How to measure blood oxygen

Maintaining a normal blood oxygen level is critical to maintaining the metabolic functions of the body on a daily basis. Oxygen, as you know, is essential to life and when cells are deprived of oxygen, they will eventually die.

Explaining the Oxygen Delivery System

Oxygen is taken in from the air through the mouth and nose and drawn into the lungs. Capillaries surround the bronchial tubes inside the lungs. Oxygen diffuses into the blood vessels, and attaches to the red blood cell, which transports the chemical to cells throughout the body. Cells use oxygen to create a molecule called ATP, which is energy needed for metabolism and other cellular processes.

How is Blood Oxygen Measured?

Oxygen saturation is measured by a pulse oximeter, a device placed on the finger that uses light absorption to indicate the level of saturated hemoglobin, the protein on the red blood cell that stores oxygen during transport. Oxygen levels can also be determined through a blood test called an arterial blood gas, or ABG. This test measures the partial pressure of many blood gasses, including oxygen.

Normal Blood Oxygen Levels

Healthy people have a normal range of oxygen saturation from 95% – 100%, although levels down to 90% are common and not usually cause for alarm. During exercise, the increased oxygen consumption may reduce blood saturation, but the increased breathing rate and blood flow compensate for this. Oxygen levels remain within the established normal range.

Low Oxygen Blood Levels (Hypoxemia)

Hypoxemia is the condition of not having enough oxygen in the blood. Causes of hypoxemia include low inspired oxygen levels, alveolar hypoventilation, ventilation-perfusion inequality, and impairment of the oxygen diffusion across the cell membrane. Ventilation-perfusion inequality is a common cause of hypoxemia in people with lung disease such as COPD, emphysema, sleep apnea, acute respiratory distress syndrome, asthma, or interstitial lung disease. It can also occur with cardiac problems, such as congenital heart disease and low cardiac output, where the heart does not adequately pump blood throughout the body.

Cigarette smoking can also cause low blood oxygen levels even without the presence of a lung condition. Cigarette smoke contains carbon monoxide, which competes with oxygen on the hemoglobin of the red blood cell. Because hemoglobin saturated with CO (carbon monoxide) can not be differentiated from that with oxygen, a pulse oximetry test may indicate the blood level is normal, when in fact the oxygen levels are low.

Normal and Abnormal Blood Oxygen Levels During Sleep

How to measure blood oxygen

Low sleep apnea oxygen level is a sign that your treatment for sleep apnea is not effective.

Patients with breathing problems during sleep (sleep apnea, COPD) often have low oxygen levels in their blood.

Keep in mind that anything below 90% oxygen level is dangerous to your body and require intervention. Another thing to consider is that the brain can only survive 4 minutes once oxygen is completely cut off.

In this page you’ll learn:

  • What should your oxygen level be during sleep,
  • How sleep apnea affects the oxygen levels in your blood,
  • How oxygen levels affect your body,
  • The link between pregnancy and low oxygen levels in obese women,
  • How to monitor oxygen saturation levels,
  • What is the best finger oximeter to monitor blood oxygen levels,
  • How to treat sleep apnea oxygen level.

Oxygen Levels During Sleep Apnea

In sleep, the upper airway muscle tone of the patients with sleep apnea tends to narrow and collapses temporarily. When this happens, the breathing stops accompanied by a drop in blood oxygen levels and arousal from sleep.

The low oxygen levels during sleep can make you feel very tired in the morning and will contribute to more restless sleep.

Furthermore, when the oxygen levels start to drop, the carbon dioxide levels build up in your blood. This can lead to morning headaches, fatigue and sleepiness during the day.

Scientific Proofs – Oxygen Levels Decreases During Apneas

Even the most recent studies (2012) demonstrates the link between sleep apnea and oxygen desaturation. That’s why the oximeter is an important tool in clinical assessment.

With a finger pulse oximeter you can monitor yourself to see how effective is CPAP (you’ll learn how to do this bellow). The device can also be used to diagnose sleep apnea, but only if you use a quality product.

For more information on how to use an oximeter to diagnose sleep apnea, read the portable pulse oximeter article.

How Does Sleep Apnea Oxygen Level Affect the Body?

