Oximeter: - “The life saving Instrument”
R.G AJAY PRAKASH AND DHRITI SUNDER MISHRA
B.E THIRD YEAR, 6 SEM, PROF.P G KUMARVELU
M.S. RAMAIAH INSTITUTE OF TECHNOLOGY, BANGALORE-560054 (KARNATAKA)
Ajayprakash27@gmail.com & email@example.com
Category:- biomedical instrumentation.
Abstract: - In today’s world it becomes quite important to have a self-sustained and highly
efficient instrument in the medical world. Today when the whole world is progressing such fast
and now we have developed highly efficient designs in the medical world. There are still some
instruments in which there is possibility of more improvement in their designing and application
with the human body. Theirs is a need of technology and instrument which is less invasive and
play a vital role in life saving. That is why we call the medical world the “field of opportunity”.
Oximeter is used for the calculation of the oxygen saturation of the circulating arterial blood. Their
role in the medical field is extraordinary. Although the technology which is in the market is less
invasive and make it a better instrument of its kind. There are many types but the most common
type is PULSE OXIMETER .it is mainly based on “transmission Oximetry principle”. When the
same oximeter works on the reflectance principle becomes more stable so it plays a vital role in our
So we are concentrating on its design and the technology used that can make it a instrument of
tomorrow. And the ways in which we can make it more accurate and less invasive and more user
friendly cost effective and can give readings with less error.
PO in the hospital never gets highlighted but when the patient is suffering from anoxia cardiac and
vascular abnormalities, this instrument plays a vital role. It is also helpful in the diagnosis of
postoperative anoxia and the treatment of anoxia resulting from pulmonary affections. Also due to
the advancement in the design it can also play a vital role in determining the malfunctioning of the
organs such as lungs, heart etc.
Before operating the patient in OperatinTheatre anesthesia is given at that time this instrument help
in prevention of tissue hypoxia, it provides immediate and direct information about the level of
tissue oxygenation. Oximetry therefore now considered as a “standard of care in anesthesiology”.
It has significantly reduced anesthesia-related cardiac deaths.
Advanced points to focus:-
Improved design, more accuracy, less costly, and its application in other treatments.
OT: - Operation Theatre (present in hospitals)
PO: -Pulse Oximeter
TOP: - transmission Oximetry principle
There is no doubt that pulse Oximetry represents the greatest advance in patient monitoring in
many years. It has the unique advantage of continuously monitoring the saturation of hemoglobin
with oxygen, easily and noninvasively, providing a measure of cardio-respiratory function. By
virtue of its ability to quickly detect hypoxemia, it has become the standard of care during
anesthesia as well as in the recovery room and intensive care unit. Pulse Oximetry should be used
to monitor any patient who is heavily sedated or is likely to become hypoxic. The fundamental
physical property that allows the pulse oximeter to measure the oxygen saturation of hemoglobin is
that blood changes color as hemoglobin absorbs varying amounts of light depending on its
saturation with oxygen. Oxyhemoglobin does not absorb much red light, but as the hemoglobin
oxygen saturation drops, more and more red light is absorbed and the blood becomes darker. At the
near infrared range of light however, oxyhemoglobin absorbs more light than reduced hemoglobin.
PULSE OXIMETRY BASED UPON TWO PHYSICAL PRINCIPLES:-
a) The light absorbance of oxygenated hemoglobin is different from that of reduced hemoglobin, at
the oximeter two wavelengths, which include red and near infrared light; and
b) The absorbance of both wavelengths has a pulsatile component, which is due to the fluctuations
in the volume of arterial blood between the source and the detector.
Given these two facts, clever engineering techniques have produced an invaluable monitor.
RELATION BETWEEN RESPIRATION AND OXIMETRY :-
The goals of respiration are to provide oxygen to the tissues and to remove carbon dioxide. To
achieve these goals, respiration can be divided into four major functions: (1) pulmonary
ventilation, which means the inflow and outflow of air between the atmosphere and the lung
alveoli; (2) diffusion of oxygen and carbon dioxide between the alveoli and the blood; (3)
transport of oxygen and carbon dioxide in the blood and body fluids to and from the body’s tissue
cells; and (4) regulation of ventilation and other facets of respiration.
