

Abstract

Because acute blood loss may produce abnormal tissue perfusion and oxygenation before affecting blood pressure, we measured conjunctival (P_cjO2) and arterial (PaO₂) oxygen tensions and blood volume in 16 normotensive emergency department patients whose histories were consistent with significant blood loss. All eight patients with measured blood volume less than 85% of normal, as well as two euvolemic patients, had a P_cjO2/Pao₂ value of 0.57 or less, yielding a sensitivity of 100%, specificity of 75%, and positive predictive value of 80%. Lowering the cutoff point to 0.50 increased specificity and positive predictive value to 100% while reducing sensitivity to 88%. These results demonstrate that the P_cjo₂/Pao₂ ratio is an early, sensitive, and specific indicator of significant blood volume deficit.