Latest Revision 05 July 2023
This knowledge base article is intended to help users with the configuration process for ambulatory studies using the Noxturnal App.
1 Noxturnal Mobile App – Ambulatory Study Configuration
The Noxturnal Mobile App can configure Nox A1 and A1s recorders for ambulatory sleep studies. The critical steps for configuring an ambulatory recording with the Noxturnal Mobile App are the same as in Noxturnal. The user can also use the Noxturnal mobile app to review electrode impedance values (EEG and EMG channels) and perform bio-calibrations.
Depending on the user's workflow, there are two user scenarios when using the Noxturnal Mobile App for setting up an ambulatory recording.
- Set up the patient and then configure the recorder and perform Impedance Check.
- Use the Noxturnal Mobile App to support the hookup of the EEG electrodes.
Steps 2-6 and 8-10 below apply to both user scenarios.
2. Launch the Noxturnal Mobile App and turn on your Nox A1 or A1s recorder. Wait until you see your recorder listed as an available device. If the top right circle icon stops spinning, tap it again to restart device discovery. Once your recorder appears in the list, tap it to initiate a connection.
3. On the "PATIENT" screen, enter the patient information.
4. On the "CONFIG" screen, you can configure which signals will be recorded.
The following image shows the configuration window in the Noxturnal Mobile App. In this window, you can:
- Configure the recorder by selecting a recording template.
- Add or remove an oximeter.
- Enable additional bipolar sensors (GP1 channels), such as a thermistor,
- Schedule a recording or indicate that a recording should be started manually.
Note: You can create new recording types in Noxturnal. After a single recording has been configured on the A1 recorder via Noxturnal, the recording types, bio calibration templates, and sensor definitions will be available in the Noxturnal Mobile App for this particular recorder. If you modify the recording templates in Noxturnal, you will need to configure a recording via Noxturnal again for the template changes to be reflected by the Noxturnal App.
5. On the "SENSORS" screen, you can review the sensor connections and impedance values for the EEG and EMG electrodes if the patient is hooked-up. To switch between views for the EEG and the other channels, select the circle/body icon in the lower left corner.
NOTE: For the Nox A1 recorder, a minimum of the Patient Ground and two other EEG channels must be connected to the device for accurate impedance values. If the patient is not hooked up when the A1 recorder is turned on, you must run an Impedance Check to get a reliable value for the "Head EEG" field.
The quality indicators for Pressure (Nasal and Mask) and the thermistor are based on detecting respiratory flow. Sensor quality for Pressure and thermistor now reports 0% when no breathing is detected by the cannula and 100% when breathing is detected. This indicator uses a 10-second window to report 0% signal quality if the signal peak values do not exceed a threshold. The signal will report a 100% signal quality if the threshold is reached. Note the following limitations:
• When the Thermistor has been disconnected, it can take some time (seconds to tens of seconds) to report 0% signal quality as it cools down.
• If the Thermistor was stored at a different room temperature than the testing area, it will report a 100% signal quality even though it is not connected to a subject
• If the user does not breathe for >10 seconds, the Thermistor channel will report a 0% signal quality.
6. The next step is to switch to the head screen (circle icon in the lower left corner) and start the Impedance Check by pressing the "Start impedance check" button in the figure below.
The following dialogue will pop up, and you will get asked if you want to start the Impedance Check.
Note: As stated in the dialogue, the EXG signals are corrupted during the Impedance Check.
7. This step applies to the hookup of the EEG electrodes. The Impedance Check is now running, and you can start hooking up the patient with the EEG electrodes and see real-time impedance values/color indicators on your screen. For the patient hook-up, it is critical to follow the steps below:
- Connect the patient with the oximeter and other Bluetooth devices turned on – If the oximeter or other Bluetooth devices are out of range, it can cause delays in real-time impedance values. This is because the Nox A1 recorder will do repeated scans for the oximeter, inducing a significant transmission delay to all data being transmitted to the Noxturnal Mobile App, including impedance values.
- Always start the patient hookup by attaching the electrode on the patient's forehead (ground electrode) as shown below:
- You can now continue hooking up the EEG electrodes. The sensors will be reported as "Acquiring…" until at least two electrodes and the ground (forehead) connector have been connected. From that time on, the impedance values will continuously display the status of the electrode connections and allow immediate feedback on changes.
- When satisfied with the impedance values and the hookup is completed, you can perform the bio calibration on the "BIOCAL" screen. The impedance test stops automatically when moving from the impedance check window.
8. The next step is to start the recording using the Noxturnal Mobile App and perform patient bio calibration. This link provides detailed information on performing bio-calibrations with Noxturnal App.
9. Finally, you can review all recorded signals from the "TRACES" screen.
10. When you have completed the configuration, and the patient is ready for bed, disconnect the Noxturnal Mobile App from the Nox A1 recorder by pressing the icon in the upper right corner.
Performing an Impedance Check in the Noxturnal Mobile App During a Running Study
Users may like to double-check signal quality/traces during a running ambulatory recording. The Impedance Check can be initialized as described above but must be turned off after use. There are three ways to turn off the impedance check:
- Tap the "Ohm"-icon in the top bar of the Noxturnal App
- Turn off the screen by pressing the power button of the tablet (the screen will automatically turn off in 10 minutes, stopping the Impedance Check)
- Switch to a different screen
While the Impedance Check runs, an "Ohm" icon blinks in the Noxturnal App top bar. The "Ohm" icon disappears once the Impedance Check is finished.
Note: While the Impedance Check is running, the EEG signal traces are corrupted, and the period should be scored manually as invalid data.