THE HEART RATE VARIABILITY: QUANTITATIVE INDICATOR OF THE STRESS LEVEL

Unlike many other methods of detecting diseases, the analysis of heart rate variability (HRV) is the only method which can estimate the level of mental health and even to quantify it. Put simply, HRV analyses the stress level and spare capacity of the body.

HOW THE METHOD WORKS
The heart rate variability (Baevsky’s Stress Index) is determined through a pulseoximetry procedure, which is one of the five technologies of Bioscanner Wellness device. During examination a mathematical analysis of interval duration between the heart beats is performed. Any change of the body’s internal balance always reflects on a regulation of the cardiac function, so the HRV analysis is considered as a gold standard of autonomic nervous system assessment.

For data registration taking 5 minutes, the high-sensitive sensor is used. It performs 1000 measurements per 1 second, enabling to obtain the accurate values. Besides, Bioscanner makes it possible to obtain data for HRV calculation during the procedure of electrocardiography in the first standard lead. In that case the software analyses the data from the ECG electrodes fixed on legs and arms.

WHAT IT IS USED FOR
Autonomic (vegetative) nervous system regulates internal organs, endocrine glands and vessels. It functions without our awareness: for example, the heartbeat increases and stress hormones are released in response to strong emotions. When everything is all right with the autonomic regulation, the human body runs like clockwork: successfully meets attacks of bacteria and viruses, maintains high activity of the brain, recovers fast after stress situations. Short-term stress might actually be good for the body, because it “trains” the nervous system.

However, chronic, persistent stress, like severe alteration of biologic cycles (due to overtime, chronic sleep deprivation, frequently changing time zones, etc.) exhaust the nervous system and lead to the autonomic dysregulation. Severe and/or long-lasting disease and damaging exercise can also be a stress. As a result, the body can handle any stress progressively worse, protective function is weakened, functions of the most vulnerable organs are impaired. The pre-existing disease occurs. It may not be manifested by any symptoms or can have signs of chronic fatigue, vegetovascular dysfunction. In that case, HRV analysis shows the moderate decrease of normal values. The rest or active preventive measures, including health-improving procedures, can help to prevent a disease development.

If HRV parameters deviate from the normal range significantly, it probably means a psychosomatic disorder, i. e. a disease, that is caused by dysfunction of the nervous regulation mechanisms. Today many diseases are considered as psychosomatic disorders, including different skin and cardiovascular diseases, bronchial asthma and others. HRV makes it possible not only detect autonomic dysregulation, but to monitor the treatment efficacy.

STRESS, SPORTS AND NUTRITION
HRV calculation is used for the assessment of the suitability of a person to any work that is related to stress. Sports medicine professionals are particularly active in using the HRV analysis. It allows them to determine the optimal physical activity, assess the preparedness for the next training, timely detect the exhaustion, control the health state during the rehabilitation process.

Stress index is also important for dietitian’s work to select a correct diet plan. Many people comfort eat, so no diet can help them to lose excess weight. Nutritionists often use special questionnaires to assess the stress level, but such techniques are subjective and inaccurate, unlike instrumental examination. When a high level of stress is detected, it is necessary to select an individual set of exercises in order to eliminate the influence of stress on dietary habits.

PULSEOXIMETER AND MEASUREMENT OF OXYGEN SATURATION
Pulseoximeter of Bioscanner is also used as a device estimating an arterial oxygen saturation without finger stick. Analysis is performed with the use of the sensor placed on a finger, enabling fast detection of the oxygen lack (hypoxia). This state is dangerous for any organs and tissues, but especially for the brain.

Its timely detection helps to prevent a severe hypoxia. It often occurs in premature newborns and in persons with chronic pulmonary and cardiovascular diseases. Chronic oxygen lack can occur for a variety of reasons and leads to memory impairment and difficulty concentrating, decreased functioning, weakness, sleeping disorders. It also increases risk of myocardial infarction, stroke and heart arrhythmia.

COVID-19: THE NEW REALITY
Evaluation of oxygen saturation is particularly important in circumstances of COVID-19 pandemics. Decreased blood oxygenation indicates problems in lungs and indirectly reveals the new coronavirus infection in the body.

As for HRV, stress index determination can be useful in the period after COVID-19 illness, because the nervous system damage and hyperexcitability is one of its complications.

HOW THE PROCEDURE IS PERFORMED
Connect Bioscanner to a laptop or a computer to perform pulseoximetry with HRV calculation. An electric shock hazard is excluded, because the device is supplied by USB port. Measurements are performed in a contactless way by determining the optical absorbance of the capillary blood components in red and infrared ranges.

The sensor is placed on the left or right index finger in such a way as to put a red line emitting diode (inside the sensor) above the nail. During the 5 minutes procedure it is necessary to sit still. It is also recommended to close eyes and try to breathe normally in order to reduce the impact of external factors. Upon completing the recorded data processing, the software draws a conclusion about the body functional state and the stress level with the detailed description of every parameter.

If an examined person has opaque nail polish or athlete’s heart (in that case, anacrotic and dicrotic waves are almost the same), it is impossible to use a pulseoximetry sensor for HRV registration. To perform the procedure, ECG clip electrodes are fixed on arms and legs for the measurement and data are taken in the first standard lead.

CONTRAINDICATIONS
Pulseoximetry with HRV is harmless and painless procedure. There are no contraindications, but a finger on which a sensor placed must be without skin damage.

One day prior the examination it is advisable not to take medications and avoid of physiotherapy procedures (if it is not a monitoring of treatment efficacy). The room temperature should be maintained within +19–23°С.

Before the procedure it is recommended that a person stays in a comfortable sitting or lying position for several minutes. Direct sunlight or bright artificial light must not shine on the pulseoximeter sensor.