“Equine asthma” is now recognised as a diagnosis that encompasses both inflammatory airway disease (with less severe signs, virtually unnoticeable when the horse is at rest) and recurrent airway obstruction or heaves (with increased breathing efforts at rest and chronic coughing).
Dr Laurent Couëtil and his colleagues at the Purdue University College of Veterinary Medicine have developed a new technique to overcome the challenge of testing equine pulmonary function.
“Milder equine asthma has been difficult to detect because horses don’t necessarily show many signs besides the fact that they’re not performing well. Some of them cough once in a while, but it isn’t crippling them,” Couëtil said. “Now that we have the tools to look for it, we realize it’s very common.”
|In a study 80% racehorses had signs of asthma ((c) Purdue university/Rebecca Wilcox)|
To test for equine asthma, veterinarians use variations of methods developed to measure lung disease and dysfunction in humans, such as the bronchoalveolar lavage and lung function test. However, some of these tests are not commonly done or are impossible to perform on horses.
“In humans, the most common test performed to test for asthma is forced exhalation. The nurse trains you to take in the deepest breath possible and blow out as hard as you can,” he said. “This is easy for people because we can follow instructions, but you can’t tell a horse to do that, so I worked with Purdue engineers to develop a pulmonary function test for horses.”
The test uses a mechanical ventilator to control a sedated horse’s breathing. A series of tanks, using positive and negative pressure, help mimic deep inhalation and exhalation. During the process, a computer records data about the patient’s lung capacity, expiration volume and expiration flow. This system is the only one in the world capable of performing such a test, and is extremely sensitive, detecting even very mild asthma. The equine pulmonary function test technology is patented through Purdue’s Office of Technology Commercialization.
Currently, the equipment is too large to be used other than in the hospital. It also requires specialised expertise to operate it. The lab is working to develop a more simplified and portable system that could be used by ambulatory veterinarians to diagnose asthma in the field.