Validation of three-dimensional thoracic electrical impedance tomography of horses during normal and increased tidal volumes.

The researchers have been testing the accuracy of a three-dimensional imaging method called electrical impedance tomography, more specifically used to visualize lung functioning in horses. They found this method to be a valid tool, specifically when monitoring changes in the lung during differing states of ventilation or breathing.

Research Approach

• In this study, the researchers used a method known as electrical impedance tomography (EIT). This is a non-invasive, radiation-free imaging technique that can provide a three-dimensional (3D) view of an organ, in this instance, the lungs of horses.
• The researchers applied this technique to 20 horses that were standing and sedated. They used this method during standard resting conditions and during an exercise called ‘rebreathing’, a training maneuver used to increase a horse’s breathing or ventilation.
• They used two electrode sets placed 20 centimeters apart on the horses’ chests. From the data collected, they created 3D images of the lungs, allowing them to analyze various properties such as ventilated areas, variation in tidal volume (the amount of air moving in and out of the lungs during normal breathing), and the centers of ventilation.

Main Results

• The researchers noted a significant change over time for tidal impedance variation (TIV), the measure of air volume change, during the rebreathing exercise. The TIV increased, indicating an increase in air volumes in the caudal (lower) and middle sections of the lung.
• Additionally, they found that the right-to-left ventilated area ratio was higher in the upper (cranial) section of the lungs compared to the lower (caudal) section.
• Furthermore, the cranial section of the lung was more ventrally (towards the belly) distributed than the caudal section. This was measured by a term known as CoVVD or the ventral-dorsal centers of ventilation distribution.

Significance

• The researchers concluded that the ventilated areas in the three lung sections corresponded to the typical anatomical structure of the equine lung. This finding confirmed the accuracy of the 3D EIT technique in representing lung anatomy and displaying changes in ventilation distribution before and during rebreathing activity in horses.
• The successful validation of this methodology shows its potential application in future research, enabling non-invasive, detailed investigation of equine lung function under different physiological states. This could provide valuable insights into normal lung function as well as in the study of equine respiratory diseases.