It is astounding to compare the medical technology of today with that of 1900. Then, doctors with small black bags came to one's house and, using a few instruments and their senses, determined one's illness. A trip to a doctor's office or hospital would not find much more in the area of diagnostic tools. The X-ray machine had just been invented.

Today, people live nearly 30 years longer, on the average, than their great-grandparents did at the beginning of the 20th century. Many factors in public health and medical discoveries contributed to this, but in no other area since the Industrial Revolution has engineering started from so limited a base and produced such an invaluable, complex, and startling number of innovations. Although many advances were underway early in the century, health technologies really began to blossom in the last half, when engineering and medicine became increasingly interdisciplinary, and the human body was more fully recognized as a complex system of electrical fields, fluid and biomechanics, chemistry, and motion - ideal for an engineering approach to many of its problems. There are currently some 32,000 bioengineers working in various areas of health technology.

Since then, engineers have worked with the medical profession to develop artificial organs, replacement joints, life-enhancing systems, diagnostic and imaging technologies -- remarkable machines, materials, and devices that save lives and significantly improve the quality of life for millions. The technologies for surgery, medical implants, bioimaging, and intensive care units, as well as methods to mass-produce antibiotics and other drugs, are all a vital part of this story.

Each year, worldwide, physicians implant 200,000 pacemakers, 100,000 heart valves, 1 million orthopedic devices, and 5 million intraocular lenses. A number of machines make many of these surgeries possible. The heart-lung machine mechanically pumps and maintains a patient's blood circulation and pulmonary function during heart and lung transplant surgery by shunting blood away from the heart, oxygenating it, and returning it to the body. The blood-heat exchanger safely and quickly lowers and raises a patient's body temperature before and after surgery. Before its invention, this process took hours, which meant more risks to the patient, including a longer period of time under anesthesia. The kidney dialysis machine is a pumping and filtering system of tubing, compressed air, dialysate and coiled membrane tanks that purify blood in patients suffering from kidney failure. It has helped millions of people suffering from kidney disease, and is currently keeping an estimated 55,000 people with end-stage renal disease alive, many of whom will eventually receive kidney transplants.

Artificial hearts are engineered to replicate the heart's pumping function and keep patients alive until suitable donors can be found. Mechanical or electromechanical devices such as pacemakers and defibrillators regulate heartbeats and correct rhythm dysfunction. Damaged valves are routinely replaced with prosthetics. Ventricular assist devices can provide circulatory support by assuming the work of the failed heart, allowing the organ to recover normal functions.

The modern pharmaceutical industry introduced highly active medicinal compounds in the 19th century and life-saving sulfa drugs and vaccines in the 20th. But without two major engineering components, these discoveries would have meant little to the masses: the fermentation process through which many pharmaceuticals are grown, and the large-scale manufacturing techniques that mix, shape, package and deliver drugs in all their forms, from millions of vials and pills to gallons of serum and liquids. These medicines greatly reduced or completely eradicated diseases that plagued the population for much of this century, such as rheumatic and typhoid fever, lobar pneumonia, poliomyelitis, syphilis, and tuberculosis.

Pharmaceuticals have also provided greater protection from infection, which has allowed doctors to go farther in repairing and replacing damaged or worn-out tissues with engineered materials (biomaterials). Synthetic and biological polymers, metals, and ceramics, are used for almost everything from suture material to heart valves, and to replace bones or eye lenses. Inert metals, such as vitallium, are used to repair fractures or replace joints. Silicone capsules protect implanted electric equipment, such as cardiac pacemakers. Woven acrylic artificial arteries prevent rapid clotting of blood in artificial blood vessels. With such a tremendous increase in medical applications, demand for new biomaterials grows by 5 to 15 percent each year.

Some of the very latest technologies are prevalent in the operating room. The medical laser, first developed for use in eye surgery in the 1960s, can vaporize brain tumors via selective wavelengths without harming surrounding tissue, "weld" nerves and blood vessels in transplant surgery, and act as a "bloodless scalpel" to perform many types of surgery with little or no blood loss. The operating microscope has expanded the scope of surgery through the benefit of magnification — critical in neurosurgery. By using liquid nitrogen, cryosurgery can destroy cancerous tumors.

With the invention of the transistor in 1948, microelectronics altered the size and quality of many medical devices, like the hearing aid. It also made some bulky mainframe-dependent systems portable for home use, most poignantly seen in crib alarm systems for infants susceptible to sudden infant death syndrome. The intensive care unit is a technological wonder, replete with microelectronic systems, as is the incubator, which engineers transformed from a simple warming device for premature infants to a complex life-support system.

Computer-aided design and manufacture help to ensure the best fit for prosthetic limbs. Techniques include digitized plaster impressions, optical shape sensors that rotate about the limb to collect data points, and laser shape sensing. The computer has also advanced research in myoelectrics, which will help power prosthetic limbs through a combination of muscle contractions and electrodes.

The impact of engineering in the medical arena and the resulting benefits to the average person are incalculable. In no other field have engineers become so intimately wedded to life itself.