RESUMEN
BACKGROUND: We have evaluated a new method for continuous monitoring of effective pulmonary blood flow (COEPBF ), i.e. cardiac output (CO) minus intra-pulmonary shunt, during mechanical ventilation. The method has shown good trending ability during severe hemodynamic challenges in a porcine model with intact lungs. In this study, we further evaluate the COEPBF method in a model of lung lavage. METHODS: COEPBF was compared to a reference method for CO during hemodynamic and PEEP alterations, 5 and 12 cmH2 O, before and after repeated lung lavages in 10 anaesthetised pigs. Bland-Altman, four-quadrant and polar plot methodologies were used to determine agreement and trending ability. RESULTS: After lung lavage at PEEP 5 cmH2 O, the ratio of arterial oxygen partial pressure related to inspired fraction of oxygen significantly decreased. The mean difference (limits of agreement) between methods changed from 0.2 (-1.1 to 1.5) to -0.9 (-3.6 to 1.9) l/min and percentage error increased from 34% to 70%. Trending ability remained good according to the four-quadrant plot (concordance rate 94%), whereas mean angular bias increased from 4° to -16° when using the polar plot methodology. CONCLUSION: Both agreement and precision of COEPBF were impaired in relation to CO when the shunt fraction was increased after lavage at PEEP 5 cmH2 O. However, trending ability remained good as assessed by the four-quadrant plot, whereas the mean polar angle, calculated by the polar plot, was wide.
Asunto(s)
Lavado Broncoalveolar , Capnografía/métodos , Gasto Cardíaco/fisiología , Arteria Pulmonar/fisiología , Animales , Respiración con Presión Positiva , Reproducibilidad de los Resultados , PorcinosRESUMEN
BACKGROUND: It is important to be able to accurately monitor cardiac output (CO) during high-risk surgery and in critically ill patients. The invasiveness of the pulmonary artery catheter (PAC) limits its use, and therefore, new minimally invasive methods for CO monitoring are needed. A potential method is estimation of CO from endogenous carbon dioxide measurements, using a differentiated Fick's principle to determine effective pulmonary blood flow (EPBF). In this study, we aimed to validate a novel capnodynamic method (COEPBF) in a wide range of clinically relevant haemodynamic conditions. METHODS: COEPBF was studied in 10 pigs during changes in preload, afterload, CO increase, and bleeding. An ultrasonic flow probe around the pulmonary artery was used as reference method of CO determination. CO was also measured using a PAC thermodilution technique (COPAC). CO and other haemodynamic data were recorded before and during each intervention. Accuracy and precision and also the ability to track changes in CO were determined using Bland-Altman, four-quadrant plot and polar plot analysis. RESULTS: COEPBF and COPAC showed equally good agreement, with a tendency to overestimate CO (bias 0.2 and 0.3 litre min(-1), respectively). The overall percentage error was 47% for COEPBF and 49% for COPAC. The concordance for tracking CO changes was 97 and 95% for COEPBF and COPAC, respectively, with an exclusion zone of 15% and radial limits of ±30°. CONCLUSIONS: COEPBF showed reliable trending abilities, equivalent to COPAC. COEPBF and COPAC also showed low bias but high percentage errors. Further studies in animal models of lung injury and in high-risk surgery patients are warranted.
Asunto(s)
Capnografía/métodos , Dióxido de Carbono/análisis , Gasto Cardíaco/fisiología , Hemodinámica/fisiología , Monitoreo Fisiológico/métodos , Respiración Artificial , Animales , Velocidad del Flujo Sanguíneo/fisiología , Dióxido de Carbono/metabolismo , Modelos Animales , Monitoreo Intraoperatorio/métodos , Monitoreo Intraoperatorio/estadística & datos numéricos , Monitoreo Fisiológico/estadística & datos numéricos , Arteria Pulmonar/diagnóstico por imagen , Arteria Pulmonar/fisiología , Reproducibilidad de los Resultados , Porcinos , Termodilución/métodos , Termodilución/estadística & datos numéricos , UltrasonografíaRESUMEN
BACKGROUND: Goal-directed fluid therapy improves outcome in major surgery. We evaluated a new device (LiDCOrapid) against our standard oesophageal Doppler method (ODM) for stroke volume (SV) optimization during colorectal surgery. METHODS: This was an observational study in 20 patients undergoing major colorectal surgery within a fast-track protocol. We compared SV values measured simultaneously by LiDCOrapid and ODM before and after 86 fluid challenges. We also evaluated the LiDCOrapid dynamic indices SV variation (SVV) and pulse pressure variation (PPV) as predictors for volume responsiveness, defined as an increase in SV ≥ 10% after 200 ml of colloid. RESULTS: SV increased ≥ 10% after 27 out of 86 fluid challenges. For 172 paired SV values, the overall correlation was r=0.39, and bias (limits of agreement) -28 (-91-35) ml, percentage error 70%. The ability of LiDCOrapid to track changes in SV was weak with a concordance rate of 80%, and a sensitivity and specificity of 48% and 81%, respectively, to detect a positive fluid challenge. The area under the curve values (with 95% confidence intervals) for SVV and PPV were 0.72 (0.60-0.83) and 0.66 (0.52-0.79), respectively, indicating low predictive capacity in these setting. CONCLUSIONS: LiDCOrapid and ODM devices are not interchangeable. We cannot recommend that the LiDCOrapid replace the standard Doppler method until further device-specific outcome studies on volume optimization are available. The dynamic indices SVV and PPV add little value to a fluid optimization protocol, and should not replace SV measurements with a validated technique.