Pulse oximetry is a noninvasive test that uses light to measure the oxygen saturation level in a person's blood. A clip-like probe is placed on the finger or earlobe and uses red and infrared light wavelengths absorbed differently by oxygenated and deoxygenated hemoglobin to calculate the oxygen saturation percentage. This information helps healthcare providers determine if a patient needs supplemental oxygen or how well treatment is working. However, pulse oximetry has limitations as it does not measure other blood gas levels, ventilation, or oxygen metabolism and can be affected by factors like carbon monoxide, anemia, blood flow, and skin pigmentation.

1. PULSE OXIMETRY
DR.MAHESWARI JAIKUMAR
maheswarijaikumar2103@gmail.com

2. • Pulse oximetry is a test used to
measure the oxygen level
(oxygen saturation) of the blood.
It is an easy, painless procedure
to assess the oxygen saturation

3. • Pulse oximetry is clip-like device
called a probe is placed on a body
part, such as a finger or ear lobe.
The probe uses light to measure
how much oxygen is in the blood.
• This information helps the
healthcare provider decide if a
person needs extra oxygen.

4. PARTS OF PULSE OXIMETER

6. INDICATIONS FOR PULSE
OXIMETRY
• During or after surgery or
procedures that use sedation
• To see how well lung medicines are
working

7. • To check a person’s ability to
handle increased activity levels
• To see if a ventilator is needed to
help with breathing, or to see
how well it’s working

8. • To check a person has moments
when breathing stops during
sleep (sleep apnea)

9. • Pulse oximetry is also used to check the
health of a person with any condition that
affects blood oxygen levels, such as:
• Heart attack
• Heart failure
• Chronic obstructive pulmonary disease
(COPD)
• Anemia
• Lung cancer
• Asthma
• Pneumonia

10. TYPES OF PUSE OXIMETRY
• TRANSMISSIVE APPLICATION MODE
• REFLECTANCE PULSE OXIMETRY

11. MODE OF ACTION
• In its most common (transmissive)
application mode, a sensor device is
placed on a thin part of the patient's
body, usually a fingertip or earlobe,
or in the case of an infant, across a
foot.

12. • The device passes two wavelengths of
light through the body part to a photo
detector. It measures the changing
absorbance at each of the wavelengths,
allowing it to determine
the absorbances due to the
pulsing arterial blood alone,
excluding venous blood, skin, bone,
muscle, fat, and (in most cases) nail
polish.

13. FINGER SENSOR

14. • Reflectance pulse oximetry is a less
common alternative to transmissive
pulse oximetry. This method does
not require a thin section of the
person's body and is therefore well
suited to a universal application
such as the feet, forehead, and
chest, but it also has some
limitations.

15. • Vasodilation and pooling of venous
blood in the head due to compromised
venous return to the heart can cause a
combination of arterial and venous
pulsations in the forehead region and
lead to spurious SpO2 results.
• Such conditions occur while undergoing
anesthesia with endotracheal
intubation and mechanical ventilation
or in patients in the Trendelenburg
position

17. FUNCTION
• A blood-oxygen monitor displays
the percentage of blood that is
loaded with oxygen.
• More specifically, it measures what
percentage of hemoglobin, the
protein in blood that carries oxygen,
is loaded.

19. • Acceptable normal ranges for
patients without pulmonary
pathology are from 95 to 99
percent. For a patient breathing
room air at or near sea level, an
estimate of arterial pO2 can be
made from the blood-oxygen
monitor "saturation of peripheral
oxygen" (SpO2) reading.

20. • A typical pulse oximeter uses an
electronic processor and a pair of
small light-emitting diodes (LEDs)
facing a photodiode through a
translucent part of the patient's
body, usually a fingertip or an
earlobe.

22. • One LED is red, with wavelength of
660 nm, and the other
is infrared with a wavelength of
940 nm. Absorption of light at these
wavelengths differs significantly
between blood loaded with oxygen
and blood lacking oxygen.

24. • Oxygenated hemoglobin absorbs
more infrared light and allows more
red light to pass through
• Deoxygenated hemoglobin allows
more infrared light to pass through
and absorbs more red light.

25. • The LEDs sequence through their
cycle of one on, then the other, then
both off about thirty times per
second which allows the
photodiode to respond to the red
and infrared light separately and
also adjust for the ambient light
baseline.

26. • The amount of light that is transmitted
(in other words, that is not absorbed) is
measured, and separate normalized
signals are produced for each
wavelength.
• These signals fluctuate in time because
the amount of arterial blood that is
present increases (literally pulses) with
each heartbeat.

27. • By subtracting the minimum
transmitted light from the
transmitted light in each
wavelength, the effects of other
tissues are corrected for, generating
a continuous signal for pulsatile
arterial blood.

28. • The ratio of the red light
measurement to the infrared light
measurement is then calculated by
the processor (which represents the
ratio of oxygenated hemoglobin to
deoxygenated hemoglobin), and
this ratio is then converted to
SpO2 by the processor via a lookup
table based on the Beer–Lambert
law

29. • The signal separation also serves other
purposes: a plethysmograph waveform
("pleth wave") representing the
pulsatile signal is usually displayed for a
visual indication of the pulses as well as
signal quality,and a numeric ratio
between the pulsatile and baseline
absorbance ("perfusion index") can be
used to evaluate perfusion.

