Method and apparatus for measurement of autonomic nervous system function

Abstract

The invention analyzes relationships between factors, within a patient population, to identify autonomic dysfunction patterns. Patient test results are then compared with the identified patterns to determine the patient's autonomic function. The invention can continually amend the patient population with new test results to create increasingly accurate normative data sets from which a patient's autonomic function can be more accurately assessed. The invention may apply this concept in an application service provider model. An embodiment of the invention may use a novel method of identifying ECG R-waves. The method locates R-waves by searching for maximum slope values, in signals, that exceed threshold values. Another embodiment of the invention entails a non-provocative HRV test whereby certain time domain and frequency domain factors are analyzed to determine a patient's autonomic function.

Description

BACKGROUND INFORMATION [0001] 1. Technical Field [0002] The present invention relates to apparatuses and methods for measuring autonomic nervous system function. [0003] 2. Description of the Related Art [0004] The autonomic nervous system (ANS) is primarily responsible for the fine-tuned regulation of many human organs and systems. An individual whose autonomic nervous system correctly regulates such organs and systems is said to have good autonomic function. Improper autonomic function may be referred to as autonomic dysfunction, which can be the result of autonomic neuropathy (AN). AN can result in improper regulation of organs and systems, which in turn may lead to the malfunction of those organs and systems. AN is often associated with a number of disorders such as diabetes and coronary artery disease. In fact, the last two decades have witnessed the recognition of a significant relationship between AN and cardiovascular mortality, including sudden cardiac death. Thus, testing f...

AI Technical Summary

Benefits of technology

[0018] While the methods for performing the Metronomic, Orthostatic and Valsalva tests produce valuable information regarding autonomic function, prior art methods and equipment fail to take full advantage of the available information. For instance, in the prior art, normative databases for HRV values are not created and maintained. As an illustration, the prior art does not attempt to determine normal VARmax values for patients according to such diverse factors as race, age, smoking history and gender. Consequently, the VARmax value of a black, 30-year old, non-smoking man is often compared with that of a 30-year old, white woman who has smoked for 10 years. Doing so may lead to an inaccurate assessment of the male patient's autonomic function. Furthermore, the prior art does not attempt to link certain factors such as race, age and VARmax value with a risk factor for contracting, for example, hypertension. An additional limitation in the prior art is the inability to provide normative databases that expand, and whose accuracy is refined as HRV studies continue to be performed. Finally, the prior art requires expensive, complicated and burdensome HRV testing equipment that many non-specialists are unlikely to use. As a result, AN associated maladies, such as heart disease and diabetes, are not assessed as well as possible because the vast majority of clinicians do not possess these complex tools.

[0019] Therefore, a method and apparatus for measuring autonomic nervous system function is needed that can help patients gain early notice when they are at risk for developing an illness forecasted or indicated by poor autonomic function. In addition, a need exists for specific normative databases that provide targeted HRV information that focuses on both demographic and health factors. Such a normative database should help discern HRV patterns to allow clinicians to better assess potential health issues for patients. The normative database should continue to expand and provide more valuable forecasting and assessment tools as HRV studies are conducted over time. Finally, a need exists for HRV testing which is available through an Application Service Provider model so practitioners need not invest heavily in sophisticated equipment that must be updated regularly. Such testing capabilities would become a powerful tool in the clinician's hands for early detection of various medical problems before those maladies show any clinical manifestation. Furthermore, such capabilities would better allow health care providers to assess progress or deterioration in a patient's previously assessed autonomic dysfunction.

[0020] In one embodiment of the invention, background data from a population of patients is obtained. The population of patients may be comprised of patients with both normal and abnormal autonomic function. Then, the invention may receive ECG data from the same population of patients. HRV parameters such as NNmin SB and SD may be measured from the ECG data. Afterwards, discriminant analysis may be performed on the HRV parameters and background data to determine discriminant equations, wherein each discriminant equation discriminates between patients with normal and abnormal autonomic function. For instance, patterns may be identified whereby certain HRV parameter measurements, when combined with certain background information, such as race and gender, may distinguish between individuals with early signs of diabetes and those without such signs. After these equations are developed, new patients may be tested. Each new patient provides background data and HRV data. Then, the invention may select, from among the discriminant equations it has previously developed from the data from the population of patients, only those equations that pertain to the particular patient being tested. Consequently, data from a 20 year old black woman may be compared to other 20 year old black women, each afflicted with a different malady. The new patient's HRV data could then be input into the selected equations to provide autonomic rankings that are indicative of the new patient's autonomic function. In one embodiment of the invention, the background and HRV data from each new patient may be added to the same information that exists for the population of patients thereby creating increasingly larger normative data sets from which future patients' autonomic function can be more accurately assessed.

Problems solved by technology

AN can result in improper regulation of organs and systems, which in turn may lead to the malfunction of those organs and systems.

This results in a change in blood pressure.

While the methods for performing the Metronomic, Orthostatic and Valsalva tests produce valuable information regarding autonomic function, prior art methods and equipment fail to take full advantage of the available information.

As an illustration, the prior art does not attempt to determine normal VARmax values for patients according to such diverse factors as race, age, smoking history and gender.

Doing so may lead to an inaccurate assessment of the male patient's autonomic function.

Furthermore, the prior art does not attempt to link certain factors such as race, age and VARmax value with a risk factor for contracting, for example, hypertension.

An additional limitation in the prior art is the inability to provide normative databases that expand, and whose accuracy is refined as HRV studies continue to be performed.

Finally, the prior art requires expensive, complicated and burdensome HRV testing equipment that many non-specialists are unlikely to use.

As a result, AN associated maladies, such as heart disease and diabetes, are not assessed as well as possible because the vast majority of clinicians do not possess these complex tools.

Images