Plan your study

The following questions will help you plan your ZMax study.

How many electrodes will you need?

ZMax uses disposable gel electrode patches. These can be reused several times. For most studies up to 7 nights per patient, you will likely want one electrode patch per patient. Though there is no substantial degradation in signal quality with multiple uses, the electrode patch will suffer cosmetic degradation the longer it's used. So you may still want to have a new electrode for each night.

What size electrodes will you need?

We have two electrode sizes, for children and adults, so do let us know which size you prefer when placing an order. In some cases female patients should use the children size electrodes. You can determine this by placing a regular size electrode on the patient's forehead. If the 'arms' of the electrode patch are too long some hair will get trapped between the skin and the gel pads below the electrode patch. This is to be avoided. If you only have an adult size electrode and wish to shorten it, you can fold it without deterioration in the acquired signal provided that you take care of preventing electrode disconnections. Disconnections may be more likely when the electrode is folded. In case of doubt and for important recordings, you can always tape a folded electrode in place.

Will you need to record multiple patients simultaneously?

Here we get into data transmission spanning both wireless and network. The possibilities may seem a bit daunting because ZMax offers so many possibilities for signal acquisition. If you wish, you can skip all of this and simply e-mail us to schedule a telephone or skype appointment, during which we will guide you through this step by step and recommend the best way to acquire data for your study.

Currently ZMax does not support simultaneous acquisition from multiple devices using wireless transmission. Devices send data at the same frequency and will interfere with one another is used in the same physical location. Furthermore one server instance is not capable of using multiple USB receivers to receive multiple radio transmission streams. This is not a limitation with the hardware but only with the software. If demand exists, we may offer concurrent wireless recording as an upgrade in the future.

If you wish to record one patient and one night at a time, this does not apply to you and there is no decision to be made.

If you wish to speed up your study by acquiring different participants at a time you have the following options:

All patients are remote. Wireless recording

If all patients are remote you have isolated recording environments. You do not need to worry about wireless transmission. You simply need multiple instances of HDRecorder. Multiple instances can run on the same machine (each time you open the program it will open a new instance). Each instance will connect to a different remote IP address. There is no other particular concern.

* Requires the server to run at the patient's location

All patients are remote. Memory card storage

Patients can be instructed on how to acquire data autonomously on the memory card. Alternatively, HDRecorder can be used to "dial in" and check the signal, and the remote technician can initiate memory card storage remotely on behalf of the patient.

* Remote signal checking requires the server to run at the patient's location

All patients are local. Staggered recording on memory cards

Multiple patients sleep at the same time in the same physical environment. Data is stored on the internal memory card. Prior to each patient going to sleep, the technician can optionally preview the signal wirelessly to ensure that the device is properly worn. As an example, first, patient 1 would wear the device, the technician would monitor the signal wirelessly, and when satisfied with the quality, would initiate memory card storage. Then, patient 2 would wear a second device. At this point only device 2 would be sending data. The technician would monitor the signal from patient 2 wirelessly, and when satisfied would initiate memory card storage. And so on.

All patients are local. Simultaneous wireless recording in isolated rooms

If you can place each transmitter/receiver pair sufficiently far apart, you may use wireless recording throughout the night. However, you need to ensure that there is no 'data leakage'. To do this you would initiate wireless transmission from patient 1 in room 1, then move to room 2 and start a new server with a second USB receiver. You would monitor the 'packet count' (a mesure of how much data is received) to ensure that it remains at zero regardless of patient 1's sleeping position. If it does remain at zero, the broadcast power is not sufficient to reach room 2, therefore you have two isolated recording environments and have no particular concerns. Do make sure that as patient 1's sleeping position varies, server 2 does not begin to receive data. Even just 1 or 2 packets will corrupt the timebase of the recording.

If you have multiple local isolated environments, it is convenient to set up a server in each environment, and monitor all the patients from a single PC. This works identically to the process described in "All patients are remote. Wireless recording" except that you are dialing LAN IP addresses as opposed to global IP addresses. Obviously each PC must be connected to the same LAN/router.

Please see the Connectivity section for more information on network connections. More exhaustive information on establishing connections is available on our Windows format CHM manual available under downloads. It is recommended for the technicians/researchers to experiment using ZMax to record data wirelessly for the first few nights. This way the technician is able to learn how to properly fasten the headband.

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