Knowledge Base

Analyze Heart Rate, Heart Rate Variability And Breathing Rate

Aim

To switch on heart rate, heart rate variability, and breathing rate analysis.

Prerequisite

You have the Vital Signs Module.

Procedure

1. Choose File > Settings > Analysis options.
2. Under Optional Classifications, select Vital signs.

Note

The option to analyze vital signs must be switched on, which is by default the case if you have the Vital Signs Module. However, when you upgrade a basic FaceReader license with the Vital Signs Module, you must switch the option on manually.

Analysis In Phases

Heart rate and breathing rate analysis is carried out in three phases, calibration, calculation, and post-processing.

Calibration

FaceReader requires a 8.5 second calibration period for RPPG measurements in which the signal of the skin color is sampled and processed for a reliable measurement. During the calibration stage the test participant should look into the camera and avoid extensive head movement.

Calibration is done at the start of analysis and every time the participant's face is found again after it was not found for some time. When the face is found again, the Heart rate window shows Calibrating.

FaceReader needs at least 5 minutes to calculate a value for the heart rate variability. This default setting was chosen according to standards found in the literature. You can change the heart rate variability period in the settings (File > Settings > Advanced settings).

The calibration period for breathing rate measurements is 15 seconds. Excessive movements of e.g., arms in front of the chest will reset calibration. If chest movements are very shallow, or there is no breathing detected, a warning message will be shown in the Vital Signs window.

Calculation

To calculate the heart rate and breathing rate, for each time step the pulses/breaths over the previous ten seconds are used. Heart rate is expressed in beats per minute (bpm) and breathing rate in breaths per minute (bpm).

Post-Processing

At the end of analysis, the estimated heart rate, heart rate variability, and breathing rate are post-processed to improve the accuracy, also in the initial 8.5/15 seconds and every time a new calibration was carried out. Note that after analysis the reported heart rate and breathing rate values can differ from those seen during analysis. Do not rely on the exact values you see during analysis.

Source: FaceReader 10 Reference Manual (Help), Noldus Information Technology