Tool harnesses air flow in real time

EIT technology allows anesthesiologists to better understand breathing patterns in sedated or anesthetized horses. Photo: Christina Weese.

Researchers at the Western College of Veterinary Medicine (WCVM) are collaborating with Andy Adler, a Canada Research Professor in Biomedical Engineering at Carleton University, to use a new technique called electrical impedance tomogrophy (EIT).

This non-invasive technology is appealing to veterinary specialists because it will allow them to better understand the changes in breathing patterns happening in sedated and anesthetized horses. The WCVM is one of only a few places in the world working with this new technology on horses, the others being research institutions in Vienna, Zurich and London.

One of the biggest difficulties when performing surgeries on a horse is its massive size. Surgeries can be done while the horse is standing and sedated, but it’s easier for veterinarians to perform surgeries while the horse is lying down and anesthetized. However, this can lead to complications for the animal.

“[Horses] are prone to changes in ventilation patterns when they are anesthetized,” says Dr. Tanya Duke, a specialist in anesthesia at the WCVM. “Their lungs get compressed because they’re not designed to be on their backs for long periods of time.”

In research publications, EIT is described as using direct contact electrical stimulation and measurement at the body surface to image the electrical properties of internal tissues, such as lungs. When used on horses, researchers place a belt of 32 electrodes around the thorax, or chest, of the animal. As electrical currents pass between the electrodes, they detect any changes or restrictions (within the belt’s range) in the horse’s airways

Using specialized software, these measurements create a pixelated picture of the horse’s lung aeration in real time. It also shows the formation of atelectasis — a partial or complete collapse of a lung or lobe of a lung.

Right now, veterinary anesthesiologists can only measure how efficiently an anesthetized horse’s lungs are performing by taking arterial blood samples and analyzing them for oxygen and carbon dioxide levels — a process that takes time, energy and money.

“Putting a catheter into an artery to get access to the blood is an intermittent measurement, whereas the other method [EIT] is continuous so you are constantly getting a picture,” says Duke. “With blood samples, you have to physically take the sample to an analyzer and you only get a snapshot of what’s going on.”

Adler, who developed an EIT belt for equine patients, is internationally known for his extensive EIT research with horses and people. In May 2017, Adler visited the WCVM and demonstrated the belt’s use on a standing, sedated horse for Duke and her colleagues.

Duke says the biggest obstacle is learning how to use the technology to get the best results. As a first step, she and her team are using the EIT belt to track lung compression in standing, sedated horses while carbon dioxide is pumped in to inflate the abdomen.

“Once we know if it can pick up that amount of lung collapse [in sedated horses], it will definitely pick up the lung collapse in an anesthetized horse, which is going to be so much more,” says Duke.

The researchers’ eventual goal is to develop a reliable way to use the belt on an anesthetized horse without it slipping or shifting as the animal is hoisted off the ground.

“We’re just developing the technology in the standing horses and learning how to use it, to move on to using it in the anesthetized horse. But that will be down the road,” says Duke. “I think the Vienna group [researchers] have done a couple of cases where they’ve used it on anesthetized horses and you can see that there is lung collapse on their images.”

Another challenge is the electrode belt’s size. It’s only a couple inches wide and has just two rings of electrodes, which means the area it monitors is only a small portion of the horse’s entire lung and airway.

“We’re only looking at one segment of the lung whereas we really would like to be looking at the whole lung, so that would mean lots of rings of electrodes and a bigger belt,” says Duke.

She credits Dr. Charlotte Marly-Voquer, a former clinical associate in the WCVM’s Veterinary Medical Centre, as the person who was instrumental in connecting the WCVM with this exciting new area of research.

“It’s a sad story, actually,” says Duke. “Charlotte joined us a few years ago and she had done her anesthesia residency in Zurich and had used the belt over there. She wanted to continue that research while she was here and she asked me to be the faculty co-investigator for her to get research funds.

“Charlotte unfortunately had a brain tumour and she’s passed away from it, so her replacement Rocia [Dr. Maria del Rocia Fernandez Parra] joined us and was also very keen to take this on and so I kind of got involved that way.”

Fernandez Parra has since left the team and is now working in Paris, but she plans to return to Canada in 2019 to continue helping with the research during the next round of trials.

Until then Duke and her co-investigators, Drs. Joe Bracamonte and Masako Fujiyama, are continuing work on the research project with Adler’s collaboration. The WCVM team’s efforts are supported by a research grant from the WCVM’s Townsend Equine Health Research Fund (TEHRF).

Harrison Brooks of Fort Qu’Appelle, Sask., is a third-year student at the University of Regina’s School of Journalism. Harrison is the summer research communications intern at the WCVM.