|
Upload | Sign in |
|---|
A pulse oximeter is a device intended for the non-invasive measurement of arterial blood oxygen saturation and pulse rate.
Pulse oximetry is a non-invasive method allowing the monitoring of the saturation of a patient's hemoglobin.
It's based on measuring the difference between levels of the red pigment hemoglobin which carries oxygen in your blood. It turns out that oxygenated hemoglobin ("oxyhemoglobin") and nonoxygenated hemoglobin ("deoxyhemoglobin") in your blood are different colors.
In transmissive pulse oximetry, a sensor is placed on a thin part of the patient's body, usually a fingertip . Light of two different wavelengths is passed through the patient to a photodetector.
The changing absorbance at each of the wavelengths is measured, allowing determination of the absorbances due to the pulsing arterial blood.
Reflectance pulse oximetry may be used as an alternative to transmissive pulse oximetery.
This method does not require a thin section of the patient's body and is therefore well suited to more universal application such as the feet, forehead and chest, but it also has some limitations. Vasodilation and pooling of venous blood in the head due to compromised venous return to the heart, as occurs with congenital cyanotic heart disease patients, can cause a combination of arterial and venous pulsations in the forehead region and lead to spurious SpO2 (Saturation of peripheral oxygen) results.
How does a Pulse Oximeter work:
The measurements are obtained by simply shining two wavelengths of light (1 is a visible red beam, the other an invisible infrared beam) at the fingertip. By measuring how much light has been absorbed by the oxygen in the blood, an oxygen saturation reading is established and displayed as a percentage of the maximum amount of oxygen the blood could carry.
The oximeter looks for minute changes in absorption as the blood is pumped past the measurement site by the beating of the heart, so selecting somewhere with strong pulse is important. A weak pulse or restricted blood flow may limit the oximeter’s ability to obtain accurate measurements.
In the same way, introducing false pulses of blood, such as extreme movement of the measurement site, could equally affect the oximeter’s performance. It is important to understand what the oximeter is doing to ensure you get the best out of your oximeter.
The chief advantages of pulse oximeter over other methodologies are cost and speed.