Use of Electrical Impedance Tomography (EIT) to Estimate Tidal Volume in Anaesthetized Horses Undergoing Elective Surgery.
Authors: Crivellari Benedetta, Raisis Anthea, Hosgood Giselle, Waldmann Andreas D, Murphy David, Mosing Martina
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Electrical Impedance Tomography for Tidal Volume Monitoring in Anaesthetised Horses Accurate tidal volume measurement during equine general anaesthesia remains challenging in clinical practice, prompting investigation into non-invasive alternatives to traditional spirometry. Researchers anaesthetised 17 healthy horses undergoing elective dorsal recumbency procedures and systematically compared electrical impedance tomography (EIT)—which detects impedance changes across the thorax with each breath—against spirometric measurements across varying ventilatory settings (10, 12 and 15 mL/kg). Whilst individual horses demonstrated marked variation in the mathematical relationship between impedance change and actual tidal volume, each animal showed exceptionally strong correlations (R² 0.9–0.99) when analysed separately, and estimated volumes agreed well with spirometric values (bias 0.26 L, limits of agreement −0.36–0.88 L). The findings indicate that EIT can provide reliable real-time tidal volume monitoring during equine anaesthesia, provided clinicians first establish the patient-specific calibration curve at the start of each procedure—a practical consideration that may limit widespread adoption but could prove valuable in high-risk cases or where spirometry is unavailable. This technology warrants further investigation under field conditions and with horses of varying body condition to determine clinical utility in everyday equine practice.
Read the full abstract on PubMed
Practical Takeaways
- •EIT offers a non-invasive method to estimate tidal volume during equine anaesthesia, potentially improving ventilation monitoring during dorsal recumbency procedures
- •Individual calibration is essential—each horse requires baseline measurements at known tidal volumes before EIT can accurately estimate subsequent breaths
- •Good agreement between EIT estimates and measured tidal volume suggests this technology could help clinicians maintain appropriate end-tidal CO₂ targets during routine surgical cases
Key Findings
- •Strong positive correlation (R² 0.9-0.99) found between impedance change per breath (ΔZbreath) and spirometric tidal volume in individual horses
- •EIT-estimated tidal volume (VTEIT) showed good agreement with measured spirometric tidal volume (VTSPIRO) with bias of 0.26 L (LOA -0.36–0.88 L)
- •Marked variability in slope and intercepts observed across horses, requiring individual calibration before clinical application
- •EIT can be used to monitor and estimate tidal volume in anaesthetised horses after establishing individual ΔZbreath-VT relationships