Poincare plot is a very intuitive graphical presentation of our heart pulse data. Characteristic patterns emerge when consecutive heart beat intervals – denoted as RR(i), RR(i+1) – are displayed as dots in x,y plane.
Human heart rate is regulated by autonomous nervous system. Sympathetic response accelerates our heart while parasympathetic response slows it down. Sensitive biofeedback loop controls our heart rate in stressful situations. Driving a car, writing an exam, playing games on xbox or breathing – all that affects our heart rate. Even when completely at rest the intervals between consecutive heart beats varies for tens or even hundreds of milliseconds.
Everyone knows that in stressful situation our heart rate increases. Less known fact is that stress reduces variations of RR – our heart beat becomes very deterministic. When feeling relaxed RR intervals become more random.
Poincare plots above show the effect of physiological stress on person’s heart . The left one shows RR data after moderate workout – 30 minutes of quick walking. Cigar-like pattern is clearly seen along the diagonal line. Person’s heart rate slowly decreases from 75 bpm to 64 bpm average towards the end of the 5 minute measurement. Narrow shape of the cigar indicates small RR variations between consecutive beats – a clear signal of moderate stress caused by previous physical activity. The long axis of the cigar represent slow systemic drift of the persons’s heart rate towards the resting value – which is typical for a post physical activity.
One hour after the workout another measurement is done (upper right plot). Average heart rate is slightly elevated at 50 bpm. RR pattern is more random, indicating lower but still elevated level of stress. Note the change in PNN50 from 2.19% to 34.92% – an indicator of RR variability.
Another interesting example is sudden emotional stress represented on Poincare plot below. Stressor causes instant increase in person’s heart rate to 90 bpm from resting state of 42 bpm. Measurement is then taken for couple of minutes and fast drift of RR intervals towards the resting value is cleary seen. Graph on the lower right side shows resting RR, with an average heart rate of 42 bpm and significant random variations of RR indicating low stress level.
Stress Check 2 uses novel algorithm to determine physiological stress. The whole measurement takes approximately one minute and does not require any special device apart from your smart-phone and the app. Stress Check 2 also tracks mood level – with one simple gesture user defines her Positivity and Energy. Results from the physiological stress measurement, Positivity and Energy defines overall Stress index.
Stress is a silent killer. Most chronic diseases, like type 2 Diabetes, Cardiovascular diseases, Cancer, etc., are triggered by chronic stress and decrease in the efficacy of our immune system. We could lower our Stress by being conscious of our lifestyle. Stress Check 2 will help you in that effort by tracking stress level and stressors through your life.