Entering Randy Stroetz's office at Mayo Clinic is like walking into a machine shop. In the corner squat a gigantic lathe and a machine for milling metal and plastic. Cabinets overflow with cans of WD-40, and hand-made devices sprouting wires, batteries and plastic tubing clutter the desk. Shelves of books and slick computers attest to the fact that, yes, a Mayo clinical specialist indeed works here. But this is a clinical specialist like none other.

With no formal training in biomedical engineering, Mr. Stroetz designs and builds devices that allow Mayo researchers to study lung function with far greater precision and power than is possible with commercially available instruments. "Randy is a Renaissance man," says Rolf Hubmayr, M.D., director of the lab for which Mr. Stroetz produces most of his devices. "He can think outside the box. He truly is an inventor."

A self-effacing man, Mr. Stroetz considers himself more a "third violinist" in the pulmonary lab. But he shows justifiable pride when describing accomplishments from his 28 years at Mayo.

One of his best-known inventions is the "cell stretcher," used by researchers seeking to prevent ventilator-induced lung injury. Although most patients suffer no long-term effects from being put on a mechanical ventilator, injuries can occur under certain circumstances. To find out why, Mayo researchers wanted to examine what happens to lung cells when they are stretched in the lab. An existing commercial system allowed researchers to grow cells on a stretchable membrane. But "that device had a lot of limitations," Mr. Stroetz says. It was vacuum-driven, so the "stretch" imparted to the cells wasn't uniform. The vacuum sometimes developed leaks and the machine had no mechanism to alert researchers to such faults. "So people's experiments were very hit or miss," Mr. Stroetz says.

Inspired by his love of music, Mr. Stroetz decided to eliminate the vacuum and, instead, stretch the membrane mechanically using a small electric motor. The son of a professional musician, he liked to "mess around" with the instruments in his childhood home "while nobody was around." He was especially intrigued with the timpani or kettle drum. Timpani emit a definite pitch when struck; when a timpani's foot pedal is depressed, a connecting mechanism alters the drumhead's tension and changes the pitch.

"We use that same mechanical system to stretch cells that are grown on a stretchable membrane," Mr. Stroetz says. "It allows us to do things you couldn't do with the (existing) machines. I'm very proud of that."

Many of Mr. Stroetz's devices use software written by Bruce Walters, another lab-team member, with whom he shares the cluttered office. "Randy is the idea guy," Mr. Walters says. "He comes up with a device that we think we can build, then he'll find the components" to build a prototype.

That search for parts once sent Mr. Stroetz burrowing through the Mayo archives for an iron lung formerly used for polio patients. He recalls Mayo researchers' telling him they needed a sealed chamber in which study participants' breathing could be precisely measured during sleep. Existing instruments were inaccurate or so intrusive that sleep was impossible. After weeks spent repairing leaks in the old iron lung, Mr. Stroetz used a bicycle inner tube to seal the opening where the bed slid in. "And that worked very well," he says.

Another custom-built tool is the "laser trap," which allows researchers to make tiny manipulations in cell membranes and to measure the results. Such precision wasn't possible with existing instruments. But using software written by Mr. Walters, Mr. Stroetz introduced a laser into the optical path of a very powerful microscope. The laser's light force moves certain minute particles which in turn react with the cells being examined, tugging on their membranes. "This tells us about the properties of the cell membrane, which determine whether the cell gets wounded during a breath or not," Dr. Hubmayr says.

A respiratory therapist and registered nurse, Mr. Stroetz started his career at Mayo caring for patients in the emergency room and intensive-care units, before moving to the pulmonary-research lab in 1991. "He could not be satisfied with just providing superb clinical care," says Curtis F. Buck, director of Mayo's Respiratory Care Service. "He had to start digging into research. He has the most overwhelming curiosity of anyone I know."

That curiosity can make him "frustrating" to work with, Mr. Buck adds with a laugh. "Randy is very contemplative. At times, you want to just shake him. But he always comes up with an answer." Mr. Buck credits Mayo with giving Mr. Stroetz freedom to create. The Mayo brothers encouraged innovation, he says, and "Mayo is still a place where you can invent yourself. People can find their way to an incredible career with their special gifts, so long as it helps the patient. Randy has done that."

Outside the lab, Mr. Stroetz's building projects include a restored 1950 Beechcraft Bonanza aircraft (which he occasionally pilots), his three-bedroom home (he designed it, and did all the plumbing, heating and electrical work) and his family's cars (all rebuilt from salvage). "The latest is a nearly new Toyota Prius, which was an interesting way to learn hybrid technology firsthand," Mr. Stroetz says. He also finds time to play trombone with a local band.

But most of his time nowadays is spent dreaming up new devices. One current idea is a sort of souped-up hearing aid; besides amplifying sound, it would use wireless communication to stream data such as the wearer's physical position and vital signs, thus alerting monitors if an elderly person fell or suffered a heart attack. "Our lab's success rests, in part, on having unique tools," Mr. Stroetz says. "If you have a better tool, you have a better understanding of the human body."

- Barbara Toman