Device for Controlling Stimulus Self-Application During Autonomic Nervous System Tests

Figure 1. Example of incorrectly (693 −709 s) and correctly (732 −748 s) performed Valsalva maneuvers and resulting heart rate and arterial pressure responses. During the incorrectly performed maneuver, a 70-year-old man was maintaining correct mouth air pressure except for a short period, when this pressure dropped to 0. During correctly performed maneuver, the mouth air pressure was maintained throughout the test. Heart rate rise and arterial pressure drop were lower during the incorrectly performed maneuver in comparison to the correctly performed one, rendering incorrect assessment of magnitude of ANS reaction.

Figure 2. Information needed to perform the test correctly is shown on the LED display, in the same way during different ANS tests. The most important advantage of such a solution is that the subject is confronted with the same way of conveying information from measuring device trying to get the desired level of different stimuli or pattern of activity which is conceptualized in the same way. This removes the need to familiarize a subject with different measuring devices used in various ANS tests and to teach them about how the desired goal is presented in particular measuring devices.

Figure 3. Block diagram of the device. Device consists of two measurement channels: one connected to the built-in pressure sensor and another one connected to the external sensor (dynamometer). The microcontroller converts an analog signal to visual information, ie, the position of turned-on LEDs on the display. The USB interface is used to communicate with a computer. The device can operate as a metronome, air pressure or force display.

Figure 4. Electronic scheme of one LED display module (one of 5 similar in modules in the whole display). To turn LED on, for instance LED1 in module no. 1, pin 1 must be set high and A low, B–E pins must be set high, so using 10 pins, divided in two 5 pin sets, ie, (1−5) and (A–B) the device can control 25 (ie, 52) LEDs.

Figure 5. Calibration line of pressure measurement. Voltage output is calibrated using pressure measured with mercury sphygmomanometer.