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different matching algorithms including modified distance function, similarity matrix
and fuzzy similarity matching. Finally, as an output, the best matched case is pre-
sented i.e. a classification of the individual stress level which can be used to deter-
mine an individual's sensitivity to stress.
4 Finger Temperature Signal and Stress
In general, finger temperature decreases when a person is stressed and increases dur-
ing relaxation or in a non-stressed situation. This relates to mainly sympathetic inter-
vention of the alpha-receptor in the vascular bed. When relaxation occurs, activity of
the sympathetic nervous system decreases as well as the intervention of the alpha
receptors, which leads to increased dilation of the blood vessels which increases blood
flow and temperature [8]. The reverse situation occurs during stress i.e. the sympa-
thetic nervous system activates causing a decrease in peripheral circulation which
leads to decreased skin temperature. Thus the blood flow in the finger temperature
responds also to changes in emotional state. In clinical practice, the activities of the
automatic nervous system (i.e. balance between the sympathetic and parasympathetic
nervous systems) are monitored as a part of diagnosis of psychophysiological dys-
functions. Therefore, the rise and fall of finger temperature as illustrated in Fig. 3 can
help to diagnose stress-related dysfunctions or dysfunctional behaviours; it is also an
effective parameter for patients with Raynaud's syndrome [43]. Some conventional
methods of diagnosing stress include measuring one or a combination of the follow-
ing: respiration e.g. end-tidal carbon dioxide (ETCO2), heart rate e.g. calculating the
respiratory sinus arrhythmia (RSA) and heart rate variability (HRV). One of the ad-
vantages of using FT in diagnosing stress is that the diagnosis and biofeedback
training is often less expensive than using these other conventional measures, which
require equipment not suitable for use in a non-clinical environment and cannot be
used without experienced clinical staff. Since it is not always possible to provide
clinical staff with laboratory facilities to measure many different parameters (often
using many sensors) a supplementary convenient tool that can be used at any time and
any place to diagnose and control stress for a general user is important. A temperature
sensor can be used to collect finger temperature by attaching it to the finger. The FT
signals from the sensor readings during different stress and relaxed conditions can be
transmitted as an electronic signal to a computer screen. Thus it can serve as a con-
venient method to diagnose and treat stress i.e. give biofeedback to normalize stress-
related dysfunctions at home and at work for general users. Also it can be used as an
auxiliary medical system for clinical treatment.
4.1 Analysis of Finger Temperature Sensor Signal
Ideally the temperature is monitored repeatedly for short intervals during a longer
period, i.e. a week, to determine the temperature consistency or pattern of the person.
Some example signals are illustrated to show the individual variations. It has been
observed from the measurements that different people have different representative
temperatures, e.g. some may have representative temperature of 27° C as the lowest
temperature while for other people 32° C may be the lowest. An example of different
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