Any value of blood oxygen level bellow 92% is abnormal. However, the number of desaturations and the time spent with abnormal oxygen levels is important.

For example, if you only desaturated below 92% once or twice during a 7 hour sleep, and the desaturation level lasted only a couple of seconds, it’s not a reason for worry.

Your body will be seriously affected when you’ll have long term low oxygen levels. This can lead to:

  • heart rhythm problems,
  • increasing pressure on the right side of the heart,
  • fluid build up in the body,
  • heart failure,
  • stroke.

Increasing the pressure on the right side of the heart

The right side of the heart has the role of pumping blood through the lungs, which requires a much lower pressure.

A higher pressure can lead to severe fluid buildup in the body that can cause life-threatening shortness of breath, heart failure and even death.

Please call your doctor urgently if you experience chest pain or shortness of breath that is not relieved by rest.

Monitoring Your Blood Oxygen Levels

If your doctor discovers that your blood oxygen level (oxygen saturation) is less than about 90% during the day (when you are resting), then your oxygen levels are probably dropping during the night. This means that you have sleep apnea, or other respiratory disorders, like UARS.

Your doctor may recommend overnight monitoring of your oxygen levels using am oximeter. In a sleep study, you usually have the oximeter attached on the finger.

You can use a portable oxygen saturation monitor or oximeter, a cool little device that can record your sleep apnea oxygen level and pulse rate during sleep. A medical approved oximeter is truly a great tool to see how well CPAP is working for you.

A tip before buying an oximeter: you would do well to invest in a recording oximeter with software . You can upload your data in a computer, and you can go to your sleep specialist with the results.

See an example in the followingvideo:

For more info about sleep study for sleep apnea, see sleep studies.

So, if you have a low blood oxygen level, follow up with the sleep study as soon as possible.

Continued drops in O2 levels will cause damage to cognitive function, short term memory, stroke and heart attack in your sleep, and a host of other problems.

Oxygen Levels in Pregnant Women

Overweight women who are pregnant or women who gain too much weight during pregnancy are at a higher risk of developing sleep apnea. This can cause a drop in blodd oxygen levels during sleep which can create complications for the baby.

So if you are overweight or gained a lot of weight during pregnancy, speak with your doctor to investigate if you have sleep apnea.

For more info about obesity, see sleep apnea and obesity.

Improving Sleep Apnea Oxygen Level

Patients with sleep apnea are usually treated with CPAP machines. If apnea episodes disappear, the oxygen levels will improve to normal levels.

How often should you use the CPAP?

If your doctor prescribed CPAP therapy, you should NEVER go a night EVER without a CPAP on or even take a nap without one.

More strategies to treat sleep apnea:

If your oxygen saturations drop significantly and persist during the night, you may benefit from overnight oxygen delivered by nasal masks or nasal prongs.

CPAP and Oxygen Levels During Sleep

You can have low oxygen levels during sleep even if you use the CPAP. This means that your CPAP doesn’t have the desired effect.

That’s why is important to monitor your oxygen and pulse rate.

To keep a better eye on your sleep apnea oxygen level you might consider purchasing a finger pulse oximeter.

Remember: don’t use inferior equipment to measure your well-being and don’t change anything without checking that information with a second opinion or proper equipment.

Oxygen levels in the blood are tested to examine several functions of the human body. A dip in blood oxygen levels, is an indication of an underlying disorder. This article explains what these fluctuations mean, and also defines normal blood oxygen levels.

How to measure blood oxygen

Oxygen levels in the blood are tested to examine several functions of the human body. A dip in blood oxygen levels, is an indication of an underlying disorder. This article explains what these fluctuations mean, and also defines normal blood oxygen levels.

Oxygen is a basic requirement for sustenance of life. The normal blood oxygen levels are a measurement of the saturation of oxygen in the blood. The red blood cells contain a molecule known as hemoglobin that binds to the atmospheric oxygen, and carries it to different parts of the body. When there is any kind of variation in the levels of oxygen in the blood, it can lead to health complications. Given below are details pertaining to normal levels of oxygen in the blood, and what the variations signify.

What Are Normal Levels of Oxygen in Blood?

