2024 Author: Josephine Shorter | [email protected]. Last modified: 2024-01-07 17:49
Pulse oximetry: pros and cons
A sufficient amount of oxygen in the blood is an indicator that the body is not suffering from hypoxia. In order to determine its level, it is necessary to know the number of erythrocytes 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, which are permeated with many capillaries. They absorb it and carry it with the bloodstream throughout the body to various organs and tissues. Oxygen is carried by red blood cells called erythrocytes.
Inside the erythrocytes there are hemoglobin molecules that can transport 4 oxygen particles on them. Saturation is the average percentage of saturation of red blood cells with oxygen molecules. This concept is often appealed to by anesthesiologists, who assess the well-being of a patient under anesthesia precisely 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 index of 95% is sufficient. In this case, tissues and organs will not suffer from hypoxia.
Sometimes the saturation percentage decreases, which indicates pathological processes in the body. This fact cannot be ignored. A device called a pulse oximeter is used to monitor the oxygen saturation of arterial blood.
Content:
- How does pulse oximetry work?
- Where and when is pulse oximetry used?
- Pulse oximetry during sleep
- Saturation: norm and pathology
How does pulse oximetry work?
A 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 work of a pulse oximeter is based.
The red and infrared wave comes out of the light source located on the device. The blood absorbs these waves with the force with which the oxygen-carrying hemoglobin molecules allow it. 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 has not been absorbed enters the detector. The device performs 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 arterial blood, a few seconds are enough (no more than 20).
At this point in time, doctors use transmission and reflected pulse oximetry:
- Transmission pulse oximetry. The sensor and light emitter are located 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 are not absorbed by hemoglobin, but those that are reflected from 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. Thus, the device changes its operation if the study is carried out in bright light, or the sensor is installed on an object in motion. The varnish applied to the nail plate can affect the accuracy of the study if the device is put on the finger. In addition, if the pulse oximeter is installed incorrectly, then certain errors in the readings are possible. Conditions such as shock and hypovolemia in a patient can affect the accuracy of the data. In case of carbon monoxide poisoning, the saturation level can be equated to 100%, and the blood at this time will be saturated not with oxygen, but with carbon dioxide.
Where and when is pulse oximetry used?
If without food and water the human body is able to exist for a relatively long period of time, since it has their reserves, then without oxygen it simply cannot live. Already a few minutes after the start of acute oxygen starvation, processes are launched in the body that lead to its death. First of all, the organs responsible for the vital activity of the body suffer.
If hypoxia proceeds in a chronic form, then all organs and systems will suffer. This will certainly affect the well-being of a person. He has more frequent headaches, dizziness appears, drowsiness increases, attention and memory suffer. Arrhythmia may occur, and the likelihood of heart attack and hypertension increases.
Most specialists always have a tonometer and a stethoscope in their office, but they do not have a pulse oximeter, which makes it impossible to determine the patient's saturation level. While this indicator is of no small importance in the treatment and diagnosis of patients with diseases of the blood, respiratory and cardiovascular systems. In European countries, where the level of medicine reaches a high level, a pulse oximeter is always available from doctors such as a therapist, cardiologist, pulmonologist.
In Russia, pulse oximetry is a research method that is available only in an intensive care unit. He is prescribed to patients who are on the verge of life and death. The fact is that such a device is expensive, and the majority of domestic doctors have little awareness of its diagnostic value.
If a person is under anesthesia, or transportation of a patient who is in serious condition is required, pulse oximetry is mandatory. Therefore, in the practice of anesthesiologists and resuscitators, this study is widespread.
Regular monitoring of the oxygen content in the blood is required for premature babies during the neonatal period. Hypoxia that develops in such babies can lead to severe damage to the organs of vision.
Therapists are also armed with this method. It is used to diagnose diseases of the respiratory system, with complaints of patients with apnea, with various chronic pathologies.
The indications for performing pulse oximetry are as follows:
- The need for oxygen therapy.
- Respiratory failure of various etiologies.
- Conducting anesthesia.
- The recovery period after undergoing vascular surgery or orthopedic surgery.
- Severe hypoxia, accompanied by disturbances in the work of internal organs.
- Chronic nocturnal hypoxemia.
- Apnea.
Pulse oximetry during sleep
Sometimes it is required to determine the level of oxygen in the blood at night. In some cases, respiratory arrest and hypoxia occurs precisely at night. A sleeping person often does not even suspect that during sleep he has hypoxia, which can pose a direct threat not only to health, but also to life. Apnea affects people who are overweight, with diseases of the thyroid gland, respiratory system, and high blood pressure.
Symptoms that indicate the need for nocturnal pulse oximetry are: snoring while sleeping, poor sleep quality, daytime sleepiness, heart problems, frequent headaches. To determine the presence or absence of hypoxia, it is necessary to measure the level of oxygen in the blood during a night's rest.
