This invention relates in general to a technique for monitoring the effectiveness of medication taken to treat Attention Deficit Hyperactivity Disorder (ADHD) and more particularly to a technique for measuring an individual's peripheral temperature variability (TV) indicative of ADHD.
ADHD is the most common neurobehavioral disorder of childhood as well as among the most prevalent health conditions affecting school-aged children. Between 4% and 12% of school age children (several millions) are affected. $3 billion is spent annually on behalf of students with ADHD. Moreover, in the general population, 9.2% of males and 2.9% of females are found to have behavior consistent with ADHD. Upwards of 10 million adults may be affected.
ADHD is a difficult disorder to diagnose. The core symptoms of ADHD in children include inattention, hyperactivity, and impulsivity. ADHD children may experience significant functional problems, such as school difficulties, academic underachievement, poor relationships with family and peers, and low self-esteem. Adults with ADHD often have a history of losing jobs, impulsive actions, substance abuse, and broken marriages. ADHD often goes undiagnosed if not caught at an early age and affects many adults who may not be aware of the condition. ADHD has many look-alike causes (family situations, motivations) and co-morbid conditions (depression, anxiety, and learning disabilities) are common.
Diagnosis of ADHD involves a process of elimination using written and verbal assessment instruments. However, there is no one objective, independently validated test for ADHD. Various objective techniques have been proposed but have not yet attained widespread acceptance. These include:
2. Infrared tracking to measure difficult-to-detect movements of children during attention tests combined with functional MRI imaging of the brain were used by psychiatrists at McLean Hospital in Belmont, Mass to diagnose ADHD in a small group of children (Nature Medicine, Vol. 6, No. 4, April 2000, Pages 470-473).
There are several clinical biofeedback and physiologic monitoring systems (e.g. Multi Trace, Bio Integrator). These systems are used by professional clinicians. Although skin temperature spectral characteristics have been shown to indicate stress-related changes of peripheral vasomotor activity in normal subjects, there has been no disclosure of use of variations in skin-temperature response to assist in diagnosing ADHD. (See: Biofeedback and Self-Regulation, Vol. 20, No. 4, 1995).
As discussed above, the primary method for diagnosing ADHD is the use of a bank of written and verbal assessment instruments designed to assess the children for behavioral indicators of criteria established by American Medical Association (AMA) as described in the Diagnostic and Statistics manual—IV (DSM-IV). Psychiatrists, psychologists, school psychologists and other licensed practitioner administer these assessment instruments. In some cases those individuals who meet DSM-IV criteria for ADHD diagnosis are prescribed a drug such as Ritalin. Behavioral observations of the patient while on Ritalin are conducted to assess the impact of prescribed medication. However, clearly established criteria for evaluating the impact of specific medications e.g., Ritalin and specific dosages are lacking. It would be advantageous for physicians to have access to clearly established physiologic criteria, which could be measured, to determine if a specific medication at a specific dosage effectively addressed the underlying physiologic parameter, which was indicative of ADHD.
There is thus a need for a simple, inexpensive, and reliable technique for determining the effectiveness of the medication and appropriate dosage taken to counteract ADHD by an individual who has ADHD.
According to the present invention, there is provided a solution to the problems and fulfillment of the needs discussed above.
According to a feature of the present invention, there is provided a a method for determining the appropriate dosage of a medication to treat Attention Deficit Hyperactivity Disorder (ADHD) in an individual who has ADHD comprising:
Advantageous Effect of the Invention
The invention has the following advantages.
1. A device and technique for determining the effectiveness of the medication and appropriate dosage taken to counteract ADHD by an individual whom has ADHD which is simple, inexpensive and reliable.
a and 3b are block diagrams of a system incorporating the present invention.
According to the invention, it has been found that a signature of ADHD is hidden in fluctuation of the temperature of the skin as measured at the extremities such as at a fingertip as a function of variations in stress level. In general, as an individual's stress level increases the peripheral vasculature constricts and often the person's blood pressure increases. As the blood vessels in the body constrict, blood flow is restricted. This is most easily monitored in the extremities such as the fingers, because the blood vessels in the extremities are small and very responsive to Sympathetic Nervous System (SNS) innervations. A direct result of decreased blood flow to the blood vessels in the extremities is a decrease in the peripheral temperature of the extremities. Conversely, as an individual's stress level decreases and relaxation occurs, the blood vessels expand, allowing blood to flow in a less restricted manner. As the blood flow to the vessels in the extremities increases the peripheral temperature of the extremities increases. It is suspected that when a subject with ADHD is subjected to sensory deprivation such as being made to look at a blank screen or an obscured image for a period of time in an inactive state, the lack of stimulation increases and there tends to be a shift in the subject's physiologic reactivity indicative of an increase in their stress level. As their stress level increases their blood vessels contract and the peripheral temperature of their extremities decreases. Biofeedback practitioners have long used measurement of hand temperature to help subjects manage their physiology by controlling blood flow to the extremities. The literature reports that reduced blood flow to the brain is frequently found in patients with ADHD.
In addition to peripheral skin temperature and peripheral skin temperature variability there are other known physiologic measures which are known (or potential) indicators of stress and therefore ADHD such as; bilateral temperature variability, heart rate, heart rate variability, muscle tension (excessive and chronic, measured via surface electromyography—sEMG), bilateral muscle tension imbalance, galvanic skin response (i.e., electro dermal response—EDR), eye saccades, blood oxygen (SpO2), salivary IGA, electroencephalography (EEG), peripheral blood flow (measured via photoplethismography—PPG), and peripheral blood flow variability (PPG).