  • In most cases, an oxygen level that hovers around 95 to 100% is considered healthy.
  • Any reading below 90% is a cause of concern, which needs to be investigated by a doctor.

Levels of oxygen in the body can be measured with the help of various methods. The most common way of determining whether oxygen saturation levels are healthy, is with the help of a blood test used to check the arterial blood gas. Another convenient way of checking the level of oxygen in the blood, is by using a pulse oximeter. This is a small device that measures the levels of oxygen in the blood by means of a light sensor.

Hypoxemia: Low Levels of Oxygen

Hypoxemia occurs when the oxygen level in the blood dips below 90%. When this happens, the person experiences immediate shortness of breath, as the body tries to elevate the level of oxygen in the body.

Causes

  • Anemia
  • Chronic Obstructive Pulmonary Disease (COPD)
  • Emphysema
  • Pneumonia
  • Pneumothorax
  • Acute Respiratory Distress Syndrome (ARDS)
  • Pulmonary embolism
  • Pulmonary fibrosis
  • Sleep apnea

If you frequently experience difficulty in breathing, especially after any minor physical activity, it is necessary to get yourself examined. Shortness of breath and choking while sleeping, are symptoms of sleep apnea, which also needs medical attention.

Precautionary Measures

  • Breathing problems are aggravated by smoking, so ensure that you cut down on it, if you have this habit.
  • Passive smoking is also known to cause shortness of breath in many.
  • Follow a lifestyle that involves healthy eating, coupled with exercise routines.
  • Learn breathing exercises to allow oxygen levels to remain normal.

Hyperoxia: High Levels of Oxygen

Hyperoxia is a condition characterized by very high levels of oxygen in the blood. This generally occurs as a result of breathing concentrated oxygen. Considered to be a serious condition, it can lead to cell death and damage, mostly in the central nervous system, eyes, and lungs.

People who are susceptible to this condition include scuba divers, as they are exposed to high atmospheric pressure, those sent on human space missions, and those who are undergoing hyperbaric oxygen therapy.

Symptoms of hyperoxia include disorientation, breathing problems, and disturbed vision. In cases where oxygen intoxication is very high, there could be oxidative damage to the cells, deflation of alveoli in the lungs, retinal detachment, and seizures. This kind of toxicity can be managed by reducing exposure to elevated levels of oxygen.

To prevent the occurrence of the symptoms, those having to breathe concentrated levels of oxygen are made to undergo rigorous training regarding the use of oxygen cylinders/spacesuits under varying atmospheric pressures.

Oxygen saturation levels are an important parameter used for checking the presence of any lung disease or abnormalities in the level of hemoglobin in the blood. It is important to ensure that oxygen levels in the blood fall within the ideal range, as any kind of deprivation of oxygen to the body, even for a small time span, can lead to irreversible damage to body’s organs.

This article was medically reviewed by Tapan Abrol, MD. Dr. Abrol is a Movement Disorders and Neurology Fellow at the Icahn School of Medicine in New York. He completed his MD at the Acharya Shri Chander College of Medical Sciences & Hospital and finished his residency in Neurology at the University of Louisville in 2017. He is a member of the American Board of Psychiatry and Neurology.

There are 10 references cited in this article, which can be found at the bottom of the page.

This article has been viewed 121,597 times.

Experts say that your doctor might measure your blood oxygen levels to make sure your lungs are working correctly, to make sure a medical treatment is working, to check for sleep apnea, or to find out if you’re healthy enough for exercise. [1] X Trustworthy Source Johns Hopkins Medicine Official resource database of the world-leading Johns Hopkins Hospital Go to source Your doctor may do an arterial blood gas test or pulse oximetry test to measure how much oxygen is in your blood. Research shows that blood oxygen tests won’t diagnose your condition, but they can help your doctor narrow down the cause of your symptoms. [2] X Trustworthy Source MedlinePlus Collection of medical information sourced from the US National Library of Medicine Go to source While arterial blood gas tests are typically more accurate, pulse oximetry may show your blood oxygen levels over a period of time. [3] X Research source Fortunately, these tests are simple and easy.

