Pulse Oximeters - Basics
| What does “Pulse Oximeter” mean? |
Pulse = the changes in arterial blood with every heart beat Oxi = oxygen Meter = measurement Pulse oximeter = device to measure the rate and the amount of oxygen in the beating arterial blood |
| What does it do? |
The pulse oximeter measures the amount of oxygen in the arterial
blood. It measures the amount of oxygen as a percentage of haemoglobin molecules that are oxygenated versus the total amount of haemoglobin molecules. Most Pulse Oximeters also display Pulse (Heart) Rate. |
| Physiology | Haemoglobin is a protein in red blood cells. When oxygen enters
the blood it is picked up by the haemoglobin and carried around the body attached to the haemoglobin. Haemoglobin with oxygen attached to it is called Oxyhaemoglobin. |
How it works |
A pulse oximeter probe consists of: - 2 low power LEDs: Infra Red 940 nm & Red 660 nm - One photodetector The infrared and red light is shone alternatively through some tissue (finger, foot, toe, earlobe or nose). As the light is passed through the tissue some of it is absorbed. The amount of light absorbed changes every time the heart beats as the blood pulses past the sensor. The light is absorbed differently by haemoglobin and oxyhaemoglobin. The light intensity of the infrared and red light is measured by the photodetector after it has passed through the finger. The pulse oximeter calculates the percentage of haemoglobin which it oxygenated. SpO2 = Oxyhaemoglobin x 100 % Total Haemoglobin The time interval between 4 – 8 Heart Beats is measured and from that a Pulse (or Heart) Rate is calculated and displayed. |
| Units of measurement |
SpO2: %, Pulse rate: Beats Per Minute |
| Typical values |
Adults 95 – 100 % 50 – 90 BPM Neonates 90 – 98 % 120 – 180 BPM |
| Picture of equipment |
|
 Datex TuffSat Pulse Oximeter |