Implantable Heart Aid

victims, however, the Automatic Implantable Cardioverter Defibrillator, or AICDTM (shown at right) offers new hope: it can reduce the two-year SCD mortality rate to less than three percent.

The AICD incorporates spacebased miniaturized electronics to detect a broad range of spontaneous heart arrhythmias, including those caused by ventricular fibrillation, during which the heart loses its ability to pump blood, causing death or brain damage in minutes. The AICD works by shocking the heart via electrodes that have been surgically placed in and on the heart. Comprising a pulse generator and two sensors that continuously monitor heart activity, the AICD automatically

delivers electrical countershocks to restore rhythmic heartbeat as

necessary. It works in the same way as defibrillators used

by emergency squads and hospitals, but

offers the

advantage of being permanently

available to

patients with high

risk of experi

encing SCD.

The AICD pulse generator was developed in the early 1970s by Intec Systems Inc. and Medrad Inc., Pittsburgh, PA, in conjunction with researchers at Sinai Hospital, Baltimore, Maryland.

NASA funded development of an AICD recording system and an independent design review of the system, both conducted by the Applied Physics Laboratory of Johns Hopkins University, Howard County, Maryland. The first model was successfully implanted in a dog in 1976 and, after 12 years and more than $4 million in research, the device was implanted in a 57-year-old woman at Johns Hopkins Hospital on February 4, 1980. Clinical studies ensued and a grant from NASA enabled Intec Systems and the Applied Physics Laboratory to pursue

development of more advanced models.

The AICD is manufactured by Cardiac Pacemakers, Inc., St. Paul, Minnesota, a subsidiary of Eli Lilly and Company, which purchased Intec Systems in 1985. CPI was the first company to receive FDA approval for an implantable defibrillator and continues to work to make this lifesaving technology available to a greater number of patients.

as an electronic artificial pancreas that infuses insulin at a pre-programmed rate, allowing for more precise control of blood sugar levels, without which complications such as blindness and kidney disease may result, while freeing the diabetic from the burden of daily insulin injections.

The Programmable Implantable Medication System (PIMS) resulted from efforts begun in the 1970s at NASA's Goddard Space Flight Center to transfer aerospace technology to the medical field. Created by the Applied Physics Laboratory of Johns Hopkins University in cooperation with Goddard and MiniMed Technologies, a California-based manufacturer of medical equipment, the PIMS is surgically implanted in the diabetic's abdomen to continuously deliver insulin.

The implant consists of a refillable drug reservoir, a pumping mechanism, a catheter leading from the pump to the diabetic's intestines, a microcomputer, and a lithium battery-all encased in a titanium shell 3.2 inches in diameter and threequarters of an inch thick. The pump's tiny dimensions are the product of years of work to miniaturize

cavity in short bursts or "pulses." which conserves battery power. When an insulin refill is needed-about four times a year-it can be injected without surgery by a special hypodermic needle.

Both patient and physician can adjust the insulin delivery rate via digital telemetry-a technique developed by NASA to communicate with spacecraft from Earth. By holding a small radio transmitter over the implant and dialing one of ten preprogrammed codes, the diabetic can change the infusion rate or ask for a supplemental dose of insulin before meals or when blood sugar levels are elevated. Another code allows the physician to access information from the pump's stored memory, reprogram insulin delivery, and generate computer records of the pump's performance.

A device similar to the PIMS, but worn externally, is the MiniMed® 504 Insulin Infusion Pump. Also based on NASA technology, the MiniMed 504 can be clipped to a belt or other part of the user's clothing and worn around the clock. About the size of a credit card and weighing just 3.8 ounces, it houses a microprocessor, a long-life battery, and a syringe reservoir filled with insulin. The syringe is connected to an infusion set that consists of a thin, flexible plastic tube about 30 inches long with a needle at its end. The patient inserts the needle subcutaneously, usually in the abdomen. Insulin is infused at rates determined by the patient's needs and programmed into the microprocessor.

under the trade name CorTemp by

Human Technologies, Inc. of St.

Petersburg, Florida) enables improved patient care in hospitals and offers opportunities in medical experimentation.

The three-quarter-inch silicone capsule contains a telemetry system, a microbattery, and a quartz crystal temperature sensor. The sensor reads the internal temperature and telemeters the information to a receiving coil outside the body. From

there it is relayed to a computer. The ITMS monitors continuously during the 24 to 78 hours it takes the capsule to travel through the digestive system.

