Pneumatics Add Life To Medical Technology

Pneumatics: For engineers, the very term conjures up images of hissing
valves and actuators pushing parts through automated factories. For decades,
however, pneumatics have quietly played another role-that of medical workhorse.

Look around any hospital and you'll see why. Most patients' rooms are equipped with compressed air hookups. Every day, doctors, nurses, and technicians attach life-giving equipment to those hookups. Pneumatic components in those environments help deliver life-giving oxygen and medicine.

Surgeons also use pneumatics. Most operating rooms have wall outlets for compressed air, oxygen, nitrous oxide, and, sometimes, nitrogen. During surgery, pneumatic ventilators aid heavily anesthetized patients to breathe. And pneumatic tools help surgeons perform exacting operations.

Twelve years ago, pneumatics also powered one of the most heralded devices in medical history-Robert Jarvik's famed artificial heart. The heart, attached to a 375-lb electro-pneumatic drive, gave medical pioneer Barney Clark 112 days of added life.

For years, patients have used pneumatic systems at home. Oxygen concentrators provide relief for individuals with chronic lung ailments. Pneumatic cuffs help push blood through limbs with weak circulation. Orthopedic devices, such as pneumatic beds and casts, help injured patients get well quicker.

Even in the factory, pneumatics play a key medical role in the production of such commodities as syringes, rubber gloves, and x-ray film. Three examples illustrate the role of pneumatics in the medical industry. They take place in the hospital, the home, and finally, in an extraordinary application in a process plant.

High-flow ventilator caters to large-animal surgery

Surgery requirements of large animals are dramatically different from those of humans. A 1,500-lb horse in pulmonary failure, for example, could require four times as much oxygen as a person in the same condition.

Yet ventilators-the machines that breathe for heavily anesthetized patients-typically are designed for human needs. "In the past, veterinarians would not do surgery on acutely ill animals in respiratory distress," notes Bob Pearson, president and chief design engineer for Mallard Medical, an Irvine, CA-based manufacturer of ventilators. "They didn't have a machine to ventilate them, so they would euthanize them."

That solution didn't sit well with owners of prized farm animals, breeding stock, show horses, and race horses. They wanted to save their valuable animals.

Pearson worked with veterinarians at Oregon State University to provide a beter solution: a ventilator for large animals. Having tested ventilators on animals ranging from rattlesnakes to Limousine Bulls, Pearson knew the needs of the application. So he and his daughter, Rachel, designed a machine that offered higher oxygen flow rates, greater oxygen absorption in the blood, more control over respiration, and greater overall safety.

The end product, known as the Rachel Model 2800 Large Animal Anesthesia Ventilator, reportedly operates at the highest peak gas flow rate of any ventilator on the market. While human ventilators typically operate at peak flows of 100 liters per minute, Mallard's large-animal version can exceed 600 liters per minute. To achieve such flows, Pearson redesigned conventional medical venturis and used two, rather than one, in his ventilator. The tandem venturis enabled the machine to achieve flow rates 50% higher than any other

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