title: A modified breathing pattern improves the performance of a continuous capnodynamic method for estimation of effective pulmonary blood flow.
abstract: In a previous study a new capnodynamic method for estimation of effective pulmonary blood flow (COEPBF) presented a good trending ability but a poor agreement with a reference cardiac output (CO) measurement at high levels of PEEP. In this study we aimed at evaluating the agreement and trending ability of a modified COEPBFalgorithm that uses expiratory instead of inspiratory holds during CO and ventilatory manipulations. COEPBFwas evaluated in a porcine model at different PEEP levels, tidal volumes and CO manipulations (N = 8). An ultrasonic flow probe placed around the pulmonary trunk was used for CO measurement. We tested the COEPBFalgorithm using a modified breathing pattern that introduces cyclic end-expiratory time pauses. The subsequent changes in mean alveolar fraction of carbon dioxide were integrated into a capnodynamic equation and effective pulmonary blood flow, i.e. non-shunted CO, was calculated continuously breath by breath. The overall agreement between COEPBFand the reference method during all interventions was good with bias (limits of agreement) 0.05 (-1.1 to 1.2) L/min and percentage error of 36 %. The overall trending ability as assessed by the four-quadrant and the polar plot methodology was high with a concordance rate of 93 and 94 % respectively. The mean polar angle was 0.4 (95 % CI -3.7 to 4.5)°. A ventilatory pattern recurrently introducing end-expiratory pauses maintains a good agreement between COEPBFand the reference CO method while preserving its trending ability during CO and ventilatory alterations.
authors.affiliation: Department of Anaesthesiology, Surgical Services and Intensive Care Medicine, Karolinska University Hospital, 171 76, Solna, Stockholm, Sweden. caroline.hallsjo-sander@karolinska.se.|Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden. caroline.hallsjo-sander@karolinska.se.
authors.forename: Caroline Hällsjö
authors.initials: CH
authors.lastname: Sander
authors.affiliation: Department of Anaesthesiology, Surgical Services and Intensive Care Medicine, Karolinska University Hospital, 171 76, Solna, Stockholm, Sweden.|Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Thorir
authors.initials: T
authors.lastname: Sigmundsson
authors.affiliation: Maquet Critical Care AB, Solna, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Hallbäck
authors.affiliation: Hedenstierna's Laboratory, Department of Surgical Sciences, Section of Anaesthesiology and Critical Care, Uppsala University, Uppsala, Sweden.|CIBER de enfermedades respiratorias (CIBERES), Instituto Carlos III, Madrid, Spain.
authors.forename: Fernando Suarez
authors.initials: FS
authors.lastname: Sipmann
authors.affiliation: Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.|Maquet Critical Care AB, Solna, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Wallin
authors.affiliation: Department of Anaesthesiology, Surgical Services and Intensive Care Medicine, Karolinska University Hospital, 171 76, Solna, Stockholm, Sweden.|Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Oldner
authors.affiliation: Department of Anaesthesiology, Surgical Services and Intensive Care Medicine, Karolinska University Hospital, 171 76, Solna, Stockholm, Sweden.|Department of Physiology and Pharmacology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Håkan
authors.initials: H
authors.lastname: Björne
mesh_terms: D000465:Algorithms; D000818:Animals; D001783:Blood Flow Velocity; D002245:Carbon Dioxide / Q000097:blood; D002302:Cardiac Output; D006439:Hemodynamics / Q000502:physiology; D008168:Lung / Q000098:blood supply* / Q000503:physiopathology; D016343:Monitoring, Intraoperative; D059035:Perioperative Period; D011650:Pulmonary Alveoli / Q000503:physiopathology; D011651:Pulmonary Artery / Q000502:physiology; D015203:Reproducibility of Results; D012119:Respiration; D013552:Swine; D013815:Thermodilution; D013990:Tidal Volume; D014465:Ultrasonics
chemical_list: D002245:Carbon Dioxide
keywords: Carbon dioxide; Cardiac output; Monitoring; Perioperative