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Performance of a revised capnodynamic method for cardiac output monitoring

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posted on 2024-09-03, 04:46 authored by Thorir Sigmundsson

Cardiac output (CO) monitoring is ideal for guiding fluid, vasopressor and inotropic therapy for sufficient oxygen delivery and may improve outcome in high risk surgery. In this context, many minimally-and non-invasive methods have emerged during recent years, however, they appear less reliable when compared to the thermodilution methods during rapid changes in vascular volume and resistance, a common feature during major surgery. The capnodynamic method calculates non-shunted cardiac output, the effective pulmonary blood flow (COEPBF), on the basis of a capnodynamic equation describing the mole balance of CO2 transported to and from the lungs. By prolonging three out of every nine breaths in mechanically ventilated patients, COEPBF is automatically and continuously calculated with each new breath. In previous studies the capnodynamic method with inspiratory holds provided CO mon-itoring, however with unacceptable accuracy and precision during lung injury and elevated positive end-expiratory pressure (PEEP).

In this thesis we evaluated the revised capnodynamic method with expiratory holds in four separate studies. In a large animal model (study I-III), COEPBF was compared to a gold stan-dard flowmeter placed around the pulmonary trunk during different hemodynamic, ventila-tory, respiratory and metabolic challenges. Finally, COEPBF was compared to transpulmonary thermodilution in patients undergoing high risk abdominal cancer surgery. The capnodynamic method showed overall acceptable agreement and good trending abil-ities in a variety of conditions familiar to a perioperative team. The agreement was tempo-rarily disrupted after ischemia-reperfusion, however reestablished within five minutes. The accuracy was marginally affected during lung injury, both at high shunt fractions and after recruitment manoeuvre with PEEP adjustment. However, both precision and trending ability were maintained. In high risk patients, COEPBF showed good accuracy, acceptable precision and good trending ability in various conditions. The performance was especially robust after individualized lung recruitment and PEEP adjustment. COEPBF may provide continuous CO monitoring with short response time, good trending abilities and acceptable agreement to guide hemodynamic treatment during surgery.

List of scientific papers

I. A modified breathing pattern improves the performance of a continuous capnodynamic method for estimation of effective pulmonary blood flow. Sander CH, Sigmundsson T, Hallbäck M, Sipmann FS, Wallin M, Oldner A, Björne H. J Clin Monit Comput. 2017;31(4):717-725.
https://doi.org/10.1007/s10877-016-9891-z

II. Performance of a capnodynamic method estimating effective pulmonary blood flow during transient and sustained hypercapnia. Sigmundsson TS, Öhman T, Hallbäck M, Redondo E, Sipmann FS, Wallin M, Oldner A, Hällsjö Sander C, Björne H. J Clin Monit Comput. 2018;32(2):311-319.
https://doi.org/10.1007/s10877-017-0021-3

III. The performance of a modified capnodynamic method in respiratory failure and after lung recruitment. Sigmundsson TS, Öhman T, Hallbäck M, Redondo E, Sipmann FS, Wallin M, Oldner A, Hällsjö Sander C, Björne H. [Manuscript]

IV. The performance of the capnodynamic method for cardiac output monitor-ing during major abdominal surgery. Sigmundsson TS, Öhman T, Hallbäck M, Wallin M, Sipmann FS, Oldner A, Hällsjö Sander C, Björne H. [Manuscript]

History

Defence date

2019-05-17

Department

  • Department of Physiology and Pharmacology

Publisher/Institution

Karolinska Institutet

Main supervisor

Björne, Håkan

Co-supervisors

Hällsjö Sander, Caroline; Oldner, Anders

Publication year

2019

Thesis type

  • Doctoral thesis

ISBN

978-91-7831-381-5

Number of supporting papers

4

Language

  • eng

Original publication date

2019-04-25

Author name in thesis

Sigmundsson, Thorir

Original department name

Department of Physiology and Pharmacology

Place of publication

Stockholm

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