352 Critical Care Fellowship Program Directors’ Opinions of Emergency Medicine Applicants

Abstract

Study Objectives: Central venous oxygen saturation (ScVO2) is commonly used in clinical practice as a surrogate for cardiac output and delivery of oxygen to tissues. However, ScVO2 is invasive, as it requires central vein cannulation. A noninvasive alternative, such as End-Tidal Oxygen (ETO2), would be beneficial to patients, as it is painless, and without the risks of central vein cannulation. If a strong level of agreement exits and a correlation is present, ETO2 could be used as a non-invasive measure to determine the heart's ability to circulate blood and oxygen to tissues.The objective of this study is to determine in patients requiring hemodynamic support (ie, pressor support or large volume resuscitation) how well ETO2 compares to ScVO2 as a surrogate for cardiac output. We also sought to determine the correlation between the two.Methods: This is a prospective observational study of patients in the emergency department in which ETO2 was measured non-invasively at the time of ScVO2 collection from a central line. Approximately 2ml of blood was drawn from a central venous catheter by a nurse at the same time ETO2 measurements were recorded. Blood samples were analyzed immediately by a validated point-of-care blood gas analyzer. ScVO2 and ETO2 measurements were recorded, along with data including vitals signs, lab values, and the patient's diagnosis.Statistical Analysis: Bland-Altman Plot for level of agreement and bias was generated and Pearson correlation was calculated to describe relationship between ScVO2 and EtO2 as well as their ability to measure cardiac output. Demographic data is presented with descriptive statistics.Results: Twenty-seven patients have been enrolled to date. The average lactate for the group was 2.5 (95% CI 1.5 to 3.5) with an average hock index of 0.85 indicating the presence of a hypoperfused state. Pearson correlation was modest (0.63). The mean ScVO2 was 73 (95% CI 68 to 78) and ETO2 was 52 (95% CI 42 to 62). The Bland-Altman Plot demonstrates moderate level of agreement with bias towards ETO2 under measuring compared to ScVO2 (See Graph).Conclusion: We found a modest agreement between EtO2 and ScVO2 with some bias to under measuring for ETO2. ETO2 may offer some benefit in helping clinicians to determine the presence of hypoperfusion.