How should I wear an ECG watch

We recommend to wear the Vagus ECG smartwatch on the left arm because the placement of the electrode makes it easier to do the ECG tests in that position.

How do I connect the watch with the phone and app?

Set the phone Bluetooth ‘on’.   You do not need to pair or set the Bluetooth connection on the standard Bluetooth settings screen on the watch.    The connection is established by the Vagus Health App and the connection is initiated from the app-device screen.   On the app, go to ‘devices’ and press ‘connect’.    When the connection is established, the app will show ‘connected’ and the watch will show a ‘chain–sign’ on the information screen.    

Why won’t my watch connect to my phone and/or synchronize the data?

Set the phone Bluetooth ‘on’.   On the app, go to devices and press ‘connect’ on the device.    The watch number is shown on the information display on the watch.   This same watch number should be seen as ‘connected’ on the app.  If you have many watches, it is possible that the app is set to connect to another watch and therefore cannot find your active watch.  Disconnect the other watch and search again for devices.  Now activate the right watch.  The watch should show a ‘chain–sign’ on the information screen when it is connected to the app.   If none of these helps, then shut down and restart the watch and shut the app and restart it.   Check if the phone is connected to other Bluetooth devices.  Close those connections.   Bluetooth is unstable especially in older Android or IOS phones and it cannot support many devices simultaneously.    If none of these steps solve the problem, uninstall the app and re-install it from the App- or play store.   If it still does not connect to the phone, check if it works on other phones.

The time on the watch is wrong – how can I set it?

The time cannot be set on the watch itself.  The time is automatically set to phone time when the watch is connected the Vagus Health App.    If the time is not changing due connection or synchronization problems then follow the above instructions in; ‘Why won’t my watch connect to my phone and/or synchronize the data?’

How do I change the watch-face?

Press the watch-face for 3 seconds – it will change automatically.  There are currently three types of watch-faces.

How do I track my heart rate with the watch?

The Vagus ECG smartwatch has dual heart rate measurement methods.  It has a optical pulse sensor which is measuring the pulse with a green light sensor on the bottom of the watch.  The other way to measure pulse is to use the ECG measurement with either the ‘Vagus ECG Test’ or ‘Base ECG Test’.  

How do I track my health and fitness goals with the watch?

The watch is automatically measuring its movement with a so-called x-, y-, z- sensor.  This watch data is then analysed and expressed as steps.   These reported ‘steps’ are naturally not an accurate measurement of each step since the arm never moves in exact synchrony with the legs but it gives a good indication of the daily activity level of the user.   If for instance the user is setting 10000 steps as her or his daily goal – then the outcome as ‘steps’ is usually very well correlated with the persons activity level during that day.   We recommend that users compare their own relative changes in steps from day to day and not to focus on the absolute step count.    We like to remind that the human body and the vagus nerve is holistically influenced and improved by a person’s general movement and activity levels – not only ‘steps’ taken.  We recommend to keep up activity levels for such as regularly ‘rising up’ during longer term sitting down work periods. This ‘upright’ standing activity value is expressed in the activity display of the app.

I only see the notifications on the watch a short time – can I retrieve them?

Currently you only get a vibration and display of incoming messages (msg, whatsapp etc).  If you later want to read old messages you have to do that on your phone.

Can I answer the phone on my watch?

No – it is vibrating and displaying who is calling if you have allowed the app to access your contact information.  You have to answer on your phone.

What is an electrocardiogram, ECG?

An ECG is the recording of the electrical activity of the heart through electrodes.  In the Vagus ECG watch the electrodes are under the watch and on the metal surface on the left side of the watch.  

How do I do an ECG test with the Vagus ECG smartwatch?

To record an ECG, you have to rest your hand on the leg or a table. Then press ‘Vagus Test or ‘Base ECG Test’ on the watch face.  Now place your right hand partly over the watch so that you still see most of the watch face.   Place your right hand’s thumb on the watch’s left side electrode metal surface.  Then follow the instructions shown on the watch.  Sit still while doing the full test.

Is the Vagus ECG smartwatch FDA-cleared – is it a medical device?

No, it is not since we do not provide any medical- or disease diagnostics with the watch.  It is not a medical device and should not be used as such.

Can the watch detect Atrial Fibrillation (AFib)?

No, we do not provide AFib detection.  Atrial Fibrillation (AFib) is a medical condition and some smartwatches are diagnosing it.  Based on our many years of testing, we have concluded that this type of diagnostics has a high degree of false positives.  We do not want to provide a service which potentially needlessly increase user’s anxiety and healthcare spending.  If the user suspects that she or he has a heart health issue or AFib, the user can download the ECG raw-data and PDF-graphical files with the Vagus Health App and send it to a cardiologist for medical evaluation. 

What is the watch detecting automatically?

