Hi

I hope that following attached paper and link be helpful, plz check out.

Have a nice day

https://en.wikipedia.org/wiki/Heart_rate_variability

Hello, my research team and I are conducting a study in elderly population measuring HRV with 24h holter monitors. When we started to analyze the preliminary results I wonder to myself exactly the same thing about TP. HRV is like a gray field in cardiology and in medicine but I found it very interesting. Even in the guidelines of HRV measuring (written in 1996 with no update!!, i think), there is a little or no information about TP. This measure reflects overall autonomic activity where sympathetic activity is a primary contributor. So I think it gives you a broad image of autonomic activity. Thus, if it is over the upper limit (again, i do not know if there is stablished values or cut off values), i tells you one of two component (sympathetic may be) is overfunctioning. I know it is kind of useless. But I think it could be also an N-N variable measurement if we take it from certainly point of view. We can state that TP is the approximate frecuency domain correlate to SDNN.

I wouldn´t say that it represents blood flow but I am not sure.

Let me consult this with the expert cardiologist who is interpreting for us the HRV studies and I will be back with something more specific I hope. 

Let me share with you some articles i consider interesting and i hope you find them useful.

Although many researchers already interpreted TP as the total autonomic activity, it is not very accurate to compare it between individuals or groups for the following reasons:

- in general, physiological signals are usually contaminated by noise (specially ECG due to the non-invasive nature of obtaining it). That is why it is known that spectral analysis of those signals provides, strictly speaking, only estimates of power in the analyzed signal!

- Particularly, the TP estimate of HRV is more prone to such errors, due to the inclusion of power within a wide frequency range, compared to signals in which researshers are interested in a narrow frequency band (e.g. Just around the respiratory frequency peak). Actually very early in the field the concept of normalization (Low and High frequency components to the total power) was introduced to minimize such errors upon comparing LF & HF between groups!

- All together can make comparing the TP of HRV between individuals misleading!

I hope that was of any use.

P.S. There is a review by Persson entitled spectrum analysis of time series. Check it out!

Autonomic nervous system or autonomic nervous system, system dynamics that regulate smooth muscle function, muscle, heart and endocrine related. In other words, this part of the peripheral nervous system (PNS), which branches move to smooth muscle, cardiac muscle and glands in the body sends. Since the system at a subconscious level and almost autonomous acts to be named. Of course, this part of the nervous system through the brain stem, chest parts e-lumbar (T1 to L2) spinal cord, sacral spinal cord (S2 to S4) associated with the central nervous system and ultimately by the hypothalamus, cerebellum and frontal lobe of the brain regulates be. The function of this part of the nervous system that is divided into two parts: the sympathetic nervous system and the parasympathetic nervous system is divided. While believed to be sympathetic to emotional reactions such as anger and fear machine comes in, it is known that on the contrary, while the parasympathetic system operation and provide peace and tranquility will prevent sympathetic and naturally and slowly plays a role in everyday activities.Also, we know that HRV Reverse signal RR And autonomic power depends on the PSD 

In general, the parasympathetic nervous system is a proprietary system response, which tend to save energy. The system can be activated at the same time sympathetic system in terms of invasion and escape. Stimulation of the sympathetic system and the parasympathetic nervous system causes the opposite effects to keep living in a situation of calm and without stress. Heart rate and blood pressure decrease, increases the activity of the gastrointestinal tract and bronchial constriction occurs contraction of the pupil. Mental activity also reduced the activity of this system. To an intense fear sacral parts of the system may be evacuated involuntary bladder and rectum. During an erection in the penis and clitoris sexual activity of the parasympathetic system controls and helps to ejaculate mutually sympathetic branches. Despite the knowledge that currently exists in relation to these two parts of the autonomic system, be sure that more will be known about the function of this system. For example, it seems that the complex relationship between visceral afferent nerves and skin sympathetic autonomic system. That's why some skin sensory stimulation can influence the activities of some internal organs. Research in recent years has shown that the autonomic system can be through modulation techniques, manipulated. In terms of medical, physiological and anatomical factors Gellhorn researcher explained that in terms of effective stress and relax.

