Variety of non-invasive continuous monitoring methodologies including electrical impedance tomography provides novel insights into the physiology of lung collapse and recruitment – case report of an anaesthetized horse.

The research article shares details of an experiment involving the usage of non-invasive continuous monitoring methodologies like electrical impedance tomography to understand lung collapse and recruitment during general anesthesia of a horse. It specifically looks at how these technologies could enhance ventilatory management in large animals.

Research Methodology and Experimentation

• The researchers conducted their experiment on a healthy 533 kg horse. This horse was subjected to general anesthesia while in lateral recumbency, a common position to induce anesthesia in large animals, that has the animal lying on its side.
• The team induced anesthesia in the horse using a combination of two medications, Ketamine and Midazolam. They then maintained the anesthetic state using Isoflurane, delivered in oxygen, via a large animal circle system.
• Once the horse was under the effect of anesthesia, it was subjected to a form of pressure ventilation known as intermittent positive pressure ventilation.
• As a part of the experiment, a stepwise alveolar recruitment maneuver was performed. This procedure involved a systematic increase and decrease in end expiratory pressures while monitoring respiratory performance in the horse.

Innovative Monitoring Techniques Utilized

• The researchers used three non-invasive monitoring techniques: Electrical Impedance Tomography (EIT), Volumetric Capnography, and Respiratory Ultrasonic Plethysmography.
• EIT proved to be particularly useful as it generated continuous functional images showing ventilation in the dependent lung. In addition to standard monitoring and spirometry, these images enabled real-time monitoring of dynamic changes in ventilation distribution during the recruitment maneuver.
• The other two techniques allowed for continuous monitoring of other key aspects such as lung compliance, tidal volumes and changes in end expiratory lung volume. Dead space fraction measurements could also be made without facing any technical difficulties.

Result and Conclusions

• The subject of the experiment, the horse, went through the entire process without any complications and made an unremarkable recovery after the procedures were complete.
• Based on this experiment, the researchers concluded that the non-invasive technologies provided new insights into lung collapse and recruitment physiology, the process by which air sacs in the lungs are opened and closed.
• The study suggests that this synergistic combination of techniques could hold promise in supporting the development and evaluation of new ventilatory strategies in horses.