Pulse Oximeter
A non-invasive device that estimates blood oxygen saturation (SpO2) and pulse rate using light absorption through tissue.
Objective
Learn pulse oximetry fundamentals including SpO2 measurement, photoplethysmography principles, and clinical interpretation of oxygen saturation readings.
Learning Outcomes
- Understand Beer-Lambert law applications
- Demonstrate proper sensor placement
- Interpret SpO2 and pulse rate measurements
- Recognize factors affecting measurement accuracy
Key Principles
Beer-Lambert Law
The amount of light absorbed by a solution is proportional to the concentration of the absorbing substance and path length through it.
Dual Wavelength Detection
Red light (660 nm) and infrared light (940 nm) are used because oxyhaemoglobin and deoxyhaemoglobin absorb these wavelengths differently.
Photoplethysmography (PPG)
Volume changes in blood vessels caused by each heartbeat modulate the transmitted light signal, enabling both SpO₂ and pulse rate measurement.
Normal Ranges
Healthy SpO₂: 95–100%. Pulse rate: 60–100 bpm. Perfusion index > 1.0% indicates good circulation.
Equipment Familiarization
Click on each piece of equipment to learn about it. Explore ALL items before proceeding.
Equipment Explorer
Click on an item to see details on the right
Pulse Oximeter Device
Main monitoring unit with display and processing
Sensor Probe
Finger clip sensor with LED and photodetector
LED Light Sources
Red (660nm) and infrared (940nm) LEDs
Photodetector
Measures transmitted light intensity
Component Details
Select an equipment item on the left to view its detailed information and illustration here.
Pulse Oximetry Principles
Beer-Lambert Law
Pulse oximetry relies on the differential absorption of red and infrared light by oxygenated and deoxygenated hemoglobin.
SpO2 = f(R)
where R = (ACred/DCred) / (ACIR/DCIR)
Key Concepts
- SpO2: Peripheral oxygen saturation (95-100% normal)
- Pulse Rate: Heart rate derived from pulsatile signal
- Perfusion Index: Strength of peripheral circulation
- Plethysmograph: Waveform showing pulsatile flow
Device Setup & Sensor Attachment
Clean the sensor, then attach it with correct alignment for reliable readings
Guided Setup Assistant
Let's get started! Follow one action at a time.
Swipe to clean sensor
Drag clip to fingertip
Hold for signal verify
1
Clean
2
Attach
3
Verify
Oximeter Clip (Left Side)
--
Cleaning Cloth
Step 1: Hold and move the cloth into the highlighted zone to wipe.
Target Finger (Right Side)
Cleaning Progress
0%
Use the cloth to wipe over the highlighted sensor zone until 100%.
Alignment Score
0%
Setup Progress
0 / 3 complete
Perfect placement! Setup Star
Step-by-Step Setup Process
Complete each step to unlock monitoring
1. Power On Device
Turn on the pulse oximeter and wait for the display to show "--" (ready state)
Why: Device initializes LEDs, detector, and display.
Completed
2. Clean Sensor Surface
Swipe the highlighted zone until the bar reaches 100%.
Why: Prevents contamination and improves contact/accuracy.
Wipe the sensor zone
3. Attach Sensor to Finger
Drag clip to fingertip. Green score (≥ 60%) means perfect fit.
Tip: Center the LEDs and detector across the finger.
Waiting for attachment
4. Verify Signal Quality
Hold position and wait for “Good Signal”.
Success: Stable SpO2 and pulse rate appear.
Complete step 3 first
Real-Time Device Status
Monitor connection and signal quality
Connection
DisconnectedSensor
Not AttachedSignal Quality
No SignalStep 3
Patient Monitoring
Record SpO2, pulse rate, and observe the photoplethysmographic waveform
Pulse Oximeter Display
SpO2
--
%
Pulse
--
bpm
PI:
-.-
%
Signal:
Plethysmographic Waveform
Patient Condition
Healthy Adult
Normal SpO2: 98-100%
Pulse: 60-100 bpm
Mild Hypoxia
SpO2: 90-95%
Slightly elevated pulse
Moderate Hypoxia
SpO2: 85-90%
Compensatory tachycardia
Poor Circulation
Low perfusion index
Weak signal quality
Measurement Log
Time
SpO2
Pulse
PI
Condition
Step 4
Analysis & Results
Interpret the measurements and understand clinical significance
Measurement Summary
Average SpO2
--
%
Average Pulse
--
bpm
Average PI
--
%
Measurements
0
total
Clinical Interpretation
SpO2 Assessment
Record measurements to see assessment
Pulse Rate Assessment
Record measurements to see assessment
Perfusion Assessment
Record measurements to see assessment
Reference Values
Parameter
Normal Range
Critical Values
SpO2
95-100%
< 90%
Pulse Rate
60-100 bpm
< 50 or > 150
Perfusion Index
> 1.0%
< 0.5%
Clinical Notes
- SpO2 < 90% indicates significant hypoxemia
- Motion artifacts can cause false readings
- Poor perfusion affects accuracy
- Nail polish may interfere with measurements
- Carbon monoxide poisoning shows false normal readings
Lab Report
Experiment Summary
This pulse oximetry lab demonstrated the principles of non-invasive oxygen saturation monitoring using photoplethysmography.
Key Learning Objectives
Performance Metrics
Equipment Explored
0/4
Setup Completed
0/4
Measurements Taken
0