Now we are familiar with the process, when the blood once get oxygenated it is carried to the heart
to be pumped to the different parts of the body with the help of highly efficient pumping machine
i.e. heart. This oxygenated blood with the help of brachial artery is carried out to the index finger
where the concentration levels of oxygen are measured with the help of pulse oximeter, as the
finger is the most suitable and the instrument cab be placed easily and can be monitored more
RELATION BETWEEN HEART AND OXIMETRY:-
As we know the heart pumps the blood to the different parts of the body and our concern is with
the oxygenated blood so if the Oximetry is done on the arteries near to the heart such as brachial
artery can help us in getting the information on the precise condition of the heart also apart from
the regular oxygen monitoring. In Oximetry we consider for measurement the pulsatile component
of the blood this pulsatile component of blood is generated due to the pulses which are generated
due to the rhythmic nature of the heart. Before taking the reading we check the pulse rate for 10
sec to know the condition of the patient, after properly fixing the instrument if later the
concentration decreases it may be due to the deviation in the rhythmic behavior of the heart or due
to the decrease in the pressure of blood into the artery it may be due to the artery blockage because
if any artery blocks the pressure after the block decreases and the pressure inside the heart
increases which in turn leads to the changes in the rhythm of the heart and also due to the less
pressure the tissues also show the variation of oxygen concentration which becomes quite
noticeable as you move away from the heart, the most affected part is the brain as of 30% oxygen
is utilized by it, As the alarm condition is generated the patient should be asked to take ECG and
PROBLEMS IN THE PREVIOUS MODELS WHICH ARE APPROACHED:-
• The effect of a length of probe.
• False low pulse Oximetry reading associated with the concomitant use of a peripheral
nerve stimulator and an evoked-potential stimulator.
• The effect of henna paste on oxygen saturation reading obtained by pulse Oximetry
• Effects of interferences, dyes, dyshaemoglobins and other pigments.
• Effects of changes in saturation and signal quality.
• Some more conditions are noticed in the hospital while testing, which change the design of
oximeter. In some hospitals(msr hospital) we found patients which are not mentally stable
or if in sub conscious condition, they were not allowing the sensor to be stably connected
to the finger which results into the errors due to motion artifact and many time alarm was
raised due to its disconnection with the finger as the subject feel it discomfort and easily
removes it from there if this is unmonitored then it can be life taking for the patients who
are recovering from the heart surgery or hypoxic condition so its solution is efficiently
• Now if the subject if prone to the environment where the oxygen concentration levels in the
environment are low will results into the low levels of oxygen concentration into the blood
specially seen in the Indian soldiers at the high altitudes in Leh and Srinagar. (Jammu and
Kashmir).so there is need for baseline values to be revised there should be separate mode.
• Soldiers have to keep on moving in vehicles and most of the times the emergency care does
not have quality ambulance, also while travelling in heavy traffic it becomes very difficult
to differentiate the alarm sound.
SOLUTIONS OF THE PROBLEMS:-
• With different length probes the test was repeated again and again and on the same finger
of the patient whose mean oxygen concentration was known after laboratorial blood
testing and it was found that when the length was less than 1.5 meters the readings were
more accurate so it was made as compulsory to restrict the length in between 1 meters. So
in the design the length of cable/probe is strictly restricted to 1mtrs and hence the errors
due to the length and also the signal distortion is reduced.
• Due to the use of the evoked potential stimulator(in 2 special cases in I.C.U) the pulsatile
component of the blood adds with the response produced due to these evoked potentials
and results into the rise in the value if the pulses are superimposed and if the pulse
response is not superimposed then results into the decrease from the actual reading take
place. so while taking reading it was taken care that the patient’s on which the test is to be
performed should be free of such stimulators.
• After testing on about twenty volunteers it was found that there is error due to the
presence of nail polish on the nails specially in women’s and it become quite time
consuming procedure to remove the nail polish properly. And sometime in order to make it
adjustable we have to cut the nails which again made the instrument not feasible for those
who are fashion lovers. so we improve the sensor design so that it can suit to all.