The pill can record a patient's temperature every 30 seconds and can be programmed to sound an alarm if the temperature exceeds preset limits.

Researchers developed the ITMS for treatment of such emergency conditions as dangerously low (hypothermia) and dangerously high (hyperthermia) body temperatures. Extremely accurate readings are vital in treating such cases. While the average thermometer is accurate to one-tenth of a degree Centigrade, ITMS is off no more than one hundredth of a degree, and provides

the only means of gauging deep body temperature.

Although the concept for the temperature pill dates back to the 1950s, until recently technology could not produce parts small enough for an ingestible capsule, while meeting reliability, accuracy, and cost objectives. The ITMS achieves these performance goals by adopting spacebased technologies such as miniaturized integrated circuits and telemetry techniques originally developed for transmission of coded signals to Earth from orbiting satellites. The system has applications in fertility

monitoring,

incubator

monitoring, and some aspects of surgery, critical care, obstetrics, metabolic disease treatment, gerontology (aging), and food processing

research. APL is working on an

advanced fourchannel capsule

that will simultaneously monitor

temperature,

heart rate, inner body pressure, and acidity.

The technique could save considerable time for nurses, who take many temperatures in the course of a hospital shift. In the U.S. alone, some two billion clinical temperature readings are taken annually, about half of them in acute care hospital facilities. The national shortage of nursing personnel spurred Diatek to pursue development of a faster thermometer. The company's researchers turned to infrared optical technology because it offered quick operation and extreme accuracy. The Model 7000 optical sensor was designed by Diatek engineers and refined with help from NASA's Jet Propulsion Laboratory, which has 30

years experience using infrared sensors to remotely measure the temperatures of planets and stars.

To take a temperature, the nurse inserts the plastic-covered probe into the opening of the patient's ear canal and presses a button to activate the sensor. The probe detects infrared radiation emitted from the eardrum and a microprocessor converts it to the corresponding body temperature, which is displayed on a liquid crystal screen. The aural device enhances the comfort of critically ill, incapacitated, or newborn patients, and makes frequent temperature taking less bothersome. Further, it reduces the risk of cross-infection because it avoids contact with mucous membranes and employs disposable probe covers.

The thermometer weighs only eight ounces and can be operated with one hand. It is targeted for acutecare hospitals and alternative health

care sites such as nursing homes, blood banks, and cancer and burn centers. Diatek expects 60 percent of all clinical thermometers to use infrared sensors by 1997.

A nurse takes a patient's temperature with the Diatek Model 7000 aural thermometer, which employs infrared technology to obtain a nearinstantaneous reading.

Thermal Video

Health and Medicine

disease. A

localized hot spot on the skin's

surface might indicate unseen inflammation, while a cold spot could be symptomatic of poor blood circulation. In the past, however, there was no way to accurately measure fluctuating heat emissions. Now, through the rapidly advancing technology of infrared thermography, physicians have a tool to detect the slight temperature differences that warn of pathology.

Thermographic devices convert invisible infrared (IR) radiation into voltage signals that can be displayed on a monitor. The first IR sensors were developed for military purposes such as missile guidance. Hughes Aircraft Company pioneered the civil application of IR heat sensors as part of a NASA-sponsored research project. More recently, medical use of thermography has rapidly gained acceptance as a noninvasive means of observing physiological problems. Whereas an x-ray indicates structural anomalies, thermography can point out functional anomalies. For instance, a thermogram showing an

asymmetrical temperature pattern on the body surface serves as a visual indicator of pain, while mapping of dermatones (areas of skin supplied by a specific spinal nerve) enables accurate measurement of nerve dysfunction. Sensory nerve

impairment in the lower back is indicated by a temperature difference, from one extremity to the other, of only 1° C.

Thermography is proving to be a valuable screening tool in diagnosis. It can provide information that obviates the need to do more invasive tests that might be painful or hazardous. Thermal imaging also can verify a patient's progress through therapy and rehabilitation, and it is finding special utility in determining the extent of sports injuries.

This thermographic image reveals that the first two fingers of the right hand emit less heat at the skin

surface, indicating subnormal blood circulation.

One of the leading purveyors of thermographic equipment is FLIR Systems of Portland, Oregon. The company purchased Hughes' line of Probeye thermal video systems in 1990 and now markets a wide range of infrared systems and accessories, principally for industrial uses such as inspection of electronic components, profiling for nondestructive testing, quality inspection, preventive maintenance, and routine monitoring of production processes and energy losses.