Telemetering from within the body using a pressure-sensitive radio pill

It has been an aim of the clinical physiologist to be able to measure continuously such physiological variables as pressure, temperature, and hydrogen ion concentration under conditions of minimal disturbance to the subject or his environment.The development of miniature electronic components, such as the transistor, has made it possible to construct transducers and amplifiers within such a small space that studies can be undertaken in hitherto inaccessible parts of the human body.A radio transmitter with a total volume of approximately 2 cc.which can transmit information from the inside of the body was described in 1957 (Mackay and Jacobson, 1957).These devices have been further developed and they have been used mainly to investigate the gastrointestinal tract.Telemetering capsules ('radio pills') capable of recording pressure, temperature, and pH have been produced and a review of these devices is given elsewhere (Mackay, 1959(Mackay, , 1961;;Jacobson, 1960;Wolff, 1961).They transmit a frequency modulated signal in the frequency range 300 Kc/s to 10 Mc/s.The pressure pill modifications described in this paper enable the construction of a simple, reliable and inexpensive device.SPECIFICATION 1 The device should be as small as possible and not greater than 3 cm.long by 1 cm.diameter.