The SB-1 EKG Blanker
is a unique instrument for reducing the cardiac artifact in respiratory muscle recordings
, especially the diaphragm EMG. Its many advanced features make it easy to set up and operate.
The instrument accepts an amplified EMG signal as its input and, optionally, an amplified EKG signal. Outputs include a standardized-amplitude version of the input signal (amp out), a processed and full-wave rectified signal (out), and a sync out logic signal corresponding to the EKG R-wave.
The artifact reduction technique employs a time delay circuit whereby the signal is digitized and delayed out of real time by a short period (approximately 50mS). The internal software triggers from the embedded artifact in the real-time signal (or from the external EKG input), and predictively processes the delayed signal.
Setting up the instrument is straightforward. In auto setup mode, the signal gains are automatically standardized, and the blanking process optimized. The various blanking parameters can also be manually set if desired. Heart rate and respiratory rate are computed and displayed on the LCD. An audible EKG beep can be turned on or off as desired.
The rectified output of the SB-1 is generally fed to a Moving Averager
, which produces a smoothed envelope around the EMG activity.
Although designed for human diaphragm EMG processing, the wide measurement range of the SB-1 makes it suitable for use with other muscles and a variety of experimental animals
Sample SB-1 tracing with simulated diaphragm EMG.
Top: amplified raw signal
Middle: rectified raw signal
Bottom: blanked output signal
(norm mode at right, null mode at left)