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radio pill advantages and disadvantages
A capsule containing a miniature radio transmitter that can be swallowed by a patient. During its passage through the digestive tract it transmits information about internal conditions (acidity, etc.) that can be monitored by means of a radio receiver near the patient. Such capsules can contain video cameras and light sources to examine the bowel.
New sophisticated radio-telemetry capsules based on a 30-year-old technology have been specifically developed for clinical use, but their applications have the potential to reach beyond the hospital into basic research laboratories.
The ‘radio pill’ is the name given to a device developed in 1957 by Bertil Jacobson, professor of medical electronics at the Karolinska Hospital, Stockholm. He produced a very accurate radio-telemetry capsule, transmitting at 400 KHz, to measure pressure waves in the small intestine and in patients with diarrhea. Jacobson subsequently developed a tracking system for mapping the position of the device as it passed through the body, and he also developed a capsule for measuring acidity in the stomach and small intestine.
Eventually, this work was taken up by other researchers who developed pills for measuring a wide range of variables, including pressure in the urinary bladder and body temperature. Zoologists used them for applications including tracking animals and measuring temperature inside an egg during incubation.
Unfortunately, the early devices that were made commercially were often unreliable and expensive. However, a pH pill developed by H. C. Noiler in Heidelberg, and manufactured by Telefunkken, in Ulm, West Germany, was widely used in Germany, where the pill was given with a test meal to subjects in order to monitor pH levels during digestion. It was then possible for medical researchers to study the buffering action occurring during the time food was in the stomach. Advocates claimed that this was a much more accurate way of measuring acid secretion from the stomach than the contemporary methods used in clinical practice. At that time, the test involved pumping the acid from the stomach via a tube inserted through the nose and using Histamine to induce maximum acid secretion. The procedure was stressful for patients and some scientists showed that acid was continuously lost through the pylorus and therefore the re sults were erroneous in some, if not all, patients.
But in the last 10 years, radio pills have reached a high degree of sophistication. Now pH pills with an accuracy of 0.1 pH units and a transmission life of approximately three months are available commercially. Silicon chip technology, together with improvements in the manufacture of miniature batteries, has enabled scientists to reduce the size of the radio pill while improving its accuracy and lifespan. It is also possible to switch the transmitter on and off, which conserves the battery life and, thus, extends the device’s operating life.
The receiving system, relatively inexpensive at about $1,800, is extremely simple to use since the inductive field emanating from the radio pill is received in an aerial consisting of a number of turns of wire wound around a ferrite core. The signal is received over a spherical field one meter in diameter, the signal range can be increased, at the expense of battery life, of course.
The standard range of devices manufactured by London-based Remote Control Systems includes transmitters and receivers for monitoring temperature, pressure, pH, and redox potential. The prices for these pills range from about $70 to about $320. The company manufactures telemetry equipment for use in a variety of medical, laboratory, and industrial applications.
Smallest Pill
Among Remote Control Systems’ notable achievements is the development of the smallest radio pill ever to reach commercial production. It fits inside a standard pharmaceutical capsule, and provides accurate measurement of core temperature. A high-power version of this tiny telemetry implant was used by the London Zoo to measure the temperature of a female panda without sedating her. Inductive loop systems of this type offer a wide range of possibilities in chemistry and biotechnology. In any situation where it is important to have the device moving freely through a system, perhaps floating or being carried along by the process—for example, in fermentation vessels or during cell culture—the pill can transmit a signal. Thus, for the first time the process can be followed without having a large number of probes entering a vessel and upsetting the normal environment.
The devices can be glass encapsulated and—as long as the containing vessel is not made of metal, which shields radio waves—the process can be easily monitored. If the vessel is metal, a glass window can be provided for transmission of the signal to the outside.
Simultaneous Monitoring
The radio pill’s short range of transmission, which can be a disadvantage, actually becomes advantageous if several monitoring stations are all in one room. For example, if there are 10 patients on a ward, each patient can be monitored without interference from a neighboring patient, provided the beds are at least one meter apart. Similarly, a number of laboratory animals in the same enclosure can be monitored simultaneously.
Outside the lab or clinic, the pills are also useful. When monitoring variables from a moving object, for example in studying athletes during a sporting event, or fish with a specific frequency of identification swimming close to the aerial, the signal can be picked up and recorded on a small tape recorder and the recording can then be analyzed in the laboratory. It would be feasible in factories to have a small solid-state tape recorder in each situation that requires monitoring, and the data could then be analyzed at a central station.
Robert Colson, managing director of Remote Control Systems, published a number of papers describing the clinical use of these devices before he turned his attention toward developing the instruments to commercial standards. In recent years, the pH radio pill he developed has been used extensively, both in Europe and the United States, for measuring esophageal pH in patients suffering from chest pain to test whether acid reflux in the esophagus is the cause.
These novel devices, developed specifically for clinical use, can now be exploited for exciting applications in biotechnology and in monitoring many industrial processes, since the microtechnology required to make these devices small and reliable is now available at a reasonable price.