For the study, the patient is put on the device for the whole night. For several hours it will record oxygen saturation, pulse and pulse wave. It is possible to determine the readings up to 30 thousand times in one night alone.
In this case, there is no need for the subject to be in the hospital. If there is no direct threat to life and health, then the study can be carried out at home.
The procedure is carried out as follows:
- The sensor is put on the finger, and the sensing device is fixed on the wrist. The device turns on automatically.
- During the night, the pulse oximeter remains on the person's hand. They record every moment of his awakening.
- Urom the device should be removed, and the device should be returned to the doctor. The doctor will analyze the data obtained.
The information received from the device in the period from 22:00 to 8:00 is subject to study. In this case, a person should be in a comfortable environment for him. The air temperature in the bedroom should not exceed 23 ° C. You can not drink tonic drinks in the evening, you should refuse to take any medications. If a person wakes up at night, he has a headache, or he was taking any drug, the doctor should be informed about this. If the saturation level during sleep fell below 88%, then the person needs night oxygen therapy.
Who needs to perform nighttime pulse oximetry:
- Overweight people, provided that they have reached the second degree of obesity.
- Patients with obstructive lesions of the respiratory system.
- Hypertensive patients and people with second degree heart failure.
- Patients with myxedema.
Even if none of the above diagnoses has yet been made, this does not mean that pulse oximetry cannot be performed. The study must be performed if there are indications for it in the form of pathological symptoms. Particular attention should be paid to such signs of pathology as: night snoring, respiratory arrest during sleep, increased sweating, frequent awakenings, excessive daytime sleepiness, frequent headaches, shortness of breath appearing at night.
Saturation: norm and pathology
The normal level of saturation in the blood of a person, regardless of his age, equates to 95-98% for arterial blood and within 75% for venous blood. If this indicator is lower, then the person develops hypoxia. During oxygen therapy, the oxygen level in the blood will be increased to 100%.
If the saturation is 95% or less, then the person needs treatment, which should be prescribed immediately. With a saturation of 90%, emergency assistance to the patient is required. Most often, when the indicator drops below 90%, the device starts to emit a sound signal. It can also be heard with a slow pulse, with its complete disappearance or with tachycardia.
Saturation is measured in arterial blood, since it is this blood that carries oxygen from the lungs to the tissues. Venous blood in this regard is not of diagnostic value. If the patient has an arterial spasm, or the amount of blood in the body is reduced, then the device may give false information.
Normal heart rate values for an adult who is at rest range from 60-90 beats per minute. In children, this indicator differs depending on their age. For newborns, the norm is 140 beats per minute, and as the child grows up, this figure decreases. By adolescence, the heart rate should be equal to the normal values for an adult.
Stationary pulse oximeters are used for research in a hospital setting. They are equipped with sensors and can store a large amount of various information.
Portable pulse oximeters, which are fixed on the finger, are the most mobile. They do not take up much space, are easy to use and easy to handle. Such devices can be used at home. There are also belt pulse oximeters.
People suffering from respiratory failure, which develops against the background of diseases of the cardiovascular or pulmonary system, receive a wide variety of treatments. However, almost all of them need long-term oxygen therapy, which they are not prescribed.
Pulse oximetry is not performed on patients with chronic diseases, not only because of the lack of the necessary equipment. Often, doctors consider the condition of such patients stable enough to direct them to any additional diagnostic or therapeutic measures.
If pulse oximetry was carried out, hypoxia would have been unambiguously detected in most of these patients, which is the basis for the appointment of oxygen therapy. Of course, this method of treatment is not a salvation from illness, but oxygen therapy is quite capable of prolonging the life of patients with chronic respiratory failure and reducing the risk of death in sleep on the background of apnea.
Almost every person has such a device as a tonometer. This allows you to diagnose and prevent complications of hypertension. If pulse oximeters had the same prevalence, then much fewer people would suffer from the effects of hypoxia.
It should be understood that pulse oximetry is the most important study, which in its importance is not inferior to the measurement of pressure or pulse. With the timely appointment of oxygen therapy, it is possible to improve the patient's quality of life, 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. Cessation of breathing during sleep, 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 studies to which people who are overweight are sent. This makes it possible to prescribe oxygen therapy for them in time and prevent respiratory arrest during sleep.
Medicine is constantly developing and improving. In many countries, a pulse oximeter can already be found in most homes. In Russia, this research is only gaining momentum. However, we 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 a glucometer, thermometer or tonometer.
Author of the article: Alekseeva Maria Yurievna | Therapist
Education: From 2010 to 2016 Practitioner of the therapeutic hospital of the central medical-sanitary unit No. 21, city of elektrostal. Since 2016 she has been working in the diagnostic center No. 3.
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