Carboxyhemoglobinemia and Anemia are Associated with Unreliable Pulse Oximetry in the LVAD Population

Abstract

Purpose Although continuous pulse oximetry (SpO2) is applied ubiquitously to assess oxygenation in the LVAD population, its reliability has been unconfirmed. By case-control analysis, we sought to identify clinical scenarios where SpO2 was discrepant from the gold standard, arterial oxygen saturation (SaO2) measured by co-oximetry. Methods We retrospectively evaluated all patients who underwent implantation of a continuous flow LVAD at a single institution between July 2016 and July 2018. Simultaneous oxygen measurements for SaO2 by arterial blood gas co-oximetry and for SpO2 by transcutaneous pulse oximetry were collected. Case patients, defined as having simultaneous SpO2 and SaO2 difference > 3% at anytime after index surgery, were compared to controls ( Results A total of 123 subjects constituted our study cohort of whom 44 cases and 55 controls were identified. Table 1 presents baseline clinical measures. Utilizing a logistic regression model, we identified that elevated COHb has an increased risk (OR= 2.04 (95% CI: 1.02- 4.02; p=0.05), and that elevated Hgb has a protective effect (OR= 0.74 (95%CI: 0.56- 0.94; p= 0.02) on developing >3% difference between SaO2 and SpO2 measures. Conclusion In patients after index LVAD implantation, total hemoglobin and carboxyhemoglobin are associated with discrepancy between SaO2 and SpO2 and should be taken into consideration when evaluating hypoxemia.