Comparison of Cardiac Index (CI) Measurements Performed With Use of the Bioreactance Technology and Transpulmonary Thermodilution in Reference to Measurements Based on Echocardiography.

After approval of the study design by the institutional ethics committee, 50 critically ill adult patients (requiring haemodynamic monitoring and mechanical ventilation) treated in the ICU for a intracranial pathology will be enrolled in the study.

Exclusions: Age under 18, presence of pleural effusion or pericardium (confirmed by chest X-ray and / or ultrasound / echocardiography), presence of aortic / mitral valve disease, presence of an implanted pacemaker CI measurements will be performed simultaneously for 5 minutes. The CI value measured by the transpulmonary thermodilution technique will be obtained with the PiCCO system (Pulsiocat PV8115; Pulsion Medical Systems, Feldkirchen, Germany). Measurements will be made three times within 5 minutes. For statistical purposes, the value of the arithmetic mean of the obtained results will be used.

The CI value as measured by the bioreactance method will be determined using the monitor: Starling Fluid Management System (Baxter International Inc, USA). This monitor uses bioreactance technology to determine hemodynamic parameters and bioimpedance technology to measure thoracic fluid content (TFC). The test data will be recorded with two pairs of electrodes placed on the chest according to the manufacturer's instructions. Measurements documented at 30-second intervals will concern 10 measurement cycles. The average of the obtained results will be subjected to statistical analysis.

Echocardiographic examination of the heart to determine the value of CI will be performed by one (always the same) qualified (certified in echocardiographic examinations) clinician.

Echocardiographic measurements will begin with determining the diameter of the left ventricular outflow tract (left ventricular outflow tract cross-sectional area, LVOT-CSA). Then, three subvalvular velocity time integral (LVOT-VTI) measurements will be made over the course of 5 minutes. This measurement will be performed in the apical five-chamber projection.