30. ADVANTAGES
• Pulse oximetry is convenient
for noninvasive continuous
measurement of blood oxygen
saturation.
• Whereas blood gas levels must
otherwise be determined in a
laboratory on a drawn blood
sample.

31. • Pulse oximetry is useful in any
setting where a
patient's oxygenation is unstable,
including intensive care, operating,
recovery, emergency and hospital
ward settings, pilots in
unpressurized aircraft, for
assessment of any patient's
oxygenation, and determining the
effectiveness of or need for
supplemental oxygen.

32. • Although a pulse oximeter is
used to monitor oxygenation, it
cannot determine the
metabolism of oxygen, or the
amount of oxygen being used by
a patient.

33. • Therefore, it is necessary to also
measure carbon dioxide (CO2)
levels.
• It can also be used to detect
abnormalities in ventilation.

34. • However, the use of a pulse
oximeter to
detect hypoventilation is impaired
with the use of supplemental
oxygen.
• Therefore, the routine
administration of supplemental
oxygen may be unwarranted if the
patient is able to maintain adequate
oxygenation in room air

35. • Because of their simplicity of use and
the ability to provide continuous and
immediate oxygen saturation values,
pulse oximeters are of critical
importance in emergency medicine and
are also very useful for patients with
respiratory or cardiac problems,
especially COPD, or for diagnosis of
some sleep disorders such
as apnea and hypopnea.

36. LIMITATIONS
• Pulse oximetry solely measures
hemoglobin saturation,
not ventilation and is not a complete
measure of respiratory sufficiency.
• It is not a substitute for blood
gases checked in a laboratory, because it
gives no indication of base deficit,
carbon dioxide levels, blood pH,
or bicarbonate (HCO3
−) concentration

37. • The metabolism of oxygen can be
readily measured by monitoring expired
CO2, but saturation figures give no
information about blood oxygen
content.
• Most of the oxygen in the blood is
carried by hemoglobin; in severe
anemia, the blood contains less
hemoglobin, which despite being
saturated cannot carry as much oxygen.

38. • Erroneously low readings may be caused
by hypoperfusion of the extremity being
used for monitoring (often due to a limb
being cold, or
from vasoconstriction secondary to the
use of vasopressor agents); incorrect
sensor application;
highly calloused skin; or movement
(such as shivering), especially during
hypoperfusion.

39. • To ensure accuracy, the sensor
should return a steady pulse
and/or pulse waveform.
• Pulse oximetry also is not a
complete measure of circulatory
oxygen sufficiency.

40. • If there is insufficient bloodflow or
insufficient hemoglobin in the
blood (anemia), tissues can
suffer hypoxia despite high arterial
oxygen saturation.

41. • Since pulse oximetry measures
only the percentage of bound
hemoglobin, a falsely high or
falsely low reading will occur
when hemoglobin binds to
something other than oxygen:

42. • Hemoglobin has a higher affinity to
carbon monoxide than it does to
oxygen, and a high reading may
occur despite the patient's actually
being hypoxemic.
• In cases of carbon monoxide
poisoning, this inaccuracy may delay
the recognition of hypoxia (low
cellular oxygen level).

43. SUMMARY
• Limitations in Using a Pulse Oximeter
• Carbon Monoxide. Carbon monoxide molecules,
even in a small amount, can attach to the patient's
hemoglobin replacing oxygen molecules.
• Hemoglobin Deficiency (Anemia)
• Blood Volume Deficiency.
• Irregular Signals.
• External Interference.
• Fingernail Polish and Pressed on Nails.
• Skin Pigmentation.
• Intravenous Dyes.

44. NORMAL RANGE FOR PULSE
OXIMETRY
• Normal pulse oximeter readings
usually range from 95 to 100
percent. Values under 90 percent
are considered low.

45. FACTORS AFFECTING PULSE
OXIMETRY READING
• Blood pressure generally needs to be >80
SBP.
• Vascular impingement from any cause.
• AV fistula can decrease distal flow.
• Elevation with respect to the heart.
• Compression by the probe.
• Cardiac arrest (don't use during arrest)
• Heart Rate extremes <30 or >200. Cold. Fear
(Endogenous catecholamines) Medications.

46. REFERENCES
• Jørgensen JS, Schmid ER, König V, Faisst K, Huch A, Huch R (July 1995).
"Limitations of forehead pulse oximetry". Journal of Clinical Monitoring. 11 (4):
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• ^ Matthes K (1935). "Untersuchungen über die Sauerstoffsättigung des
menschlichen Arterienblutes" [Studies on the Oxygen Saturation of Arterial
Human Blood]. Naunyn-Schmiedeberg's Archives of Pharmacology (in
German). 179 (6): 698–711. doi:10.1007/BF01862691.
• ^ Millikan GA (1942). "The oximeter: an instrument for measuring continuously
oxygen saturation of arterial blood in man". Review of Scientific
Instruments. 13(10): 434–
444. Bibcode:1942RScI...13..434M. doi:10.1063/1.1769941.
• ^ Jump up to:a b Severinghaus JW, Honda Y (April 1987). "History of blood gas
analysis. VII. Pulse oximetry". Journal of Clinical Monitoring. 3 (2): 135–
8. doi:10.1007/bf00858362. PMID 3295125.
• Jopling MW, Mannheimer PD, Bebout DE (January 2002). "Issues in the
laboratory evaluation of pulse oximeter performance". Anesthesia and
Analgesia. 94 (1 Suppl): S62–8. PMID 11900041.

47. THANK YOU