A sufficient amount of oxygen in the blood is an indicator that the body does not suffer from hypoxia. In order to determine its level, it is necessary to know the number of red blood cells in the blood. For this purpose, a study is carried out, which is called pulse oximetry.
The air that a person breathes enters the lungs, penetrated by many capillaries. They absorb it and carry it through the body with the bloodstream to various organs and tissues. Oxygen carriers are red blood cells called erythrocytes.
Red blood cells contain hemoglobin molecules that can carry 4 particles of oxygen. Saturation is the average percentage of saturation of red blood cells with oxygen molecules. This concept is often appealed by anesthesiologists, who assess the well-being of a patient under anesthesia by saturation.
If hemoglobin carries 4 oxygen molecules at once, then the saturation level is 100%. However, in order for a person to feel good, a saturation indicator of 95% is enough. In this case, tissues and organs will not suffer from hypoxia.
Sometimes the percentage of saturation decreases, which indicates pathological processes occurring in the body. This fact cannot be ignored. A device called a pulse oximeter is used to monitor arterial oxygen saturation.
How does the pulse oximetry method work?
The pulse oximeter consists of a light source, sensors, a detector and a processor that analyzes the received data. The wavelength of light that hemoglobin can absorb varies depending on how much oxygen it contains. It is on this principle that the operation of a pulse oximeter is based.
The red and infrared wave comes out of the light source located on the device. Blood absorbs these waves with the force with which it is allowed to do so by hemoglobin molecules that carry oxygen. Hemoglobin, which has already attached an oxygen molecule to itself, will absorb infrared light. Hemoglobin, which does not contain an oxygen molecule, absorbs red light. The amount of light that remains unabsorbed falls on the detector. The device performs the analysis and displays the result on the monitor screen. This method does not require invasive intervention, it does not cause pain or other discomfort to the patient. In order to assess the level of oxygen in the arterial blood, a few seconds (no more than 20) are enough.
At the moment, doctors use transmission and reflected pulse oximetry:
Transmission pulse oximetry. The sensor and the light emitter are placed on both sides of the tissue under study. Most often, a person’s finger, nose or ear is used for this purpose.
Reflected pulse oximetry. The device registers those waves that hemoglobin does not absorb, but those that are reflected from the tissues. Therefore, the sensors can be placed anywhere on the body. The possibilities of using this method are somewhat expanded, but the accuracy of the study is the same in both cases.
However, pulse oximetry has several disadvantages. So, the device changes operation if the study is carried out in bright light, or the sensor is installed on an object that is in motion. The varnish applied to the nail plate can affect the accuracy of the study if the device is put on a finger. In addition, if the pulse oximeter is installed incorrectly, certain errors in the readings are possible. Conditions such as shock and hypovolemia in the patient can affect the accuracy of the data. In case of carbon monoxide poisoning, the saturation level can be equal to 100%, and the blood at this time will be saturated not with oxygen, but with carbon dioxide.
[Video] Technical explanation of how pulse oximetry works:
Almost every person has such a device as a tonometer in the house. This allows diagnosing and preventing complications of hypertension. If pulse oximeters had the same prevalence, then far fewer people would suffer from the effects of hypoxia.
It should be understood that pulse oximetry is the most important study, which in its significance is not inferior to measuring pressure or pulse. With the timely appointment of oxygen therapy, it is possible to improve the quality of life of the patient, increase its duration and reduce the likelihood of serious complications.
Obese people should definitely think about pulse oximetry. Almost all patients with the second stage of obesity have hypoxia. Stopping breathing in a dream, which leads to the death of a person, often comes as a complete surprise to loved ones. In foreign clinics, nighttime pulse oximetry is one of the most common tests for overweight people. This makes it possible to prescribe oxygen therapy to them in time and prevent respiratory arrest during sleep.
Medicine is constantly evolving and improving. In many countries, a pulse oximeter can already be found in most homes. In Russia, this research is only gaining momentum. However, one can hope that in the coming years, pulse oximetry will be available to everyone, and the device itself for measuring the level of oxygen in the blood will not be surprising, such as, for example, a glucometer, thermometer or tonometer.