A blood oxygen level test, also known as a blood gas analysis, measures the amount of oxygen and carbon dioxide in the blood. When you breathe, your lungs take in (inhale) oxygen and breathe out (exhale) carbon dioxide. If there is an imbalance in the oxygen and carbon dioxide levels in your blood, it can mean your lungs aren’t working well.

A blood oxygen level test also checks the balance of acids and bases, known as pH balance, in the blood. Too much or too little acid in the blood can mean there is a problem with your lungs or kidneys.

Other names: blood gas test, arterial blood gases, ABG, blood gas analysis, oxygen saturation test

What is it used for?

A blood oxygen level test is used to check how well your lungs are working and measure the acid-base balance in your blood. The test usually includes the following measurements:

  • Oxygen content (O2CT). This measures the amount of oxygen in the blood.
  • Oxygen saturation (O2Sat). This measures the amount of hemoglobin in your blood. Hemoglobin is a protein in your red blood cells that carries oxygen from your lungs to the rest of your body.
  • Partial pressure of oxygen (PaO2). This measures the pressure of oxygen dissolved in the blood. It helps show how well oxygen moves from your lungs to your bloodstream.
  • Partial pressure of carbon dioxide (PaCO2). This measures the amount of carbon dioxide in the blood.
  • pH. This measures the balance of acids and bases in the blood.

Why do I need a blood oxygen level test?

There are many reasons this test is ordered. You may need a blood oxygen level test if you:

  • Have trouble breathing
  • Have frequent periods of nausea and/or vomiting
  • Are being treated for a lung disease, such as asthma, chronic obstructive pulmonary disease (COPD), or cystic fibrosis. The test can help to see if treatment is working.
  • Recently injured your head or neck, which can affect your breathing
  • Had a drug overdose
  • Are receiving oxygen therapy while in the hospital. The test can help make sure you are getting the right amount of oxygen.
  • Have carbon monoxide poisoning
  • Have a smoke inhalation injury

A newborn baby may also need this test if he or she is having trouble breathing.

What happens during a blood oxygen level test?

Most blood tests take a sample from a vein. For this test, a health care provider will take a sample of blood from an artery. That’s because blood from an artery has higher oxygen levels than blood from a vein. The sample is usually taken from an artery inside the wrist. This is called the radial artery. Sometimes the sample is taken from an artery in the elbow or the groin. If a newborn is being tested, the sample may be taken from the baby’s heel or umbilical cord.

During the procedure, your provider will insert a needle with a syringe into the artery. You may feel a sharp pain as the needle goes into the artery. Getting a blood sample from an artery is usually more painful than getting blood from a vein, a more common type of blood test procedure.

Once the syringe is filled with blood, your provider will put a bandage over the puncture site. After the procedure, you or a provider will need to apply firm pressure to the site for 5–10 minutes, or even longer if you are taking a blood-thinning medicine.

Will I need to do anything to prepare for the test?

If your blood sample is taken from your wrist, your health care provider may perform a circulation test called an Allen test before taking the sample. In an Allen test, your provider will apply pressure to the arteries in your wrist for several seconds.

If you are on oxygen therapy, your oxygen may be turned off for about 20 minutes before the test. This is called a room air test. This won’t be done if you are unable breathe without the oxygen.

Are there any risks to the test?

There is very little risk to having a blood oxygen level test. You may have some bleeding, bruising, or soreness at the spot where the needle was put in. Though problems are rare, you should avoid lifting heavy objects for 24 hours after the test.

What do the results mean?

If your blood oxygen level results are not normal, it may mean you:

  • Are not taking in enough oxygen
  • Are not getting rid of enough carbon dioxide
  • Have an imbalance in your acid-base levels

These conditions can be signs of a lung or kidney disease. The test can’t diagnose specific diseases, but if your results are not normal, your health care provider will order more tests to confirm or rule out a diagnosis. If you have questions about your results, talk to your health care provider.

Is there anything else I need to know about blood oxygen level tests?

Another type of test, called pulse oximetry, also checks blood oxygen levels. This test doesn’t use a needle or require a blood sample. In pulse oximetry, a small clip-like device with a special sensor is attached to your fingertip, toe, or earlobe. Since the device measures oxygen “peripherally”(in an outer area), the results are given as peripheral oxygen saturation, also known as SpO2.

