586
R. B. Pachori and V. Gupta
absorbs the incident light as compared to the surrounding tissue. As a consequence,
the intensity of transmitted light decreases for increased arterial radius or at the
time of systole. This method not only assesses the pulsatile changes of the local
blood volume but also assesses the basic level of blood absorption related to blood
oxygenation. The recorded biomedical signal shows similarity with blood pressure
from the carotid artery and mild similarity with blood pressure recorded with the
ascending aorta but no similarity is obtained with the radial artery blood pressure.
Another method is based on mechanical plethysmography which targets local skin
curvature in order to assess a superficial artery such as the carotid artery on the neck.
During arterial cardiac deflections, the curvature of the local skin changes and it can
be assessed by a skin curvature sensor [34].
12.5.1.4 Blood Oxygenation
Blood circulation implies a rhythmic transportation of oxygenated and deoxygenated blood from the lung and back to the lung. Hence, the blood oxygenation
level is a vital physiological parameter which is usually extracted with optical
biomedical signals. In this method, the light absorption due to pulsatile arterial
blood is measured at two wavelengths and interrelated by an algorithm. The
blood oxygenation level is usually maintained at a fairly constant level. Thus, the
monitoring of blood oxygenation level is very important in order to diagnose cardiac
and vascular anomalies. This examination is more specific for anesthesiology to
prevent an inadequate oxygen supply. The presence of oxygen in arterial blood is
due to binding of oxygen molecules with hemoglobin and dissolving of oxygen
with blood plasma in gaseous state. However, the quantity of oxygen in the
blood is mainly due to hemoglobin oxygenation as blood plasma carries a very
less amount of oxygen. Therefore, the oxygenated hemoglobin implies as a local
oxygen buffer to maintain the partial pressure of oxygen in the plasma. On the
other hand, the reduced hemoglobin reserves oxygen in the pulmonary capillaries
by depleting partial pressure of oxygen in the plasma, resulting in oxygenated
hemoglobin. Although blood plasma contains a negligible amount of oxygen, it
plays an important role in delivering oxygen to the tissues and the storing of oxygen
in the pulmonary capillaries by hemoglobin. It should be noted that the noninvasive
assessment of blood oxygen level in the elderly is faced with progressing accuracy
problems by optical method [34].
12.5.1.5 Body Temperature
The temperature of the human body is generally governed by the heat production
and loss. During rest condition, the heat production is usually carried out by the
inner organs such as kidneys, liver, heart, intestines, and brain under the scope
of metabolic activity. The rest condition in metabolic activity generally consumes
almost 50–70% of daily energy. During normal condition, the inner organs produce
R. B. Pachori and V. Gupta
absorbs the incident light as compared to the surrounding tissue. As a consequence,
the intensity of transmitted light decreases for increased arterial radius or at the
time of systole. This method not only assesses the pulsatile changes of the local
blood volume but also assesses the basic level of blood absorption related to blood
oxygenation. The recorded biomedical signal shows similarity with blood pressure
from the carotid artery and mild similarity with blood pressure recorded with the
ascending aorta but no similarity is obtained with the radial artery blood pressure.
Another method is based on mechanical plethysmography which targets local skin
curvature in order to assess a superficial artery such as the carotid artery on the neck.
During arterial cardiac deflections, the curvature of the local skin changes and it can
be assessed by a skin curvature sensor [34].
12.5.1.4 Blood Oxygenation
Blood circulation implies a rhythmic transportation of oxygenated and deoxygenated blood from the lung and back to the lung. Hence, the blood oxygenation
level is a vital physiological parameter which is usually extracted with optical
biomedical signals. In this method, the light absorption due to pulsatile arterial
blood is measured at two wavelengths and interrelated by an algorithm. The
blood oxygenation level is usually maintained at a fairly constant level. Thus, the
monitoring of blood oxygenation level is very important in order to diagnose cardiac
and vascular anomalies. This examination is more specific for anesthesiology to
prevent an inadequate oxygen supply. The presence of oxygen in arterial blood is
due to binding of oxygen molecules with hemoglobin and dissolving of oxygen
with blood plasma in gaseous state. However, the quantity of oxygen in the
blood is mainly due to hemoglobin oxygenation as blood plasma carries a very
less amount of oxygen. Therefore, the oxygenated hemoglobin implies as a local
oxygen buffer to maintain the partial pressure of oxygen in the plasma. On the
other hand, the reduced hemoglobin reserves oxygen in the pulmonary capillaries
by depleting partial pressure of oxygen in the plasma, resulting in oxygenated
hemoglobin. Although blood plasma contains a negligible amount of oxygen, it
plays an important role in delivering oxygen to the tissues and the storing of oxygen
in the pulmonary capillaries by hemoglobin. It should be noted that the noninvasive
assessment of blood oxygen level in the elderly is faced with progressing accuracy
problems by optical method [34].
12.5.1.5 Body Temperature
The temperature of the human body is generally governed by the heat production
and loss. During rest condition, the heat production is usually carried out by the
inner organs such as kidneys, liver, heart, intestines, and brain under the scope
of metabolic activity. The rest condition in metabolic activity generally consumes
almost 50–70% of daily energy. During normal condition, the inner organs produce