(E56) Three-dimensional Thoracic Electrical Impedance Tomography of Horses During Normal and Increased Tidal Volumes

Background: Electrical impedance tomography (EIT) is a non-invasive method of evaluating lung function.
 


Objective: To describe multiplanar reconstruction of two-plane EIT data and assess correspondence of distribution of ventilation with known anatomical topography
 
Animals: Twenty clinically healthy research horses
 


Methods: Two-plane EIT data were collected in standing sedate horses at baseline (resting) conditions, and during rebreathing. EIT data were reconstructed into 3d EIT whereby tidal impedance variation (TIV), ventilated area, and right-left (CoV_RL) and ventral-dorsal (CoV_VD) centres of ventilation  were calculated in cranial, middle and caudal slices of lung. A two-factor general linear model was applied with time (baseline and rebreathing), slice and the interaction included as fixed effects. Where significant interaction was found, at p < 0.05.
 


Results: There was a significant interaction of time and slice for TIV (p < 0.0001) with TIV increasing during rebreathing in caudal and middle slices. The ratio of right to left ventilated area was higher in the cranial slice, in comparison to the caudal slice (p = 0.0002).  There were significant effects of time and slice on CoV_VD whereby the cranial slice was more ventrally distributed than the caudal slice (p < 0.0009 for the interaction).  
 
Conclusions and clinical importance: The distribution of ventilation in the three slices corresponds with topographical anatomy of the equine lung. This study confirms that 3d EIT represents lung anatomy and changes in ventilation distribution during increased tidal volume breathing in standing sedate horses.