A closer look at the innovative technique for treating painful, swollen limbs
North Carolina State University researchers have repurposed lymphedema technology—originally designed to assist humans with swollen limbs caused by excess lymph fluid—to create a medical device that can aid horses with the same condition, according to a university release.1 In a pilot study, the EQ Press device proved to be effective in facilitating fluid movement from the limbs into the lymph nodes.2 This development could potentially offer a respite for horses affected by either long-standing conditions or short-term swelling caused by immobility or injury.
“Across the board, horses are predisposed to lower limb swelling. Lymphatic flow is driven by muscle contractions that circulate lymph fluid through the lymphatic system. Horses are prone to lymphatic issues because they have very little musculature in the lower limbs," said Lauren Schnabel, DVM, PhD, Dip ACVS, Dip ACVSMR, associate professor of equine orthopedic surgery at NC State and study co-author in the release.
The condition's severity can range significantly, from brief swelling due to limited mobility to lymphangitis caused by infections that may cause scarring of the lymphatic system. Typically, owners address the condition by wrapping the limbs, applying ice, and promoting physical activity. However, these remedies usually provide only temporary relief.
“Humans suffer from the exact same type of lymphedema horses do, but the difference is that human medicine has a very effective treatment option – pneumatic compression devices,” Schnabel said. “So we wanted to create a horse-specific version of those devices and see if it would be similarly effective.”1
Schnabel collaborated with a former NC State veterinary student, Irina Perdew, DVM, to develop the EQ Press in conjunction with a company that produces human pneumatic compression devices. The complete EQ Press system is made up of custom garments that can accommodate both the front and back legs of horses. The equipment is operated by pumps that are tucked into a saddle pad, generating dynamic pressure waves that commence at the lower part of the limb and progress upward, effectively removing backflow and encouraging fluid to move upward through the limb.
“There was anecdotal data that indicated compression treatment worked well for horses, but we wanted scientific evidence that demonstrates the utility of pneumatic compression for such large animals,” Schnabel said. “So we designed the NC State pilot study.”
In the study, 6 healthy thoroughbreds were injected with a tracer isotope in their lower front limbs, a harmless sulfur colloid that is taken up and excreted through the lymphatic system. A specialized camera followed the progression of the isotope up the lymphatic system and into a lymph node in the upper limb, a process known as lymphoscintigraphy. Each horse underwent lymphoscintigraphy twice—once with treatment by the EQ Press on the front limbs and once without—randomized between treatment and control.2
In all of the EQ Press treated horses, the camera showed the tracer isotope moving from the lower limb to the lymph node in the upper limb within a 60-minute window. Of the control horses, only one showed that the tracer isotope was able to reach the lymph node.2
Overall, EQ Press treated horses had significantly accelerated lymphatic flow compared to untreated horses, recorded as both time to move out of the lower limb and also as time to reach the lymph node in the upper limb.2
“Now we have compelling evidence that pneumatic compression treatments can accelerate lymphatic flow in healthy horses,” Schnabel said. “Our next step is to study the effectiveness of the EQ Press for treatment of horses with medical conditions such as lymphedema.”