Abstract :
Regular and non-invasive assessments of
cardiovascular function are important insurveillance for
cardiovascular catastrophes and treatment therapies of chronic diseases.Resting
heart rate, one of the simplest cardiovascular parameters, has been identified as anindependent risk
factor (comparable with smoking, dyslipidemia or hypertension) for
cardiovascular disease [1]. Currently, the gold standard techniques for
measurement of thecardiac pulse such as the electrocardiogram (ECG) require patients
to wear adhesive gel patches or chest straps that can cause skin irritation and
discomfort. Commercial pulseoximetry sensors that attach to the fingertips or
earlobes are also inconvenient for patientsand the spring-loaded clips can cause pain if worn over
a long period of time.
The ability to monitor a patient¶s physiological signals
by a remote, non-contactmeans is a tantalizing prospect that would enhance the
delivery of primary healthcare. For example, the idea of performing physiological measurements on
the face was first postulated by Pavlidis and associates [2] and later
demonstrated through analysis of facial thermalvideos. Although non-contact
methods may not be able to provide details concerning cardiacelectrical conduction that ECG offers, these
methods can now enable long-term monitoring of other physiological signals such
as heart rate or respiratory rate by acquiring themcontinuously in an
unobtrusive and comfortable manner.
Beyond that, such a technology would also minimize the amount of cabling
andclutter associated with neonatal ICU monitoring, long-term epilepsy
monitoring, burn or trauma patient monitoring, sleep studies, and other cases
where a continuous measure of heart-rate is important. The use of photoplethysmography (PPG), a low cost
and non-invasivemeans of sensing the cardiovascular pulse wave (also called the
blood volume pulse) throughvariations in transmitted or reflected light, for
non-contact physiological measurements has been investigated recently. This electro-optic technique
can provide valuable informationabout the cardiovascular system such as heart
rate, arterial blood oxygen saturation, blood pressure, cardiac output and
autonomic function.
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