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Q: How often do you recommend calibrating the AIM-8 monitor?  And how is the AIM calibrated?

A: We recommend calibrating the AIM-8 monitor about once a week if it is being used on a regular basis, although, it seems to hold it's calibration setup for months. In fact, we have checked some units that have not been re-calibrated for six months, and found their calibration information to still be correct for the current conditions. However, it certainly doesn't hurt anything to re-calibrate before each measurement session. A good clue as to when the AIM-8 needs to be calibrated is obtained by using the SCOPE mode while the AIM-8 is connected to the AIM Calibration Box, and with electrode lead #5 connected (shorted) to both electrode lead #1 and the CAL box terminal #1. Under this condition, if the EKG baseline signal doesn't appear to be very close to (within a couple of millimeters), or right on top of the X-axis of the EKG scope display, then the AIM-8 probably needs to be re-calibrated. It is important to remember to always short lead #5 to lead #1 on the calibration box when calibrating the AIM-8! Otherwise, a false EKG baseline offset will be established during the calibration process with electrode lead #5 just floating in space.

Q: The AIM-8's remote Blood Pressure (BP) Sensor does not seem to be activating the AIM unit. What should I do?

A: First, it should be verified that the AIM-8's pushbutton switch can initiate an Ensemble Average (EA) properly. Then, it should be verified that both the manual pushbutton switch and the BP Sensor, activated for at least 2 seconds, will initiate an EA measurement. If the problem persists after these precautions have been made, then it should be reported to BIT, Inc.

Q: The ECG signal from the AIM-8 unit seems to become fuzzy after about 30 minutes. Why is this happening and how can it be prevented?

A: A low battery can cause the fuzzy ECG signal. When the battery voltage drops to around 5.1volts, the internal voltage regulator can generate some low level noise that can be detected by the sensitive impedance cardiography circuitry and appear in both the ECG and dZ/dt signals. Therefore, it is important to use a new, fresh, and high-capacity 9volt battery to power the AIM-8. It is also important to keep the AIM in sleep mode during the majority of the time between actual measurements. For in-lab applications, a battery eliminator may be used to power the AIM-8 monitor if the eliminator's rated output voltage is between 9volts and 1 2volts.

Q: Is it possible to get Heart Rate (HR) variability from AIM-8 data?

A: Yes. HR variability may be examined through the cardiac cycles recorded during the ensemble averages (EA's). The inter-beat-interval (IBI) data obtained by the AIM-8 is needed for this type of analysis. COPWORKS can create an IBI file containing all the IBI's for each EA measurement. These IBI's are used by the Data Scan analysis to determine cycle-by-cycle heart rate. A longer EA duration time may be needed in order for the HR variability information to be useful; however, increasing the EA duration to examine HR variability lessens the quality of Impedance Cardiography measurements, for which low HR variability is desirable.

Q: Are the AIM-8 calibration scale factors supposed to vary from one monitor to the next?

A: This depends on the amount by which they vary. When using more than one AIM-8 monitor, one may notice that the calibration scale factors may differ between the units. This variation is normal and to be expected since there are variations in the Analog to Digital converters used in each unit. However, scale factors near or above 1.0 would be way out of range, and, therefore, indicated a problem with the monitor, electrode cable, calibration box, or the AIM_HOST system. Even scale factors greater than 0.1 are too large and indicate a possible problem somewhere in the system.

Q: Which battery should be used to power the AIM-8?

A: The Energizer Titanium or the Rayovac Maximum. The Energizer Titanium 9volt battery has enough life to power the AIM-8 Monitor running in a continuous data acquisition mode for 9 to 10 hours. This means that when operating in a normal mode using 40 second EA duration times, for example, and sleeping between these EA measurements, the AIM-8 monitor can obtain 100 measurements and still have enough power to stay in the sleep mode for 120 days.

Q: I have an AIM-8 Impedance monitor and AIM_HOST software system. Is there a laboratory model that has software as user friendly as AIM_HOST and COPWORKS?

A: Yes. The COP_WIN 5.05 system is a laboratory version which is compatible with the Minnesota Cardiograph 304B (no longer in production) or the new HIC-2000 Impedance Cardiograph. The HIC-2000 is available from Instrumentation for Medicine, Inc. (IFM), and the COP_WIN 5.05 system is available from Bio-Impedance Technology, Inc. (BIT).

Q: The AIM system's RS-232 communication cable is too short. How can I get a longer one?

A: The easiest and cheapest solution would be to purchase an extension cable from RadioShack with a 1/8" stereo phone plug on one end and a 1/8" stereo phone jack on the other end. (Note: see question below for additional information.)

Q: Can the AIM-8 monitor work with a RS-232 serial communication cable lengthened from 60' to 100'?

A: Yes, the serial data communication cable will work with a 60' to 100' cable extension. This longer cable will add capacitance that could attenuate the communication signal, but the system should still work with the extended cable.

Q: Can the AIM-8 be used in a hyper baric chamber?

A: The AIM-8 has never been tested in a hyper baric chamber. The effects of such conditions on the AIM-8 unit are, therefore, unknown.

Q: Are there any non-solid components such as electrolytic capacitors in the AIM-8 unit?

A: No. There are no non-solid electronic components used in the AIM.

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