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Performance of a capnodynamic method estimating effective pulmonary blood flow during transient and sustained hypercapnia.

ABSTRACT: The capnodynamic method is a minimally invasive method continuously calculating effective pulmonary blood flow (CO_EPBF), equivalent to cardiac output when intra pulmonary shunt flow is low. The capnodynamic equation joined with a ventilator pattern containing cyclic reoccurring expiratory holds, provides breath to breath hemodynamic monitoring in the anesthetized patient. Its performance however, might be affected by changes in the mixed venous content of carbon dioxide (C_vCO₂). The aim of the current study was to evaluate CO_EPBF during rapid measurable changes in mixed venous carbon dioxide partial pressure (P_vCO₂) following ischemia-reperfusion and during sustained hypercapnia in a porcine model. Sixteen pigs were submitted to either ischemia-reperfusion (n?=?8) after the release of an aortic balloon inflated during 30 min or to prolonged hypercapnia (n?=?8) induced by adding an instrumental dead space. Reference cardiac output (CO) was measured by an ultrasonic flow probe placed around the pulmonary artery trunk (CO_TS). Hemodynamic measurements were obtained at baseline, end of ischemia and during the first 5 min of reperfusion as well as during prolonged hypercapnia at high and low CO states. Ischemia-reperfusion resulted in large changes in P_vCO₂, hemodynamics and lactate. Bias (limits of agreement) was 0.7 (-0.4 to 1.8) L/min with a mean error of 28% at baseline. CO_EPBF was impaired during reperfusion but agreement was restored within 5 min. During prolonged hypercapnia, agreement remained good during changes in CO. The mean polar angle was -4.19° (-8.8° to 0.42°). Capnodynamic CO_EPBF is affected but recovers rapidly after transient large changes in P_vCO₂ and preserves good agreement and trending ability during states of prolonged hypercapnia at different levels of CO.

SUBMITTER: Sigmundsson TS

PROVIDER: S-EPMC5838142 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Performance of a capnodynamic method estimating effective pulmonary blood flow during transient and sustained hypercapnia.

Sigmundsson Thorir Svavar TS Öhman Tomas T Hallbäck Magnus M Redondo Eider E Sipmann Fernando Suarez FS Wallin Mats M Oldner Anders A Hällsjö Sander Caroline C Björne Håkan H

Journal of clinical monitoring and computing 20170511 2

The capnodynamic method is a minimally invasive method continuously calculating effective pulmonary blood flow (CO<sub>EPBF</sub>), equivalent to cardiac output when intra pulmonary shunt flow is low. The capnodynamic equation joined with a ventilator pattern containing cyclic reoccurring expiratory holds, provides breath to breath hemodynamic monitoring in the anesthetized patient. Its performance however, might be affected by changes in the mixed venous content of carbon dioxide (C<sub>v</sub> ...[more]

PMID: 28497180

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Project description:BackgroundCardiac output (CO) monitoring is the basis of goal-directed treatment for major abdominal surgery. A capnodynamic method estimating cardiac output (COEPBF) by continuously calculating nonshunted pulmonary blood flow has previously shown good agreement and trending ability when evaluated in mechanically ventilated pigs.ObjectivesTo compare the performance of the capnodynamic method of CO monitoring with transpulmonary thermodilution (COTPTD) in patients undergoing major abdominal surgery.DesignProspective, observational, method comparison study. Simultaneous measurements of COEPBF and COTPTD were performed before incision at baseline and before and after increased (+10 cmH2O) positive end-expiratory pressure (PEEP), activation of epidural anaesthesia and intra-operative events of hypovolemia and low CO. The first 25 patients were ventilated with PEEP 5 cmH2O (PEEP5), while in the last 10 patients, lung recruitment followed by individual PEEP adjustment (PEEPadj) was performed before protocol start.SettingKarolinska University Hospital, Stockholm, Sweden.PatientsIn total, 35 patients (>18 years) scheduled for major abdominal surgery with advanced hemodynamic monitoring were included in the study.Main outcome measures and analysisAgreement and trending ability between COEPBF and COTPTD at different clinical moments were analysed with Bland--Altman and four quadrant plots.ResultsIn total, 322 paired values, 227 in PEEP5 and 95 in PEEPadj were analysed. Respectively, the mean COEPBF and COTPTD were 4.5 ± 1.0 and 4.8 ± 1.1 in the PEEP5 group and 4.9 ± 1.2 and 5.0 ± 1.0 l min-1 in the PEEPadj group. Mean bias (levels of agreement) and percentage error (PE) were -0.2 (-2.2 to 1.7) l min-1 and 41% for the PEEP5 group and -0.1 (-1.7 to 1.5) l min-1 and 31% in the PEEPadj group. Concordance rates during changes in COEPBF and COTPTD were 92% in the PEEP5 group and 90% in the PEEPadj group.ConclusionCOEPBF provides continuous noninvasive CO estimation with acceptable performance, which improved after lung recruitment and PEEP adjustment, although not interchangeable with COTPTD. This method may become a tool for continuous intra-operative CO monitoring during general anaesthesia in the future.Trial registrationClinicaltrials.gov identifier: NCT03444545.

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Performance of a capnodynamic method estimating effective pulmonary blood flow during transient and sustained hypercapnia.

Publications

Performance of a capnodynamic method estimating effective pulmonary blood flow during transient and sustained hypercapnia.

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