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

Hemodynamic monitoring in children is challenging for many reasons. Technical limitations in combination with insufficient validation against reference methods, makes reliable monitoring systems difficult to establish. Since recent studies have highlighted perioperative cardiovascular stability as an important factor for patient outcome in pediatrics, the need for accurate hemodynamic monitoring methods in children is obvious. The development of mathematical processing of fast response mainstream capnography signals, has allowed for the development of capnodynamic hemodynamic monitoring. By inducing small changes in ventilation in intubated and mechanically ventilated patients, fluctuations in alveolar carbon dioxide are created. The subsequent changes in carbon dioxide elimination can be used to calculate the blood flow participating in gas exchange, i.e., effective pulmonary blood flow which equals the non-shunted pulmonary blood flow. Cardiac output can then be estimated and continuously monitored in a breath-by-breath fashion without the need for additional equipment, training, or calibration. In addition, the method allows for mixed venous oxygen saturation (SvO2) monitoring, without pulmonary artery catheterization. The current review will discuss the capnodyamic method and its application and limitation as well as future potential development and functions in pediatric patients.

Changed hemodynamics in acute vasoreactivity testing: prognostic predictors in chronic thromboembolic pulmonary hypertension.

Chronic thromboembolic pulmonary hypertension (CTEPH) is similar to pulmonary arterial hypertension (PAH) in its pathogenesis. Changed hemodynamic parameters in acute vasoreactivity testing (AVT) have proved to be prognostic predictors of PAH. We wanted to determine whether these changed indices also impacted the prognosis of CTEPH. Data was retrieved for 86 CTEPH patients who underwent right heart catheterization (RHC) with AVT at Shanghai Pulmonary Hospital from 2009 to 2018 and following up for 20 ± 15 months for event. Cox proportional hazards models were performed to determine the predictors of independent event-free survival. Receiver operating characteristic curve was plotted to determine the cut-off value of independent parameters in CTEPH. Kaplan-Meier method and log-rank test were used to perform the Survival analyses. Forty seven patients had an event. Many hemodynamic indices improved after AVT. The event-free group had better mean right atrial pressure, mean pulmonary arterial pressure, pulmonary vascular resistance (PVR) and oxygen saturation of mixed venous blood (SvO2) both at baseline and after AVT. The event-free group also showed higher cardiac output (CO) and cardiac index (CI) after AVT. Among the changed hemodynamic parameters during the AVT, ΔCO, ΔCO/baseline CO, ΔCI, ΔCI/baseline CI and ΔPVR/baseline PVR were significantly higher in the event-free group. Foremost, ΔPVR/baseline PVR, PVR after AVT and baseline SvO2 were independent predictors for event-free survival. Patients with SvO2 ≥ 61.65% at baseline or PVR < 8.09 WU after AVT or ΔPVR/baseline PVR ≥ 0.054 had significantly better survival. Hemodynamic indices both at baseline and after AVT as well as the changes in these indices reflected the severity of CTEPH. Baseline SvO2, PVR after AVT, and ΔPVR/baseline PVR could be used as independent predictors to estimate the outcomes of CTEPH patients.

Poor agreement in the calculation of venoarterial PCO2 to arteriovenous O2 content difference ratio using central and mixed venous blood samples in septic patients.

PURPOSE: Central venous minus arterial PCO2 to arterial minus central venous O2 content difference ratio (Pcv-aCO2/Ca-cvO2) has been proposed as a clinical surrogate for respiratory quotient. Our goal was to assess its interchangeability with mixed venous minus arterial PCO2 to arterial minus mixed venous O2 content difference ratio (Pmv-aCO2/Ca-mvO2). MATERIALS AND METHODS: This is a subanalysis of a previously published study. We studied 23 septic patients who had an indwelling Swan-Ganz catheter. The agreement between Pcv-aCO2/Ca-cvO2 and Pmv-aCO2/Ca-mvO2 was evaluated by Bland and Altman analysis. We also performed linear regression analysis with Pmv-aCO2/Ca-mvO2 as the dependent variable. RESULTS: 95% limits of agreement between Pcv-aCO2/Ca-cvO2 and Pmv-aCO2/Ca-mvO2 were 1.48. Pmv-aCO2/Ca-mvO2 was significantly correlated with hemoglobin and lactate (R2 = 0.48 and 0.31, respectively, P < 0.01 for both). CONCLUSIONS: In this study, Pcv-aCO2/Ca-cvO2 and Pmv-aCO2/Ca-mvO2 were not interchangeable. In addition, Pmv-aCO2/Ca-mvO2 is a composite variable, which depends on several determinants. Values of Pcv-aCO2/Ca-cvO2 should be cautiously interpreted in the assessment of critically ill patients.