PURRcision: Pulse oximeters for Frankie’s Friends

Every fall, a group of mostly seniors takes a course called Foundation of Biomedical Engineering (BME) Design where engineering students learn to assess product needs for biomedical applications. In the spring they take the follow-up course, BME Design Projects. Students are grouped into teams and work through the processes they learned about in the prior semester, eventually prototyping and creating a product that can be tested in real-world applications.

This past academic year, groups of students studied under Rachelle Palchesko to complete their project course. One group was assigned to work with Becky Morrow of Frankie’s Friends, a local non-profit that focuses on veterinary and rescue services for cats and other animals. The student group consisted primarily of seniors majoring in chemical engineering (ChemE), electrical and computer engineering (ECE), and materials science and engineering (MSE) who are seeking additional majors in BME.

Morrow was already familiar with Carnegie Mellon, as Frankie’s Friends occasionally brings rescue kittens and cats to campus for Study Break with Cats, a de-stress event hosted by the Department of Chemical Engineering where students can play with the cats, providing a moment of tranquility for the students and human socialization for the hopeful future pets. “I’ve actually been to all of them,” said team member Cindy Jiang, “It was a pretty fun de-stress event right before finals.”

As her main occupation, Morrow is the president and medical director of Frankie’s Friends, where she oversees high-quality, high-volume spay/neuter (HQHVSN) services. During HQHVSN services, multiple cats are put under anesthesia all at once to be operated on in one session. This makes spaying and neutering much more time- and cost-efficient for the non-profit that services about 500 cats per year.

While they are under anesthesia, it is important to monitor the cats for blood pressure, pulse, and blood oxygenation levels. In some surgeries, these readings are achieved by attaching devices to tongues or ears or inserting them in their throats. However, during these HQHVSN sessions, the cats wear small masks for anesthesia delivery, making it difficult to access those areas around the face. Paws are another option, but only for some of the cats. Morrow explains, “For the pink-toed kitties, we use little paw pads, and we use our pulse oximeters there.” However, many of the cats have dark paws, and the devices cannot get accurate readings through the pigmentation.

This leaves the back end of the cat as one of the only options. Therefore, these students took on the challenge of developing a rectal pulse oximeter for cats which they titled PURRcision.

There are currently other feline rectal pulse oximeters on the market. Morrow shares that the ones that Frankie’s Friends already uses are not well-designed. “They are not easy to disinfect, and especially in a nonprofit situation, we can't spend $85 on a piece of equipment that lasts only four times.”

The group started with a literature review, looking at existing models and talking about what has worked or not in the past, and by consulting Morrow. Team member Jimmy Kim shared, “We talked with Dr. Morrow and she gave us some guidelines, like durability of the pulse oximeter. We also talked about [a device] that works for all types of cats.” From there they developed a needs statement, pinpointing what they’d like to accomplish. And then they took to labs and maker spaces, developing CAD models, 3D-printing prototypes, and developing tiny electronics.

The team was also able to do physical endurance tests on the external casing of the oximeter, such as dropping it from a table height, simulating what can happen in a veterinary office. They also tested for things like an animal biting it. Nik Firestone explained, “One of the tests is called a three-point test, where you break it and see how much force it can withstand before it breaks.”

The students were excited to present their poster and their prototype at the Meeting of the Minds Undergraduate Research Symposium, which CMU hosts annually at the end of the spring semester. Team member Sara Gibson explained that, although they didn’t have time this semester to be able to test on cats, they were still able to test their electronics’ ability to take pulses. Visitors to their poster could place their fingers on a device that would read their pulse, much like at a doctor’s office check-up.

Morrow was excited to work with the students as part of their process. “They're wonderful, and they all have really good questions and insight. I feel like it's a real collaborative effort.” She hopes that Frankie’s Friends can continue to partner with the BME Design Projects course—and of course to keep bringing kittens to campus for de-stress events.