The watch is automatically detecting movement which it is reporting as steps, calories burned and for how long time the user is standing upright.   The watch is also continuously tracking the optical pulse by measuring the pulse during 1 minute each 10 minutes.   These pulse measurements are displayed in the ‘heart rate’ display window.  When worn during the night, the watch will automatically detect sleep patterns which is displayed in the ‘sleep’ window on the app.

What is the vagus nerve?

The vagus nerve is the most important nerve for long-term health.   It is called the ‘Rest and Digest’ nerve as opposite to the sympathetic nervous system which is called the ‘fight and flight’ system.    The vagus nerve is the longest and most complex of the 12 pairs of cranial nerves.   It transmits information to and from the brain to internal organs in the body such as the gut and heart.   The Vagus nerve is the main component of the parasympathetic nervous system which is also known as the ‘rest and digest’ system.   The ‘opposite’ of this system is the sympathetic nervous system which is known as the ‘fight and flight’ system which is activated when the body is in stress such as during disease progress.  

How do I measure my vagus nerve?

The vagus nerve is usually measured with optical pulse sensors on activity armbands, watches or chest-bands and expressed as heart rate variability (HRV).  HRV only gives a very limited indicator of the vagus nerve activity.  The Vagus ECG Smartwatch measures several types of vagal tones from both optical pulse and ECG (HRV, RSA and RSAsync) and it provides a unique in-depth analytics in the form of the Vagal Homeostasis value.

Why is the vagus nerve important for the heart?

The vagus nerve is synchronizing the heart beats to breathing in order to optimise oxygen delivery to body tissues.   This function is more active when the body is relaxed.   When the body is stressed from mental issues or disease, this heart/breathing synchronization is altered.   This alternation is described by Vagus Health as a RSAsync index and used in the Vagal Homeostasis evaluations.

What is the vagus nerve doing when you breath?

When the vagus nerve is active, it optimises the blood oxygenation by periodically changing the level of oxygen absorption and transfer to the blood in the lungs.   This it does by ‘pulsing’ the lungs oxygen absorption parts in synchrony with its influence on increasing and decreasing the heart rate.   This is a very important functionality of the vagus nerve because it helps to optimize cardiac/respiratory energy consumption and homeostasis.

What is vagal tone?

Vagal tone refers to the level of activity and health of the vagus nerve.   To date, the most common methods to measure vagal tone has been heart rate variability (HRV as SDNN or rMSSD) and respiratory sinus arrhythmia (RSA).  Vagus Health with the Vagus ECG Watch is introducing a new type of vagal tone index which we call Respiratory Sinus Arrhythmia Synchronization (RSAsync).  Traditional vagal tone measurements do not normally address this synchronization periodicity between the timings of the increase or decrease of heart rate in relation to the corresponding inhale or exhale.   The Vagus Health analytics therefore take into account three Vagal Tone values – HRV, RSA and RSAsync.   We do not consider it appropriate and in order to not cause confusion in reference to traditional methods – we do not express this combination as ‘vagal tone.  Instead we describe the health of the vagus nerve by estimating and expressing a value for ‘Vagal Homeostasis’.  The vagal homeostasis level statements in the app are incorporating several biosignals with the traditional values of ‘vagal tone’ and our introduced value ‘RSAsync’.   The word ‘vagal’ is here always used according to the definition ‘relating to the vagus nerve’.

What is homeostasis? How does the vagus nerve influence homeostasis?

Human life requires that many of the body’s interior parameters maintain a ‘magic’ interval known as the homeostatic range.  The process of achieving this balanced state is called homeostasis.  In its broadest sense, homeostasis is considered a description of when the body is self-sustaining and enable to uphold optimum balance for continued natural life spans.    There are also many narrow definitions of homeostasis limiting themselves to certain control centres that for instance enable healthy balance in fluids, temperature, gut-, gene-, immune-, mental-, molecular- and internal cell activities.  Traditionally it is considered that the vagus nerve is an essential part of cardiac-, respiratory-, gut&digestion-, internal organ- and autonomic nervous system homeostasis.  Lately it has been found that it is also a very important part of the mental- and immune homeostasis.  

What is Vagal Homeostasis?   Vagus Nerve Homeostasis Index?

In estimating Vagal Homeostasis, the Vagus Health analytics system take into account three Vagal Tone values – HRV, RSA and RSAsync plus a number of other bio signal parameters measured by the Vagus ECG smartwatch and machine learning individualization based on the user’s data.   The Vagal Homeostasis Index (VHI) is expressed between 0-100 where 100 is a very high level of homeostasis which also can be expressed as a good and healthy ‘balance’ in the autonomic system.   The VHI is a novel test & analytics analysis system invented by Gustaf Kranck and it is pat. pend. for Vagus Health Ltd.  It is only available for Vagus ECG Smartwatch clients.

What is RSA – Respiratory Sinus Arrhythmia?

