Surgery – Diagnostic testing – Measuring electrical impedance or conductance of body portion
Reexamination Certificate
2000-09-14
2002-12-03
Peffley, Michael (Department: 3736)
Surgery
Diagnostic testing
Measuring electrical impedance or conductance of body portion
C600S587000
Reexamination Certificate
active
06490480
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the invention
The invention relates to an apparatus and non-invasive methods to assess autonomic nervous system (ANS) function. By simultaneous recording of electrophysiological and other physiological signals, a complete indication of ANS function can be obtained in just one diagnostic test instead of numerous separate tests.
The autonomic nervous system (ANS) is concerned with the regulation of smooth muscle, cardiac muscle and every other visceral organ in the body. The autonomic nervous system is not directly accessible to voluntary control. Instead, it operates in an automatic fashion on the basis of autonomic reflexes and central control. One of its major functions is the maintenance of homeostasis within the body. The ANS further plays an adaptive role in the interaction of the organism with its surroundings. The ANS has two functionally and anatomically distinct divisions: the sympathetic part and the parasympathetic part.
In many diseases the sympathetic and the parasympathetic parts of the ANS are affected leading to autonomic dysfunction. The evaluation of the presence of ANS disorders requires in interpretation of numerous laboratory tests like blood pressure measurements, heart-rate and respiration-rate recordings, evaluation of the endocrine system and tilt table tests etc. In our prior U.S. Pat. No. 5522386 we disclose a new polygraphical method called electroautonomography (EAG), which can be used to determine the central and/or peripheral ANS function including the autonomic innervation and control of major organ systems as well as of local ANS function. The method is based on the polygraphical recording of skin potentials or electrodermal activity and is called electrovegetography. The electrovegetograph as described in our previous art is based on a sensitive (AC or DC) amplifier means specifically capable of registering skin potentials. Generally skin potentials are recorded with an AC amplifier in combination with the filter settings within the following band pass 0.1-40 Hz. A typical skin potential registration contains skin potential frequencies approximately between 0.033 and 0.33 Hz and amplitudes that can range between 0.05-2.0 mV. These values are based on rest recordings before the occurrence of habituation. The initial high amplitudes are thought to be a result of the subject's emotional status. After several minutes the amplitudes decrease to a level that reflect ANS activity. Upon stimulation the amplitude of the skin potentials may raise up to 5 mV. The extent of the reaction to the stimulus is thought to be largely depended on the subject's ANS activity.
The determination of the so called autonomic nerve conduction velocity or NCV can be more accurately performed using the fast waves obtained from skin potential recordings, because these fast waves display a sharp onset of an evoked response, whereas the “normal skin potentials” do not always display a sharp onset and especially not after the occurrence of habituation. This characteristic of “normal” skin potentials complicates the calculation of the autonomic nerve conduction velocity, resulting in wrong calculations of the NCV. In practice this may mean for instance that a beginning neuropathy is not detected, whereas the calculation of the NCV using the fast waves is much less susceptible for mistakes even after the occurrence of habituation, and will therefore facilitate the early diagnosis of neuropathy and other disorders that affect the autonomic nerve fibers. The fast waves can also be used to detect a neuropathy in any part of the mammalian body.
The fast waves can be further used in an alternative microneurographic measurement method. Microneurography or intraneural recording is an invasive technique, which is used to assess sympathetic activity. For such a measurement a needle microelectrode is inserted directly into a nerve.
It is therefore an object of this invention to use a non-invasive method to measure fast waves of the skin potentials and any other electrophysiological signals.
It is also an object of this invention to determine autonomic conduction velocity presented by fast wave recordings to evaluate the autonomic nerve system's function.
It is further object of this invention to provide an early and accurate diagnostic test for many diseases of autonomic dysfunction.
SUMMARY OF THE INVENTION
The objects set forth above as well as further and other objects and advantages of the present invention are achieved by the embodiments of the invention described hereinbelow.
The present invention relates to an apparatus and methods to measure any type of electrophysiological signals and especially the measurement of skin potentials characterized by low frequency oscillations and high frequency oscillations. These types of skin potentials are called slow waves and fast waves respectively. As “normal” skin potentials the slow waves and fast waves are suggested to be generated by and to be under control of the ANS.
The slow waves can be detected preferably with a DC amplifier means. The “normal” skin potentials are superimposed on the slow waves. The slow waves can be detected preferably with the high pass filter switched off and the low pass filter set at 0.01 Hz. The observed wavelengths with these filter settings may range between 24 hours and 2 minutes, whereas the amplitudes may vary between 100_V and 5 mV in rest recordings. The amplitude may change with values up to 25 mV upon stimulation. We suggest that these slow waves reflect cycles in metabolism and ANS and most likely sympathetic activity.
The fast waves can be measured with a sensitive DC amplifier means, but are more preferably measured with a sensitive AC amplifier means. In order to detect the fast waves, the band pass of the filters need to be set at 0.1-40 Hz, preferably the band pass is set at 0.5-30 Hz and more preferably the band pass is set at 1-10 Hz, The frequencies of the observed fast waves may range between 2-15 Hz, but frequencies higher than 15 Hz do also exist. The amplitudes of the fast waves may range between 2 and 200_V. These fast waves are generated by and under the control of ANS activity, particularly by parasympathetic activity. The fast waves are not only present in the spectrum of skin potentials, but they can be present in any electrophysiological signal that is recorded superficially or with a needle electrode inserted in any organ or tissue of a mammal's body. The slow and fast waves possibly reflect the tone of the ANS.
The following analysis method may be used in a preferred embodiment for the fast waves, and the existing signal:
The letters refer to amplitudes in either _V or mV at the maximum respectively and minimum, whereas the figures refer to the time periods in either milliseconds or seconds. The Roman figures refer to the area under the curve of each of the four segments. Now we will call the quotient: [A/1] the negative reactivity index and the quotient: [A/2] the negative recovery index of the wave. The quotients [B/3] and [B/4] will be the curve's positive reactivity and positive recovery indices respectively. We further suggest to define the time segments 1+2 as _a; the time, segments 3+4 as the whole period (1+2+3+4) as _, which is a commonly used symbol for the wavelength.
From a selected portion of the measured values, all the described parameters are averaged and for each index (negative and positive reactivity, negative and positive recovery, _a, _b, _and area) its relative occurrence in a selected part of the measured values is calculated. Healthy organisms will have indices within a certain range whereas organisms with a dysfunctional ANS will have indices that deviate from the indices range of healthy ones.
In addition to the measurement of skin potentials, the apparatus is further adapted to measure any other in practice known electrophysiological signal like but not limited to the electrocardiogram, the electro-encephalogram, the electrogastr
Nixon & Vanderhye P.C.
Peffley Michael
Wingood Pamela Lynn
LandOfFree
Apparatus and methods for measuring autonomic nervous system... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Apparatus and methods for measuring autonomic nervous system..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Apparatus and methods for measuring autonomic nervous system... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2969221