1. Pulse Oximeter
R. C. Gupta
S. S. Ahluwalia
CSIO, Chandigarh

2. Pulse Oximeter
 Pulse Oximeter is a medical electronic instrument that measures
Oxygen Saturation (SaO2), the percentage of Hemoglobin saturated
with Oxygen & Pulse Rate by Non Invasive technique
 In this the absorption of light by oxygenated and reduced
hemoglobin is measured optically at two wavelengths (RED at 660
nm & Infrared at 940 nm)
 It enables prompt recognition of Hypoxemia in patients
 This instrument is immensely useful in monitoring arterial
oxygenation in paediatrics including Neonatal Units, OTs, Post-
operative Recovery Wards, Trauma Wards. Oximetry has been
recommended as a standard instrument for general anaesthetic
 Pulse Oximetry is also used in monitoring of Pulmonary diseases
in adults & in investigation of sleep disorders

3. Pulse Oximeter
 Oxygen is transported in blood in two distinct states : under
normal physiological conditions, about 98% of Oxygen in the blood
is combined with Hb inside the RED blood cells. The remaining 2%
is physically dissolved in the plasma
 The amount of O2 bound to Hb in a given quantity of arterial blood
is usually represented by the percent SaO2 which is defined as the
ratio of Oxy Hemoglobin (HbO2) concentration to the total
concentration of Hb
HbO2
SaO2 % = ---------------------- X 100
( HbO2 + Hb )

4. Pulse Oximeter
Principle
Oximetry works by trans-illuminating the tissue containing an
arterial blood and evaluating absorption of RED & INFRARED light
i) The light absorbance of oxygenated Hemoglobin (HbO2) is different
from that of reduced Hemoglobin (Hb) at the Oximeter’s two
wavelengths

5. Pulse Oximeter
Principle
ii) The absorbance at both wavelengths have pulsatile (AC)
component, which is the result of fluctuating volume of arterial
blood between source and detector

6. Pulse Oximeter
The output light at each wavelength consists of two
components, referred to as AC & DC components respectively
Based on Beer’s law, Mendelson and Kent derived the relation
between SaO2 and R/IR ratio
ε IR(Hb) (R/IR) - ε R(Hb)
SaO2 =
[ε IR(Hb) – εIR(HbO2)] (R/IR) + [ε R(HbO2) – εR(Hb)]
Where ε (Hb) & ε (HbO2) are millimolar extinction coefficients of
reduced & oxyhemoglobin respectively
R / IR = A 660 nm / A 940 nm = (ACR / DCR) / (ACIR / DCIR)

7. Pulse Oximeter
ε IR(Hb) = 0.20 εR(Hb) = 0.86
ε IR(HbO2) = 0.29 εR(HbO2) = 0.12
Calibration Curve

8. 1 V P-P
50 Hz
CONTROL
SIGNAL
Pulse Oximeter
GENERATOR
PULSE SHAPING
VACR CIRCUIT
LED
DRIVERS
VACR
Red LED IR LED RED CHANNEL
660nm 940 nm SEPARATOR
SAMPLE
RED
HOLD
SUBTRACTOR FILTER OF MULTIPLIER ADC
&
AC & DC
COMPONENT
SaO2 AND
PULSE RATE
DISPLAY
FINGER TIP
AMBIENT
I/V
SAMPLE
HOLD LIGHT µP with
CONVERTER
CHANNEL I/O
&
& memories
PHOTO
DETECTOR PRE-
VDCR VDCIR PORT
AMPLIFIER
KEYBOARD
FINGER PROBE
SEPARATOR
2500 S
OF
SAMPLE
HOLD
SUBTRACTOR FILTER AC & DC MULTIPLIER
ADC
&
IR COMPONENT
IR CHANNEL VACIR
RED LED ON
BOTH LEDs OFF
IR LED ON
BLOCK DIAGRAM
BOTH LEDs OFF
625 S
TIMING SEQUENCE

9. Pulse Oximeter
SPECIFICATIONS :
Measurement Range:
Oxygen Saturation (SaO2) : 40-100%
Pulse Rate (BPM) : 30-240 bpm
Accuracy:
Oxygen Saturation (SaO2) : ±2 Digits
Pulse Rate (BPM) : ±3 Digits
Resolution:
Oxygen Saturation (SaO2) : 1%
Pulse Rate (BPM) : 1BPM
Display:
Two Three digit red seven segment display for oxygen saturation and pulse rate.
Ten segment bar graph display for pulse amplitude.
Sensor Compatibility:
DS-100A : Nellcor Dura sensor for Adult
Wavelength : 660nm (RED), 940nm (IR)

10. Pulse Oximeter
SPECIFICATIONS :
Alarms and Indication:
 Alarm for high and low SaO2 percentage.
 Alarm for high and low Pulse Rate.
 Beep sound with each detected pulse when a sensor’s derived signal is
present.
 Visual indication if sensor accidentally slipped from finger.
 RS232 PC interface for data downloading and displaying Plethysmographic
signal.
 Battery Low warning and alarms.
Trend facility:
Store the trend data upto 100 patients and 24Hrs of run time.
With Trend Analysis Software.
Electrical Specification:
Mains Voltage : 230V AC, 50Hz
Power Consumption : Less than 1 watt
Battery Backup : Inbuilt rechargeable Lead Acid
battery of 6V/3.2AH With 16 hrs
backup at full charge

11. Pulse Oximeter
Lab. & Clinical Trials
We have tested and calibrated the system by using BIO-
TEK SpO2 simulator in the whole range of SaO2 and
Pulse Rate and then taken to Deptt. of
Anaesthesia, PGI, Chandigarh for its clinical trials on
patients. The results of the system were compared with
Datex Ohmeda (PGI) System and found satisfactory as
per our specifications.

15. Pulse Oximeter
Know-how transferred & Status :
The know-how of Pulse Oximeter was transferred to
M/s Pranavam Life Care Instruments (P) Ltd, Ernakulam & in
production

16. DIFFERENT AVAILABLE MODELS OF PULSE OXIMETER
BCI
BIG SIZE SMALL SIZE FINGER TYPE
PRICE: US $1395.00 PRICE: US $1095.00 PRICE: $279.95
PRICE: RS 69750 PRICE: RS 54750 PRICE: RS 13975
HANDHELD SIZE
PRICE: US $ 695.00
PRICE: RS 34750

17. DIFFERENT AVAILABLE MODELS OF PULSE OXIMETER
NELLCOR
BIG SIZE HANDHELD SIZE
OHMEDA
BIG SIZE BIG SIZE + PRINTER HANDHELD SIZE

19. Pulse Oximeter
Flow chart for calculation of SaO2