The heart rate variability (HRV) signal is a useful and non-invasive tool for the evaluation of cardiovascular system and Autonomic Nervous System. Many researcher tried to model this signal. There are many different approaches for this modelling. One of the most frequently used method is Integral Pulse Frequency Modulator (IPFM) model. In IPFM model there is an input signal which is fed to an integrator and when the output of the integrator reaches to a threshold then we have a pulse. This pulse simulates the R-wave of the ECG signal. The source of ECG is sinoatrial (SA) node. SA node is affected by many factors. The power spectrum of HRV signal is divided into three main bands i.e. VLF, LF and HF. The information in these three bands shows how the Autonomic Nervous System (ANS) affects on heart activity. The ratio LF/HF is related to sympathovagal balance. The proposed model generates both normal HRV and HRV of some abnormalities with regard to ANS. As we used random signal in the input of the IPFM the output of the model has random variations and the output never be as a periodic signal. Our model is very similar to real HRV than a normal IPFM.

Dear Dominik, dear all,

Please see below our observations on the physiological meaning of the total power (TP) of the HRV.

First, from the mathematical perspective, the total power is SDNN^2 (SDNN being the standard deviation of RR intervals) and consider here the mean of HRV is removed since not relevant here (mean value of HRV will provide the average heart rate). So TP, SDNN and, at some extend, the RMSSD are reflecting the total variation of HRV around its mean value. Physiologically speaking, it provides the range of variation of the overall autonomic regulation, so the range where the regulation can vary for each individual.  

We have conducted (see attached graph) a study on the HRV amplitude (SDNN) with 100 subjects and we have observed the following conclusions:

- TP/SDNN decrease with age (already outlined by some other published studies)

- having a regular physical activity allows to maintain a higher TP/SDNN for individuals compared to the average value related to the age

- stress and absence of physical activity leads to a lower TP/SDNN compared to average "age" value

- elite athlete have much higher TP/SDNN compared to non athletes

- arrhythmias will increase "artificially"  by a significant factor TP/SDNN so such values are meaningless for interpretation in that case  

- a low TP/RMSSD coupled to an ANS sympatho-vagal imbalance is systematically associated to negative physical and psychological feelings  

So TP/SDNN is a good marker to be seen as an individual evolution history and also with respect to the average value based on subject's age. We can make the hypothesis that having a high TP/SDNN, better is in term of physiological (and likely emotional) regulation and adaptation.     

Another important aspect is measurement protocol and conditions. For instance, under spontaneous respiration the measurement time should be much longer than under controlled respiration. But waiting too long can also might impact the reputability of the results because of the non-stationary nature of the HRV (the TPTP/SDNN can change over the time or upon calculation window).             

Hope this helps!

.    

It is known that HRV reflects the level of general health but, more importantly that HRV is an active process that serves as a tool to provide baroreflex functioning. Each heart beat causes the afferent fire from baroreceptors that promotes inhibition process in the brain. HRV provides the continual, bidirectional communication between the heart and brain, which allows the individual to precisely adapt to changes in his/her internal milieu and external environment by integrating neural and cardiovascular reactions. This information is necessary for interpretation of the HRV indices, in particular, HRV total.

Total power of the HRV reflects current person adaptability.

Perhaps one way to get a better handle on this is to look at what HRV and TP do in various psychiatric diseases. As a short term measure based on individual stress response patterns, it is not clear to me that higher HRV or TP to baseline is necessarily better, although this seems to be commonly accepted.

HRV is not only marker of health but active physiological process that modulates blood flow in body and brain. Thus, HRV modulates activity of the baroreceptors which enhance inhibitory processes in the brain mitigating stress and emotions. LF and VLF oscillations in blood flow caused by HRV physically thru carotid arteries modulates BOLD in the brain structures stimulating their job.

@EGVaschillo - Agreed but autonomous function, which is partially reflected by HRV, also enhances (or reflect the enhancement) of excitatory processes too as well as compensation for past over/under adjustment and anticipated (future) demands (represented by cognition, stress, fatigue, and emotions ...). The measure then may reflect both the under/overshooting of the system as well as the need for necessary adjustment. We assume that a more dynamic system is healthy and a lot of data supports this. However, it also appears to be similar to more exercise (which requires adjustment and higher HRV) and movement is better.