The RSA value describes the relation between breathing intervals to pulse variation intervals.   In a healthy person, the vagus nerve is optimizing oxygenation of the blood by increasing heart rate when a person inhales and decreasing heart rate at exhaling.  The RSA value is derived from the ‘Vagus ECG Test’ controlled breathing periodicity.  The Vagus Health RSA index is between 0-100 where 100 is a perfect timing-synchronicity between breathing and heart rate peak-to-peaks.

What is RSAsync – Respiratory Sinus Arrhythmia Synchronization?

RSAsync describes the timing and nature of the rising and falling heart rate compared to the corresponding breathing pattern.   When a person inhales, the pulse should rise in order to optimize oxygenation.   When the person exhales, the pulse should go down.   The RSAsync measures how ‘well’ this timing works and it is an indicator of changes to the autonomic and/or immune system.  A higher RSAsync values implies a better oxygenation and healthier vagus nerve.  There can be considerable individual base-line differences for this RSAsync value due to genetical dispositions or longer term changes in the vagal influence of the cardiac/respiratory cycle when a person  for instance has blood pressure issues.  The vagus nerve baroreceptor has a primary over-riding influence on this respiratory-cardiac synchronization periodicity.    We recommend tracking the individual changes to this base-line as indicator of the persons stress-, immune- or for instance anxiety induced changes.  RSAsync is a novel test & analytics analysis system invented by Gustaf Kranck and it is pat. pend. for Vagus Health Ltd.  It is only available for Vagus ECG Smartwatch clients.

Is vagal homeostasis and immunity correlated?

The vagus nerve is a very important part of the immune system.  There is ample evidence that the activity level of the vagus nerve is correlated with a person’s immune system activity.   For instance, HRV measurements in diverse disease syndromes indicate that decreased vagus nerve activity is associated with increased morbidity and mortality.   Immune system changes affect multiple vagus nerve activities and hence we hypothesize that immune changes can be analyzed by doing the Vagus ECG Test.    We hope that crowdsourcing of data with the Vagus ECG smartwatch together with clinical studies will provide further insights to the nature of this correlation between vagal homeostasis and immunity.

What does the pulse values mean?

The pulse in the Vagus ECG Test display is shown as the three ECG recoded heart rate values: 1) Average heart rate.  2) Maximum heart rate as an average of maximum heart rates from each breathing cycle.   3) The minimum heart rate as average of the minimum heart rates from each breathing cycle.  The minimum heart rate is highly correlated with resting heart beat and we recommend placing more attention on this value in the Vagus ECG Test than on the average or maximum heart rates.  

What does the HRV values mean?

Heart rate variability or HRV is the physiological phenomenon of the variation in the time interval between consecutive heartbeats. A normal, healthy heart does not tick evenly like a metronome, but instead to keep the body healthy the vagus nerve is optimising oxygenation by modulating the length between heart beats  to synchronize with breathing.  When doing the Vagus ECG Test, we show the traditional variability as calculated with SDNN during the test and additionally we calculate the (HRmax – Hrmin)/ HR during the controlled breathing phase and establish a variation percentage as a index with a scale of 0-100 where 100 is a very strong variation and 0 is the lack of hear rate variability. 

What does the VHI values mean?

The VHI is short for Vagal Homeostasis index.  The main components in VHI are HRV, RSA and RSAsync.  Additionally the VHI takes into account also a number of other bio signal parameters measured by the Vagus ECG smartwatch and machine learning individualization based on the user’s data.   The Vagal Homeostasis Index (VHI) is expressed between 0-100 where 100 is a very high level of homeostasis which also can be expressed as a good and healthy ‘balance’ in the autonomic system.   The VHI is a novel test & analytics analysis system invented by Gustaf Kranck and it is pat.pend. for Vagus Health Ltd.  It is only available for Vagus ECG Smartwatch clients.

Why is the watch ECG pulse and heart pulse measurements not the same?

The watch is measuring the optical pulse during a 1-minute period each 10 minutes. Therefore, it does not measure pulse during the next 9 minutes. This periodicity is used in order to save battery.   The optical pulse is additionally set so that it does not measure at the same time as ECG because the electrical signals arising from the optical pulse measurements can disturb the ECG electrical signal measurements on the watch. There therefore may be differences between ECG heart rate and Optical Pulse Heart Rate values due to timing reasons.  Another reason for a different heart can also be that he ECG measurement is more accurate than the optically derived heart rate estimations.  Studies have shown that optical hear rate measurements are statistically true only as averages for longer term measurements.

What is the return and warranty policy for the Vagus ECG smartwatch?

The watch has a 12-month warranty or longer according to regional legislation.  If you experience that there is a technical fault in the watch, you may return it for repair or replacement.   Prior to sending it and in order to receive return instructions, you need to send a guarantee claim to [email protected].  More information is in the ‘Terms of Service’ on the Vagus Watch page on