Use of Electrical Impedance Tomography (EIT) to Estimate Tidal Volume in Anaesthetized Horses Undergoing Elective Surgery

oleh: Benedetta Crivellari, Anthea Raisis, Giselle Hosgood, Andreas D. Waldmann, David Murphy, Martina Mosing

Format: Article
Diterbitkan: MDPI AG 2021-05-01

Deskripsi

This study explores the application of electric impedance tomography (EIT) to estimate tidal volume (VT) by measuring impedance change per breath (∆Z<sub>breath</sub>). Seventeen healthy horses were anaesthetised and mechanically ventilated for elective procedures requiring dorsal recumbency. Spirometric VT (VT<sub>SPIRO</sub>) and ∆Z<sub>breath</sub> were recorded periodically; up to six times throughout anaesthesia. Part 1 assessed these variables at incremental delivered VT of 10, 12 and 15 mL/kg. Part 2 estimated VT (VT<sub>EIT</sub>) in litres from ∆Z<sub>breath</sub> at three additional measurement points using a line of best fit obtained from Part 1. During part 2, VT was adjusted to maintain end-tidal carbon dioxide between 45–55 mmHg. Linear regression determined the correlation between VT<sub>SPIRO</sub> and ∆Z<sub>breath</sub> (part 1). Estimated VT<sub>EIT</sub> was assessed for agreement with measured VT<sub>SPIRO</sub> using Bland Altman analysis (part 2). Marked variability in slope and intercepts was observed across horses. Strong positive correlation between ∆Z<sub>breath</sub> and VT<sub>SPIRO</sub> was found in each horse (R<sup>2</sup> 0.9–0.99). The agreement between VT<sub>EIT</sub> and VT<sub>SPIRO</sub> was good with bias (LOA) of 0.26 (−0.36–0.88) L. These results suggest that, in anaesthetised horses, EIT can be used to monitor and estimate VT after establishing the individual relationship between these variables.