Non-invasive capnodynamic mixed venous oxygen saturation during major changes in oxygen delivery

Abstract

Mixed venous oxygen saturation (SvO2) is an important variable in anesthesia and intensive care but currently requires pulmonary artery catheterization. Recently, non-invasive determination of SvO2 (Capno-SvO2) using capnodynamics has shown good agreement against CO-oximetry in an animal model of modest hemodynamic changes. The purpose of the current study was to validate Capno-SvO2 against CO-oximetry during major alterations in oxygen delivery. Furthermore, evaluating fiberoptic SvO2 for its response to the same challenges. Eleven mechanically ventilated pigs were exposed to oxygen delivery changes: increased inhaled oxygen concentration, hemorrhage, crystalloid and blood transfusion, preload reduction and dobutamine infusion. Capno-SvO2 and fiberoptic SvO2 recordings were made in parallel with CO-oximetry. Respiratory quotient, needed for capnodynamic SvO2, was measured by analysis of mixed expired gases. Agreement of absolute values between CO-oximetry and Capno-SvO2 and fiberoptic SvO2 respectively, was assessed using Bland–Altman plots. Ability of Capno- SvO2 and fiberoptic SvO2 to detect change compared to CO-oximetry was assessed using concordance analysis. The interventions caused significant hemodynamic variations. Bias between Capno-SvO2 and CO-oximetry was + 3% points (95% limits of agreements – 7 to + 13). Bias between fiberoptic SvO2 and CO-oximetry was + 1% point, (95% limits of agreements − 7 to + 9). Concordance rate for Capno-SvO2 and fiberoptic SvO2 vs. CO-oximetry was 98% and 93%, respectively. Capno-SvO2 generates absolute values close to CO-oximetry. The performance of Capno-SvO2 vs. CO-oximetry was comparable to the performance of fiberoptic SvO2 vs. CO-oximetry. Capno-SvO2 appears to be a promising tool for non-invasive SvO2 monitoring.

Standardized blood volume changes monitored by capnodynamic hemodynamic variables: An experimental comparative study in pigs

“…The animals were handled in accordance with the animal experimentation guidelines of the Uppsala Animal Ethics Committee and the study was approved by Uppsala Animal Ethics Committee in August 2016 (Uppsala, Sweden case number C75/16). The subjects used in the current study have previously been part of another investigation, assessing the performance of Capno‐SvO 2 against CO‐oximetry 15 …”

Capnodynamics—Measuring cardiac output via ventilation

“…A time plot of the experimental protocol showing simultaneous changes in mixed venous oxygen saturation for Capno‐SvO 2 and blood gas‐based CO‐oximetry measurements is shown in Figure 4. An additional experimental study in pigs has recently been published where the methods reliability in detecting major hemodynamic changes (induced by alternating levels of inhaled oxygen fraction, hemorrhage, blood transfusion, and crystalloid administration as well as infusion of inotropic substances) have been investigated 19 . In that study, Capno‐SvO 2 showed overall comparable performance with the reference methods CO‐oximetry and fiberoptic mixed venous oxygen saturation monitoring.…”

Capnodynamics – noninvasive cardiac output and mixed venous oxygen saturation monitoring in children

“…More importantly, the trending ability was 100% for Capno-SvO 2 compared to gold standard. To further challenge the method, an additional pediatric piglet model of major hemodynamic changes was used, using CO-oximetry and fiber optic SvO 2 as references (38). 11 piglets were exposed to a series of variations in inspiratory oxygen fraction, hemorrhage, crystalloid and blood transfusion, inferior cava vein occlusion and dobutamine infusion.…”