Heart Rate Variability
Nerve-Express is a method for quantitative assessment of the Autonomic Nervous System (ANS) based on Heart Rate Variability (HRV) analysis.
Prior to the application of HRV to ANS assessment, the Autonomic function could only be approximately assessed by the following three parameters:
- Autonomic Balance (Vegetative Homeostasis)
- Sympathetic Prevalence
- Parasympathetic Prevalence.
Traditionally, the criteria used for evaluating these three parameters were clinical and laboratory findings.
Assessment of the Autonomic function was thus labor intensive and not always feasible.
The introduction of HRV analysis - especially, the identification of the power of low-frequency band of 2 HRV spectral function with the activity of Sympathetic Nervous System (SNS) and the power of its high-2 frequency band with the activity of Parasympathetic Nervous System (PSNS) - opened up new theoretical opportunities for ANS assessment. But to make practical use of this important scientific discovery one had to solve the problem of deriving some form of quantitative relationship between SNS and PSNS from the spectral function.
HRV analysis is based on measuring variability in heart rate; specifically, variability in intervals between R waves - “RR intervals” (cf. Fig. 1). These RR intervals are then analyzed by spectral (as in Nerve-Express) or some other form of mathematical analysis (e.g., chaos, wavelet theories). Such mathematical analysis generates multiple parameters; typically 20-30. The problem of SNS-PSNS quantification, which has remained for many years the principal dilemma of HRV analysis, is specifically in reducing all possible variations of these multiple parameters to a quantitative relationship between only two parameters: SNS and PSNS.