Oxygen saturation in intraosseous sternal blood measured by CO-oximetry and evaluated non-invasively during hypovolaemia and hypoxia – a porcine experimental study

Purpose: This study intended to determine, and non-invasively evaluate, sternal intraosseous oxygen saturation (SsO 2 ) and study its variation during provoked hypoxia or hypovolaemia. Furthermore, the relation between SsO 2 and arterial (SaO 2 ) or mixed venous oxygen saturation (SvO 2 ) was investigated. Methods: Sixteen anaesthetised male pigs underwent exsanguination to a mean arterial pressure of 50 mmHg. After resuscitation and stabilisation, hypoxia was induced with hypoxic gas mixtures (air/N 2 ). Repeated blood samples from sternal intraosseous cannulation were compared to arterial and pulmonary artery blood samples. Reflection spectrophotometry measurements by a non-invasive sternal probe were performed continuously. Results: At baseline SaO 2 was 97.0% (IQR 0.2), SsO 2 73.2% (IQR 19.6) and SvO 2 52.3% (IQR 12.4). During hypovolaemia, SsO 2 and SvO 2 decreased to 58.9% (IQR 16.9) and 38.1% (IQR 12.5), respectively, p