Chapter 3
Pulse Oximetry for the Measurement
of Oxygen Saturation in Arterial Blood
Jagadeesh Kumar V. and K. Ashoka Reddy
Abstract The method of photoplethysmography (PPG) detailed in Chapters 1 and
2 gained enormous prominence due to the development of pulse oximetry. In pulse
oximetry, the fact that hemoglobin bound with oxygen (called oxyhemoglobin)
and hemoglobin without oxygen (deoxy-hemoglobin or reduced hemoglobin)
absorb/reflect light differently is exploited in ascertaining, noninvasively, oxygen
saturation in arterial blood. Most pulse oximeters that are in existence today use a
couple of PPGs obtained using red and infrared wavelength light sources and calculate oxygen saturation in arterial blood using the red and IR PPGs and an empirical
equation. This chapter details the development of pulse oximetry. It describes in
detail a couple of novel methods of oxygen saturation calculation using the red and
IR PPGs. The methods presented here do not need any calibration to be performed.
3.1 Physiological Signals for Diagnostics
Dynamic and static measurements on the physical, electrical, chemical and acoustic
signals of a human body will help ascertain its health [1–3]. Whenever a person
is affected by a disease or gets injured, one or more of these physical, electrical,
chemical and acoustic signals change. However, these physical, electrical, chemical
and acoustic signals also change day to day due to natural variations in the life
cycle. Moreover, the changes in these signals are a complex combination of different
parameters. Hence it is very difficult to delineate the functioning or malfunctioning
of the underlying biological parts or processes directly from these signals. The four
traditional vital signs, namely, the pulse rate, the respiratory rhythm (and sound), the
body temperature and the blood pressure are normally used by medical practitioners
all over the globe to assess a patient’s state of health. In the modern times, a fifth vital
signal, namely, the oxygen saturation in blood has also gained importance. Today
any patient with coronary or pulmonary problems must be evaluated for the oxygen
J. Kumar V. (B) · K. A. Reddy
Indian Institute of Technology Madras, Chennai, India
e-mail: vjkumar@ee.iitm.ac.in
© Springer Nature Singapore Pte Ltd. 2021
V. Blazek et al. (eds.), Studies in Skin Perfusion Dynamics,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-981-15-5449-0_3
51
Pulse Oximetry for the Measurement
of Oxygen Saturation in Arterial Blood
Jagadeesh Kumar V. and K. Ashoka Reddy
Abstract The method of photoplethysmography (PPG) detailed in Chapters 1 and
2 gained enormous prominence due to the development of pulse oximetry. In pulse
oximetry, the fact that hemoglobin bound with oxygen (called oxyhemoglobin)
and hemoglobin without oxygen (deoxy-hemoglobin or reduced hemoglobin)
absorb/reflect light differently is exploited in ascertaining, noninvasively, oxygen
saturation in arterial blood. Most pulse oximeters that are in existence today use a
couple of PPGs obtained using red and infrared wavelength light sources and calculate oxygen saturation in arterial blood using the red and IR PPGs and an empirical
equation. This chapter details the development of pulse oximetry. It describes in
detail a couple of novel methods of oxygen saturation calculation using the red and
IR PPGs. The methods presented here do not need any calibration to be performed.
3.1 Physiological Signals for Diagnostics
Dynamic and static measurements on the physical, electrical, chemical and acoustic
signals of a human body will help ascertain its health [1–3]. Whenever a person
is affected by a disease or gets injured, one or more of these physical, electrical,
chemical and acoustic signals change. However, these physical, electrical, chemical
and acoustic signals also change day to day due to natural variations in the life
cycle. Moreover, the changes in these signals are a complex combination of different
parameters. Hence it is very difficult to delineate the functioning or malfunctioning
of the underlying biological parts or processes directly from these signals. The four
traditional vital signs, namely, the pulse rate, the respiratory rhythm (and sound), the
body temperature and the blood pressure are normally used by medical practitioners
all over the globe to assess a patient’s state of health. In the modern times, a fifth vital
signal, namely, the oxygen saturation in blood has also gained importance. Today
any patient with coronary or pulmonary problems must be evaluated for the oxygen
J. Kumar V. (B) · K. A. Reddy
Indian Institute of Technology Madras, Chennai, India
e-mail: vjkumar@ee.iitm.ac.in
© Springer Nature Singapore Pte Ltd. 2021
V. Blazek et al. (eds.), Studies in Skin Perfusion Dynamics,
Biological and Medical Physics, Biomedical Engineering,
https://doi.org/10.1007/978-981-15-5449-0_3
51