A computer-controlled cardiotachometer

Abstract

A versatile display system for presenting heart rate information is described. The display has a table with 10 rows and 50 columns. This 10 by 50 matrix contains all integers from o to 499, so that it can display the instantaneous R•R intervals of a rat's EKG to the nearest millisecond. At each beat 1 of 10 vertically and 1 of 50 horizontally arranged indicator lights are turned on to provide the coordinates for reading the table. Either beat-to-beat or averaged heart rate or period is displayed. Small and large changes can be easily and accurately observed on the same scale. The lights are controlled by a PDP-8/e. A listing of the assembler program is presented. In a large number of psychophysiological investigations involving measurement of heart rate (HR), an immediate indication of ongoing HR behavior is essential or at least helpful (e.g., studies of biofeedback, stress, habituation, or classical conditioning). TYPES OF CARDIOTACHOMETERS Several different cardiotachometers are available. The design of these units is usually based on analog circuitry that provides a voltage proportional to the reciprocal of the time interval between successive R waves. HR is indicated by a needle or pen that points to a scale (voltmeter type) or writes "staircases" on recording paper (tachograph) (e.g., Pope, Deboo, & Smith, 1968). Readings from these instruments are far from being exact. Digital tachometers are highly accurate (e.g., Elings & Holly, 1973), but the dynamics of HR changes are poorly represented by numbers, and watching beat-tobeat changes in HR over a longer period of time on a LED display is a tedious job that absorbs most of the experimenter's attention. Computers have been used successfully for the interpretation of the EKG complex (e.g., Wartak, Milliken, & Karchmar, 1970), but they have contributed little to improving HR monitoring. A computer-controlled cardiotachometer (CCC) that is accurate, easily readable, and versatile is described here. COMPUTER-CONTROLLED CARDIOTACHOMETER Display The CCC's display has an interchangeable table of HR or heart period values. Ten vertically and 50 hori-Development of this system was supported in part by Grant Li 74/10 from the Deutsche Forschungsgemeinschaft to Gustav A_ Lienert. Requests for reprints should be addressed to Wolfl/;ang Klosterhalfen,

Habituation of heart rate in functionally decorticate rats.

“…A PDP/8 computer used a PAL/8 program to analyze the ECG, to control a cardiotachometer (Klosterhalfen, 1980), and to calculate heart rate (HR) on the basis of averaged R-R intervals: R waves produced Schmitt trigger interrupts which were accepted for calculating beats per minute only when they occurred at intervals of more than 100 and less than 250 ms and when they did not occur at the onset of the acoustical stimuli, the time at which most of the rare movement artifacts were observed.…”