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  4. Which values define a good starting point for the HRV add-on’s “Filter Options”?

Which values define a good starting point for the HRV add-on’s “Filter Options”?

Heart-rate variability (HRV) is an intrinsic characteristic of human physiology, being controlled by the coupled action of sympathetic and parasympathetic components of the autonomic nervous system.

This article shows you to conduct heart rate variability analysis using PLUX products.

Why do I need Filter Options?

During the HRV processing stage of the, a great set of parameters can be used to objectively evaluate HRV, most of them with a statistical nature. Due to this statistical nature, the presence of some heart rate “outliers” will affect the results dramatically and in an undesired way, like stated in some practical examples [1][2].

To avoid these types of problems, before extracting HRV parameters, the ECG signal and the resulting heart rate information needs to be filtered for removal of ectopic beats (unexpected or false-positive peak detection). 

The OpenSignal (r)evolution HRV add-on contains a configurable section dedicated to the “ectopic beats removal” task (as shown in the following figure).

Getting Started: Required Products

Using biosignalsplux hardware:

Using BITalino hardware:

Software:

Step 1: Open the OpenSignals HRV add-on

Open the OpenSignals Visualization Mode.

plux biosignals, OpenSignals, visualization mode

Open the add-on interface by clicking on the plug icon and select the HRV add-on from the selection of available add-ons at the top.

plux biosignals, OpenSignals, HRV Add-on interface

Step 2: HRV add-on & R-Peak Detection

OpenSignals (r)evolution software includes HRV processing functionalities using acquired ECG sensor data, with the evolution of R-Peak to R-Peak intervals (RR intervals) duration along with the acquisition (tachogram). To achieve this, press the PROCESS button of the HRV add-on.

plux biosignals, OpenSignals, HRV add-on & R-Peak Detection

This processes the ECG sensor data and generates the HRV add-on results, as shown below.

plux biosignals, OpenSignals, HRV add-on results

Step 3: Opening Filtering options

For this, open the FILTER OPTIONS of the HRV add-on by clicking on the downwards facing arrow button next to the FILTER OPTIONS field, as shown in the following screenshot.

plux biosignals, OpenSignals, Filtering options

A window of filtering options will open as shown in the screenshot below.

plux biosignals OpenSignals Filtering options


Step 4: Selecting Filtering Options

Generally, heart rate can vary between 40 and 200 beats per minute (BPM), which corresponds to RR intervals between 0.30s and 1.50s [3]. For this reason, it is is logical that to set the minimum expected RR interval length (MIN RR length) and the maximum expected RR interval length (MAX RR length) limits according to the expected heart rate values within this range.

Tip

If you are expecting heart rate values ranging within other specific limitations (e.g. 60 BPM and 120 BPM), set the minimum and maximum RR accordingly (0.50s and 1.00s)

With this in mind, for this example we will assume that we will expect heart rate values between these limitations before extracting HRV parameters and will all RR intervals outside the [MIN RR, MAX RR] range will be excluded. Set the MIN (s) to 0.30 and MAX (s) to 1.50 for this example.

plux biosignals, OpenSignals, Selecting Filtering Options

In relation to the second “filtering level”, it consists of a moving average, taking into consideration the average RR interval inside a sliding window with a number “Number of RR before and after” of beats inside it. The central beat will be excluded if its duration is greater or smaller than a fraction (“% WINDOW AVG. ACCEPTANCE“) of the average value.

Reasonable starting values are 20 (“Number of RR before and after“) and 20% (“%Window Avg. Acceptance“), as proposed by Mietus from the Harvard Medical School (class available here). The 20 % value is typically accepted in clinical practice.

Updated on 13 de January de 2022

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