Your blood oxygen level refers to the amount of oxygen you have circulating in your blood. It is most commonly measured through a process known as “pulse oximetry.” Low blood oxygen levels can be associated with a variety of different health issues.

Below we’ll take a deeper dive into the basics of blood oxygen levels and pulse oximetry.

What Does Blood Oxygen Level Show?

The human body needs to constantly be supplied with oxygen in order to function. We breathe it in through the nose and mouth, then our lungs transfer it into the bloodstream where it is then distributed throughout the body. Oxygen is carried in your blood by red blood cells. As it travels around the body, oxygen helps provide energy, replace worn out cells, and support internal organs and systems.

Your blood oxygen level shows how much oxygen is being circulated by your red blood cells, and it is very closely regulated by your body. Keeping it within a specific range is necessary to ensure that all the cells in your body are getting enough oxygen. Maintaining the proper balance of oxygen saturation in your blood is extremely important for your health.

Blood oxygen level indicates how efficiently your body is dispersing oxygen from your lungs to your cells. Low levels can be a sign that there is something wrong with your lungs or blood circulation.

If you’ve tested positive for COVID-19 and are experiencing symptoms, low blood oxygen levels may be a red flag that you’re in need of medical attention.

What is a Normal Blood Oxygen Level?

There are two ways to measure your blood oxygen level. One is an arterial blood gas test, which is uncomfortable and invasive and requires a doctor to draw blood from one of your arteries (arteries carry oxygenated blood and deliver it to the body, then veins return it to the heart).

The other is with pulse oximetry, which does it quickly and painlessly by shining light through capillary veins near the surface of your skin. Pulse oximetry measures the oxygen saturation of your blood as a percentage, known as SpO2.

A normal blood oxygen level is between 95% and 100%.

This number is likely to vary for people with lung diseases and other particular medical issues. An SpO2 below 90% is considered low, and referred to as hypoxemia.

Causes and Symptoms of Low Blood Oxygen Levels

Here are several potential symptoms of low blood oxygen levels:

  • Heavy breathing or shortness of breath
  • Chest pains
  • Elevated heart rate and blood pressure
  • Headaches and dizziness
  • Restless feeling
  • Confusion or loss of coordination
  • Impaired vision

Low levels of blood oxygen can be caused by changes in your environment, most notably high-altitude conditions where there is less oxygen in the air.

From a medical standpoint, a low SpO2 may be caused by anemia (insufficient red blood cells) or congenital heart diseases where the heart is unable to pump enough oxygenated blood. Additionally, lung ailments that decrease your body’s ability to take in oxygen often lead to low blood oxygen levels as well, including:

  • Asthma
  • Bronchitis
  • Pneumonia
  • COVID-19 or other viral infections
  • Emphysema (when the lungs’ air sacs are damaged, usually from smoking)
  • Pulmonary edema (fluid buildup that causes lungs to swell) or fibrosis (lung tissue becomes scarred)

How WHOOP Monitors Blood Oxygen

While the most familiar pulse oximeters are those that are placed on your finger, the same technology is utilized in many other devices, including the WHOOP 4.0, to monitor blood oxygen levels from the wrist.

The WHOOP 4.0 does this by sending two wavelengths of light (red and infrared) through your skin where it is absorbed and reflected by blood vessels. The red and infrared light each get absorbed differently by hemoglobin (the red blood cells that can bind with oxygen), and their absorption changes if the hemoglobin is oxygenated or not. By comparing the relative amount of light that gets reflected back from each of the wavelengths, we are able to track what percentage of red blood cells are oxygenated.

So, for example, if 96% of them are oxygenated and 4% are not, then your SpO2 is 96%.

The WHOOP 4.0 measures your blood oxygen level while you’re sleeping at night (which allows for the most consistent and reliable readings), then reports it to you each morning via the Health Monitor, which tracks key vitals including live heart rate, resting heart rate, heart rate variability, respiratory rate, and skin temperature.

The WHOOP 4.0 Health Monitor alerts you if blood oxygen levels or other key physiological metrics stray too far from their normal baseline.

The products and services of WHOOP are not medical devices, are not intended to diagnose COVID-19, the flu or any other disease, and should not be used as a substitute for professional medical advice, diagnosis or treatment. All content available through the products and services of WHOOP is for general informational purposes only.