• And in 3 patients we found that due to the presence of some dye which was given to them
while treatment some errors were there to overcome this the instrument was recalibrated
and a +-1% was allowed in the reading. Because internal dyes needs time to be washed out
and they increase the light absorbing capacity.
• Since the change of values in concentration was very small so the readings are sufficiently
amplified so that a small change can become noticeable.
• Along with the sensor a special lock system was implemented due to which the case of
accidental removal of the sensor from finger become almost zero and if the patient tries
also he cannot remove it, so false alarm raising was stopped.
• It is tried to design so precise that it can be able to work in rough conditions such as
-50celcius, at high altitudes. And also automatic-calibration for low oxygen saturation
• Along with the alarm capability it is also incorporated with a screen for the display of the
signal which provide a audio visual alarm for low concentrations.
Patients having different heart disorders were tested along with their ECG and the
continuous monitoring of their oxygen concentration in the body is done with oximeter the
low levels of oxygen concentration were detected far more before any condition which is
shown in the ECG has actually arrived in them specially in case of epileptic patients and it
was noteworthy the levels of oxygen before the actual epileptic attack has felled to almost
78%.and during the attack it was nearly 68% which shows a severe hypoxic condition .
ECG 1 during mild attack
Arterial defibrillation condition:-
• Display- LCD, Backlight illuminated
• Parameters and waveform displayed- SPO2, pulse rate, system status, plethysmogram,
menus for user settings
• SPO2 range- 0-100 %
• Accuracy of SPO2- +3%
• Pulse rate range should be 0-240 bpm
• Audiovisual Alarms- High/low SPO2 and pulse rate, sensor off, sensor failure,
• low battery
• Alarm override facility
• Cable length should be minimum 1 meter
• RS 232C Interface for data communication.
• Integrated Printer
• Battery back-up operating time 5 hours internal & rechargeable.
DESIGN PROTOTYPE MODEL FOR THE SENSOR:-
The above design measurement readings are in mm.
• Simple, portable "all-in-one" monitor of oxygenation, pulse rate and rhythm regularity,
suitable for "field" use.
• As a safe, non-invasive monitor of the cardio-respiratory status of high-dependency
patients - in the emergency department, during general and regional anesthesia,
postoperatively and in intensive care. This includes procedures such as endoscopy, where
often frail patients are given sedative drugs such as midazolam. Pulse oximeters detect the
presence of cyanosis more reliably than even the best doctors when using their clinical
• During the transport of patients - especially when this is noisy - for example in aircraft,
helicopters or ambulances. The audible tone and alarms may not be heard, but if a
waveform can be seen together with an acceptable oxygen saturation, this gives a global
indication of a patient's cardio-respiratory status.
• To assess the viability of limbs after plastic and orthopedic surgery and, for example,
following vascular grafting, or where there is soft tissue swelling or aortic dissection. As a
pulse oximeter requires a pulsatile signal under the sensor, it can detect whether a limb is
getting a blood supply.
• As a means of reducing the frequency of blood gas analysis in intensive care patients-
especially in pediatric practice where vascular (arterial) access may be more difficult.
• To limit oxygen toxicity in premature neonates supplemental oxygen can be tapered to
maintain an oxygen saturation of 90% - thus avoiding the damage to the lungs and retinas
of neonates. Although pulse oximeters are calibrated for adult hemoglobin, HbA, the
absorption spectra of HbA and HbF are almost identical over the range used in pulse
Oximetry, so the technique remains reliable in neonates.
• During thoracic anesthesia - when one lung is being collapsed down - to determine whether
oxygenation via the remaining lung is adequate or whether increased concentrations of
oxygen must be given.
• Fetal Oximetry- a developing technique that uses reflectance Oximetry, using LEDs of
735nm and 900nm. The probe is placed over the temple or cheek of t fetus, and needs to be
sterile and sterilisable. They are difficult to secure and the readings are variable, for
physiological and technical reasons. Hence the trend is more useful than the absolute value.
Clinicians have come to rely on pulse oximeters. In good faith judgments are based on the
data they give. The reliability of the data is very dependent on the accuracy of the sensor. If
the accuracy of the sensor is unknown, every clinical decision made, that is based on the
data is without foundation
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