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Upgrade Your HRV Biofeedback System

Updated: Jun 17



Professionals can deliver effective HRV biofeedback training using consumer-grade equipment that does not monitor EMG or breathing. For example, the Institute of HeartMath's emWave Pro Plus ($499) and Inner Balance ($249), and Optimal HRV's HRV Reader ($49.99) represent sound engineering and excellent values.

Pro Plus

Inner Balance
HR Reader


Why Should You Monitor Breathing?

Slow-paced breathing, a core element of many HRV biofeedback protocols, can be challenging for many clients since they often breathe two or three times faster (Meehan & Shaffer, 2024). Identifying and correcting dysfunctional breathing patterns can increase your client's success and motivation. If you don’t correct dysfunctional breathing patterns like overbreathing, they can compromise the effectiveness of HRVB training.


Overbreathing is a mismatch between breathing rate and depth (Khazan, 2019). This disparity may involve rapid breathing, increased tidal volume (air exhaled during a breath), and more subtle behaviors like gasps and sighs. Graphic © Silvia Bukovac/


When clients expel excessive CO2, this lowers end-tidal CO2 (the percentage of CO2 at the end of exhalation) and causes hypocapnia, which is deficient CO2. Healthy end-tidal CO2 values range from 35-45 mmHg. Moderate overbreathing can reduce oxygen delivery to the brain by 30%-40%, and severe overbreathing can reduce it by 60%.

ETCO2 table

Overbreathing can produce acute and chronic vasoconstriction effects and reduced delivery of oxygen and glucose to body tissues, especially the brain (Khazan, 2013).

The SPECT scan created by Scott Woods below shows the effect of overbreathing on brain metabolism. Darker colors represent reduced metabolism and compromised cortical functioning.


What can a breathing sensor contribute to HRV biofeedback training?

During assessment, a respirometer (flexible breathing sensor) can measure breathing rate and depth but not end-tidal CO2. These readings can guide breathing training before starting HRV biofeedback. Your client can use a respirometer display to gradually slow their breathing toward their training goal. Graphic © Association for Applied Psychophysiology and Biofeedback.

A respirometer can warn when your client tries too hard, such as taking typical deep breaths.

Real Genius

Respiration rate (RR) and abdominal amplitude (violet) may increase during effortful breathing. EMG activity (red) may increase if you monitor breathing accessory muscles like the scalenes and trapezius.

The breathing waveform may become jagged instead of sinusoidal.

effortful breathing

Caption: There are three inflection points in the screen capture below (marked by yellow arrows) where the second breathing cycle is distorted by effort.

The instantaneous heart rate (HR) and breathing waveforms may be out of phase, causing the peaks and valleys not to align.

BCIA HRV Biofeedback Certification

Professionals pursuing BCIA HRV Biofeedback Certification must complete 20 patient/client treatment sessions using HRV biofeedback, including PPG or ECG training and respirometer training. BCIA's Essential Skills include BVP, ECG, EMG, and respirometer expertise, and artifacting. Your staff cannot satisfy these requirements with products limited to ECG or PPG sensors.

Physiocom Design Offers Affordable Professional-Grade Systems

Physiocom Design succeeds J & J Engineering, one of the most respected manufacturers in the field. Jan Hoover, pictured below, continues to helm his company.

Jan Hoover

For orders, you may contact them at (360) 216-7468 from Tuesday through Thursday, 2 to 6 p.m. PST. Support is Their competitive pricing allows clinics to upgrade to expandable biofeedback systems. For example, their $550 GP-8e+ Physioamp monitors six channels and includes software for Windows 10 and 11.


Two channels are reserved for ECG, EEG, or EMG. You can select the gain and bandwidth for these signals. Two are designated for temperature, respiration, or other high-level sensors. Finally, one is assigned for skin resistance and one for PPG to measure HR, HRV, and blood volume pulse (BVP).

Their $110 GP-5u Respiration Sensor Belt converts stretch to a respiration waveform, and their $70 OS-2p PPG Finger Sensor monitors HR, HRV, and BVP.


Physiocom Design has also released an affordable capnometer measuring end-tidal CO2 (ETCO2). Since ETCO2 often declines with effort, a capnometer can show whether values fall below 36 mmHg. See the segment from 01:40 to 03:20. Graphic © Inna Khazan.


Their $1750 GA-1 CO2 Analyzer comes with dedicated software or can use GP-8e+ software.


data display


Physiocom Design has made upgrading your clinic's HRV biofeedback system very affordable. You can monitor HR and HRV using a finger PPG or wrist ECG sensor. Adding a respirometer can enhance HRV assessment and training. Experienced clinicians and researchers can use a capnometer for "gold standard" breathing assessment and training. We encourage you to assign home HRV practice using products like the Institute of Heartmath's Inner Balance and the Optimal HRV application. These products are intuitive and motivating, aid in assessing progress outside the clinic, and promote generalization from the clinic to your client's everyday life.


BioSource Software does not accept advertising and has no commercial relationship with Physiocom Design. Dr. Fred Shaffer, BioSource Software's CEO, does not consult for a fee to avoid conflicts of interest.


capnometer: an instrument that monitors the carbon dioxide (CO2) concentration in an air sample (end-tidal CO2) by measuring the absorption of infrared light.

end-tidal CO2: the percentage of CO2 in exhaled air at the end of exhalation.

overbreathing: subtle breathing behaviors like sighs and yawns reduce end-tidal CO2 below 5%, exceeding the body's need to eliminate CO2.

photoplethysmographic (PPG) sensor: a photoelectric transducer that transmits and detects infrared light that passes through or is reflected off tissue to measure brief changes in blood volume and detect the pulse wave.

pulse oximeter: a device that measures dissolved oxygen in the bloodstream using a photoplethysmograph sensor placed against a finger or earlobe.

resonance frequency: the frequency at which a system, like the cardiovascular system, can be activated or stimulated.

respirometer: a sensor that changes resistance to a current as it expands and contracts during the respiratory cycle.


Khazan, I. Z. (2013). The clinical handbook of biofeedback: A step-by-step guide for training and practice with mindfulness. John Wiley & Sons, Ltd.

Khazan, I. (2019). Biofeedback and mindfulness in everyday life: Practical solutions for improving your health and performance. W. W. Norton & Company.

Meehan, Z. M., & Shaffer, F. (2024). Do Longer Exhalations Increase HRV During Slow-Paced Breathing? Applied Psychophysiology and Biofeedback, 10.1007/s10484-024-09637-2. Advance online publication.

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