How to measure blood oxygen

Blood oxygen measurement or Pulse Oximetry is the measurement of the saturated the blood is with oxygen. It is arguably the fifth vital signs to check for medically, because as you know, oxygen is quite important to humans and its absence is otherwise fatal. As a result of this, wearables like fitness trackers and smartwatches have incorporated the tech to measure this important health reading.

In that regard, the smartwatch is concerned with Sp02 which is peripheral oxygen saturation and it is very important as regards continuous oxygen level measurement in the blood. Coupled with the fact that it is non-invasive, SpO2 measurement is the popular method of blood oxygen saturation. Despite arterial oxygen saturation (SaO2) being a more accurate, blood sample has to be drawn and then tested so it can’t cater for continuous blood oxygen measurement. In other words, SpO2 is a more practical and convenient way for pulse oximetry which makes it the goto option.

The physical properties of oxygenated and deoxygenated blood form the basis for the measurement of blood oxygen level. In case you haven’t noticed, oxygenated blood is usually bright red while deoxygenated blood is dark red. This is because oxygenated blood reflects more red light while deoxygenated blood absorbs red light.

How does a smart watch measure blood oxygen?

Conventional medical pulse oximeter employs the transmissive pulse oximetry method where peripheral parts of the body like ear lobe, fingertips and toes in babies are used. The most popular involves passing light through the finger and measuring light (infrared and red light) that is absorded and able to pass through the finger to determine blood oxygen level.

How to measure blood oxygen

Smartwatch measures blood oxygen level using another type of SpO2 technique called reflectance pulse oximetry which simply put measure light reflected instead of light passing through the body. As opposed to the transmissive method, you can measure blood oxygen level from other parts of the body like the chest and wrist.

In this method, the light projected to the body surface usually infrared and red light is reflected off the subcutaneous tissue or bone to the sensor on the smartwatch where the difference between the light emitted and reflected used to determine blood oxygen level.

How to measure blood oxygen

This makes it the ideal way for smartwatches and fitness trackers alike to measure blood SpO2. It is especially advantageous during low temperature when blood flow to the tips of the body where transmittance pulse oximetry takes place is reduced.

Smartwatch that can measure blood oxygen (SpO2)

There are quite a number of smartwatch out there that can measure blood oxygen saturation from different brands like Fitbit, Garmin, Samsung, Apple and so on. Here are a few smartwatches you can cop that can measure your blood oxygen levels with.

  • Fitbit Versa 3
  • Garmin Forerunner 245
  • Fitbit Sense
  • Garmin Vivosmart 4
  • Garmin Fenix 6
  • Fitbit Ionic
  • Withings ScanWatch

Conclusion

While it is nice to be able to check blood oxygen level on your wrist at any time, the reflectance-based oximetry which smartwatch use is relatively underdeveloped in comparison to the transmissive method. Besides this, smartwatch blood oxygen level measurement is not on par with clinical standards.

In fact, there is no medical certification for the oximeter on smartwatches which shows it is not meant for diagnosis or wellness. Rather it is more for fitness purposes as it is often inaccurate in its results. That being said, to have the best chance of getting a good result, you will have to stay still when taking SpO2 measurements on your smartwatch.

How to measure blood oxygen

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Отключение фоновых измерений в режиме сна и театра

Во время измерения уровня кислорода в крови на Ваше запястье светит яркий красный луч, который может быть более заметным в темноте. Если этот свет Вас отвлекает, измерение можно отключить.

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Измерения уровня кислорода в крови

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Откройте приложение «Кислород в крови» на Apple Watch.

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Примечание. Для более точной работы необходимо, чтобы задняя поверхность Apple Watch соприкасалась с кожей. Чтобы успешно измерить уровень кислорода в крови, рекомендуется не затягивать ремешок Apple Watch слишком туго, однако он также не должен сидеть слишком свободно. Между ремешком и Вашей кожей должен оставаться небольшой зазор, позволяющий коже дышать. Подробную информацию см. в статье службы поддержки Apple о том, Как использовать приложение «Кислород в крови» на Apple Watch Series 6.

How to measure blood oxygen

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