Continuous monitoring of membrane lung carbon dioxide removal during ECMO: experimental testing of a new volumetric capnometer

Abstract

Background: Extracorporeal membrane oxygenation constitutes a complex support modality, and accurate monitoring is required. An ideal monitoring system should promptly detect ECMO malfunctions and provide real-time information to optimize the patient–machine interactions. We tested a new volumetric capnometer which enables continuous monitoring of membrane lung carbon dioxide removal (V′CO2ML), to help in estimating the oxygenator performance, in terms of CO2 removal and oxygenator dead space (VDsML). Methods: This study was conducted on nine pigs undergoing veno-arterial ECMO due to cardiogenic shock after induced acute myocardial infarction. The accuracy and reliability of the prototype of the volumetric capnometer (CO2RESET™, by Eurosets srl, Medolla, Italy) device was evaluated for V′CO2ML and VDsML measurements by comparing the obtained measurements from the new device to a control capnometer with the sweep gas values. Measurements were taken at five different levels of gas flow/blood flow ratio (0.5-1.5). Agreement between the corresponding measurements was taken with the two methods. We expected that 95% of differences were between d − 1.96s and d + 1.96s. Results: In all, 120 coupled measurements from each device were obtained for the V′CO2ML calculation and 40 for the VDsML. The new capnometer mean percentage bias (95% confidence interval limits of agreement) was 3.86% (12.07-4.35%) for V′CO2ML and 2.62% (8.96-14.20%) for VDsML. A negative proportional bias for V′CO2ML estimation with the new device was observed with a mean of 3.86% (12.07-4.35%). No correlations were found between differences in the coupled V′CO2ML and VDsML measurements and the gas flow/blood flow ratio or temperature. Coupled measurements for V′CO2ML showed strong correlation (rs = 0.991; p = 0.0005), as did VDsML calculations (rs = 0.973; p = 0.0005). Conclusion: The volumetric capnometer is reliable for continuous monitoring of CO2 removal by membrane lung and VDsML calculations. Further studies are necessary to confirm these data.

Development of a CO2 Sensor for Extracorporeal Life Support Applications

“…To validate the new device in vivo, we tested the sensor in an animal model, and compared the obtained measurements with the ones taken with Medtronic Microcap Plus Capnograph. Data were collected during the execution of experiments described in [7], in which pigs with induced cardiogenic shock were undergoing ECMO procedure. Measurements from the newly developed capnometer and the reference device were taken at the MO exhaust port.…”

“…It is a well-known and established method for monitoring patient's pulmonary function in a noninvasive way, widely used in emergency situations, as well as in intensive care or during anesthesia [2][3][4][5]. Even if the traditional use of capnometry is related to the field of respiratory monitoring, the application of this measurement in extracorporeal life support (ECLS) systems such as Cardio-Pulmonary Bypass (CPB) [6], Extracorporeal Membrane Oxygenation (ECMO) [7], and Extracorporeal Carbon Dioxide Removal (ECCO 2 R) [8] has been proposed. The goal of these procedures is to add oxygen (O 2 ) and remove carbon dioxide (CO 2 ) from patient blood, which is pumped through a membrane oxygenator (MO) where, gas exchange between the blood and sweep gas in the MO takes place.…”

“…In particular, monitoring of MO performance is crucial during extracorporeal circulation procedures, as it might indicate a functional impairment due to clot formation within the MO and therefore the need for MO replacement. In this context, the analysis of CO 2 concentration in the MO exhaust can be exploited to evaluate the so-called dead space, i.e., the portion of the MO that is ventilated, but not perfused by blood, and therefore not participating in gas exchange [7]. During ECMO procedure, monitoring of MO performance may provide information regarding both the patient's lung status and the MO contribution to the global ventilation, therefore guiding the weaning process [9].…”

Non-Dispersive Near Infrared Gas Flow Cell Design for Oxygenator-Exhaust Capnometry

“…It is a common method for monitoring pulmonary function noninvasively for emergency situations, intensive care, anesthesia, and for membrane oxygenators used in extracorporeal life supports such as cardiopulmonary bypass (CPB) [2]. The measurement of CO2 removal is achieved by placing a CO2 sensor at the exhaust port of the CPB oxygenator for perfusion monitoring and evaluating the oxygenator performance [3]- [5]. This is usually done by comparing blood gases before and after the oxygenator to exhaust blood gas analysis due to the lack of a standard technique for detecting CO2 in the oxygenator's exhaust [3].…”

Novel application of indocyanine green fluorescence imaging for real‐time detection of thrombus in a membrane oxygenator

“…Assessments such as D-dimer and platelet count measurements, evaluation of the gas exchange capability of the oxygenator, and eye observation of the ECMO circuit by medical staff are routinely performed. [15][16][17][18] Eye observation is often a very important criterion for circuit replacement, but a detailed assessment for any thrombus in the blood can be very difficult. Sometimes, a thrombus may be overlooked.…”