This document explains two features available in Noxturnal; Signal Grid and Event Grid, the difference between the two, where to find it and how to work with the grids. These tools offer the user availability to export signal data from Noxturnal for further processing in Excel or Matlab for example. Various mathematical functions can be applied to the signal to access the desired signal properties.
Signal Grid
Opening a Signal Grid
Open Noxturnal and open your recording in the Recording Library:
In the upper left corner, choose Add Sheet and then Empty Signal Grid:
An Empty Signal Grid Sheet will open up:
Adding Columns:
In order to add a new column to the Signal Grid sheet → Go to Add Column:
Here you can choose Signal..., Events..., Formula..., Sleep Scoring, Bouts..., Epoch Number and Time Stamp columns.
Time Stamp Column:
If you want to specify the epoch duration for this signal grid (different from the default one that is already specified for the recording), go to Add Column → Time Stamp
Here you can specify the epoch duration (ranging from 10s to 1 hour). The epoch duration defined here is then applied to all columns you create in the signal grid (note that this applies only for this particular signal grid).
Signal Column:
To add a new Signal Column, go to Add Column → Signal
Select the input signal, e.g. ECG:
Click Next >
Select the derived signal type:
Note that the signals in the signal grid are all epoch based - derived signals. The Epoch duration will display the length of the default epoch in the recording or the length of the timestamp (if defined).
Here you can choose for example the mean value of the ECG signal for every 30s:
The data is then displayed as a column.
Event Column:
To add a new event column, go again to Add Column in the upper left corner and choose Events. The following dialog appears:
Here you can choose the event types and filter for that event type. There are four filtering settings to choose from:
- Overlaps interval (as is displayed in the image above),
- Ends in interval
- Starts in interval
- Lies within interval
If you choose for example “Overlaps interval” (as has been selected in the snapshot above), you can see from the descriptive picture in the dialog that an event beginning outside the interval but extending into the interval is counted in this interval. As well as an event that starts inside the interval boundaries but extends outside the interval counted.
Note that the word Interval is used here, it is not different from the epoch but it can be either the default epoch duration (defined in settings) or, if you have specified the epoch duration specifically for this signal grid (Timestamp), it is that defined epoch duration.
When you have chosen the event and filtering, click Next >
here you can choose the display value for sample epoch. Then click Finish.
The signal grid is a real time data display, that is, if you for example score a new event in the respiratory sheet it will automatically be added to the signal grid.
Formula Column:
To add a new formula column, go to Add Column in the upper left corner and select Formula
The following dialog will open:
Here you can create formulas from the data in the signal grid. The results are displayed in each column. Look into properties for each column (double click on the column header) to see which column names represent what signal/event.
When the signal grid is exported the values in the formula column are exported but not the formula behind.
More available columns:
- Sleep scoring: Give information about sleep stages scored in each epoch
- Bouts...: Can be used to join aligned sleep scoring events into a single event for analysing. Is explained better in Event Grid section
- Epoch Number: Will display the epoch number for the corresponding data row
Column Properties:
You can double click on the column header to open the properties dialog:
In this dialog, you can edit the name and label of the signal column:
Press Apply to apply the changes but still keep the dialog open. Click OK when you are done, changes will then be applied and the dialog will close.
In the properties dialog you can customise changes such as text alignment, text color etc. You can choose the number format, significant digits and display scale.
Event Grid
Overview:
The event grid works similarly to the signal grid except for the interval definition used for analysis. Instead of using a standard epoch length defined by the epoch length of the recording or by the timestamp, the event grid is defined by an event length. Other functions should be the same as in the signal grid and will therefore not be explained in detail here.
Opening an Event Grid
To add a new Event column, go to the upper left corner, choose Add Sheet and then Empty Event Grid
An Empty Event Grid will open up.
Select Event or Bout:
Similar to the signal grid it is important to start by defining the time periods used for analysis. In this case it depends on selecting events or bouts. Click the red box as shown below
That will give the user a selection on choosing between events or bouts.
As described in the picture, the events are used to define the areas of interest. So the user should choose specific events if they want to analyse what is happening during those specific events.
Selecting bouts will take all adjacent sleep stages of the same type and merge them into a single event that can be used as periods for analysing signals and events during the various sleep stages.
Other functions available for the event grids are:
- Label: Writes out events selected. Distinguishes between event types or bouts if more than one is selected.
- Duration: Length of the event
- Start/End Time: For the selected events/bouts
- Start/End Epoch#: Defines the start and end epoch from the event
Exporting Data (applies for both signal and event grid):
Finally you have the availability to export the data from both signal and the event grid:
To export the data, click the Export column:
You have a lot of exportation options. You can export to Excel (note 250 column limit), text files, .cvs……..
We hope this article was helpful.
For further questions or concerns please contact us at support@noxmedical.com
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