As shown in
As shown in
In
Now referring to
FFT (fm)=A(fm)+B(fm)i
In the equations 1.0 and 1.1 the subscript l refers to the fact that a separate signal is extracted for each hand so the subscript is l for data extracted from the left-hand data and r for data from the right hand.
Raw Data
The raw data Tk,l(t) is the temperature taken from hand l at a fingertip 16 as shown in
Referring again to
Windows
The data for each session were divided into a series of windows (block 43) prior to performing the Fourier Transform operation. Call the window width w. In this analysis, the window width was 64 seconds and there were 10 windows spaced at 50-second intervals (the windows overlap) across the 600 sec baseline spanning the range of 100-500 sec, other values of w can be used. The window number in a session is referred to with the letter j. For each window a FFT algorithm calculates the Fourier Transform F(f). The Magnitude and Phase of this transform are defined as given above.
In block 46 the range of magnitude variation during a window is calculated using equation (1.2) below where fmax and fmin are the frequencies where the Magnitude is the greatest and the least respectively (note the dc component at frequency zero is excluded).
Mrange=[M(fmax)−M(fmin)] (1.2)
In a further embodiment of this method, other statistics from a Fourier Transform, calculated from the quantities denoted above as A (fm), B (fm), θ (fm), and M (fm) may be used. In addition to using Fourier Transforms, this further embodiment may use statistics derived from a Wavelet transform of data or other filtering of the data (as in Strang, G. and Nguyen, T. (1996), Wavelets and Filter Banks, Wellesley-Cambridge Press, Wellesley, Mass.).
Aggregation of Samples
MRange values for all windows are aggregated in block 47. There are z windows from each hand from each session. The first step is to choose an aggregation statistic, which can be the mean, median, variance, or other statistic, which is an aggregate of the computed Mrange values in each window for each session and each hand. Other statistics that may be used for aggregation include the standard deviation, range, interquartile distance, skewness, kurtosis, Winsorized mean and variance, and robust estimates of mean and variance. Equations below are given for aggregating the mean and the variance. The mean magnitude range for the left hand during session k is found from equation 2.0 where z is the number of windows in the session.
And the corresponding variance is:
Combining these session means and variances over both hands and all the sessions s that a subject attended gives an aggregated mean μ and aggregated variance.
Further embodiments of this aggregation step include using the data from only one hand—either the left hand, the right hand, or the dominant hand (and if the subject is ambidextrous, the dominant hand would be defined as the average of both hands). In addition, future embodiments may not require averaging of several sessions, but selecting only one session for use or using a weighted combination of each session's results.
Diagnostic Indicators
Referring again to
When the subject's measured aggregation statistic Θm (from equation 2.2 or 2.3) block 47 is less than the group threshold θg-block 50, the test indicates the subject has ADHD. When the measured aggregation Θm statistic is greater than the predetermined threshold θg, the test indicates the subject does not have ADHD-block 50 and no medication is required-block 51. The same threshold θg may be used for all subjects or θg may have a value that is different for different groups based on gender or age.
Determination of Proper Dosage
Now referring to
Dosage=100×(θg−Θm−1)+100×gender
where the dosage is in milligrams of a drug, and where gender is coded as 0 if the patient is female and 1 if the patient is male. For example, if θg=10 and Θm=8, and the patient is male, the example formula would call for a dosage of 100×(10−8−1)+100×1=200 milligrams of the drug.
Medication Effectiveness Indicator
If the prescribed medication is effective in correcting the ADHD, then the measured physiologic diagnostic indicator Θm (as defined by equation 2.2 or 2.3) would be expected to come within the normal range and exceed θg during the time the patient is medicated.
In studies using this method, subjects who had ADHD were tested while on medication and again while not on medication. The diagnostic indicator Θm was higher on average when the subject was medicated, and lower on average when the subject was not medicated. This is consistent with what the hypothesis would predict. Paired t-tests (for example, see Hildebrand, D. K. and Ott, L. (1991), Statistical Thinking for Managers, PWS-KENT Publishing, Boston, p. 440) showed this change in Θm was statistically significant (α=0.05), indicating that the method described was able to determine changes brought about by the medication.
When we let Θm be the mean Mrange,
When Θm is the median Mrange, the results are shown in
When Θm is the variance of the Mrange, the results are shown in
Thus, to determine if the dosage is effective, the patient will be re-tested according to the following procedure as illustrated in
Because a patient's physiology can change over time, the effective dosage may change over time as well. Thus, the patient needs to be monitored during the treatment period in accordance with the best medical practices. One such monitoring scheme, which should be followed during the entire time the patient is taking the drug, is to periodically re-test the patient. The interval between these periodic tests can for example, be one month to one year. The monitoring procedure involves repeating blocks 70-78. In one embodiment of the invention, the initial dosage found-block 78 could be replaced with an enhancement in which, if Θm exceeds θg by a large amount, the dosage is decreased, while if Θm exceeds θg by a small amount, then the proper dosage has been found.
The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.
This patent application is a Continuation-in-Part Application of U.S. patent application, Ser. No. 09/865,329 filed May 25, 2001, which application claims the benefit under 35 USC § 120 of the earlier filing date of U.S. patent application Ser. No. 09/597,610, filed Jun. 20, 2000, now U.S. Pat. No. 6,394,963.
Number | Date | Country | |
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Parent | 10301401 | Nov 2002 | US |
Child | 10856126 | May 2004 | US |
Number | Date | Country | |
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Parent | 09865329 | May 2001 | US |
Child | 10301401 | Nov 2002 | US |