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2. Blood Oxygen Levels Chart
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Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal arterial blood oxygen saturation levels in humans are 95–100 percent. If the level is below 90 percent, it is considered low and called hypoxemia.^[1] Arterial blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to respiratory or cardiac arrest. Oxygen therapy may be used to assist in raising blood oxygen levels. Oxygenation occurs when oxygen molecules (O
₂) enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood. Oxygenation is commonly used to refer to medical oxygen saturation.

Definition[edit]

Pulse oximetry is a method used to estimate the percentage of oxygen bound to hemoglobin in the blood. This approximation to SaO 2 is designated SpO 2 (peripheral oxygen saturation). Pulse oximetry measures the amount of oxygen being carried in your blood, as a percentage. The measurement is taken at the finger using a Pulse Oximeter. This measurement is known as the Sp02 – the saturation of peripheral oxygen – and it is an estimate of.

In medicine, oxygen saturation, commonly referred to as 'sats', measures the percentage of hemoglobin binding sites in the bloodstream occupied by oxygen.^[2] At low partial pressures of oxygen, most hemoglobin is deoxygenated. At around 90% (the value varies according to the clinical context) oxygen saturation increases according to an oxygen-hemoglobin dissociation curve and approaches 100% at partial oxygen pressures of >11 kPa. A pulse oximeter relies on the light absorption characteristics of saturated hemoglobin to give an indication of oxygen saturation.

Physiology[edit]

The body maintains a stable level of oxygen saturation for the most part by chemical processes of aerobic metabolism associated with breathing. Using the respiratory system, red blood cells, specifically the hemoglobin, gather oxygen in the lungs and distribute it to the rest of the body. The needs of the body's blood oxygen may fluctuate such as during exercise when more oxygen is required ^[3] or when living at higher altitudes. A blood cell is said to be 'saturated' when carrying a normal amount of oxygen.^[4] Both too high and too low levels can have adverse effects on the body.^[5]

Measurement[edit]

An SaO₂ (arterial oxygen saturation, as determined by an arterial blood gas test^[6]) value below 90% indicates hypoxemia (which can also be caused by anemia). Hypoxemia due to low SaO₂ is indicated by cyanosis. Oxygen saturation can be measured in different tissues:^[6]

• Venous oxygen saturation (SvO₂) is the percentage of oxygenated hemoglobin returning to the right side of the heart. It can be measured to see if oxygen delivery meets the tissues' demands. SvO₂ typically varies between 60% and 80%.^[7] A lower value indicates that the body is in lack of oxygen, and ischemic diseases occur. This measurement is often used under treatment with a heart lung machine (extracorporeal circulation), and can give the perfusionist an idea of how much flow the patient needs to stay healthy.
• Tissue oxygen saturation (StO₂) can be measured by near infrared spectroscopy. Although the measurements are still widely discussed, they give an idea of tissue oxygenation in various conditions.
• Peripheral oxygen saturation (SpO₂) is an estimation of the oxygen saturation level usually measured with a pulse oximeter device. It can be calculated with pulse oximetry according to the formula^[6] where HbO₂ is oxygenated hemoglobin (oxyhemoglobin) and Hb is deoxygenated hemoglobin.

Pulse oximetry[edit]

Pulse oximetry is a method used to estimate the percentage of oxygen bound to hemoglobin in the blood.^[8] This approximation to SaO₂ is designated SpO₂ (peripheral oxygen saturation). The pulse oximeter consists of a small device that clips to the body (typically a finger, an earlobe or an infant's foot) and transfers its readings to a reading meter by wire or wirelessly. The device uses light-emitting diodes of different colours in conjunction with a light-sensitive sensor to measure the absorption of red and infrared light in the extremity. The difference in absorption between oxygenated and deoxygenated hemoglobin makes the calculation possible.^[6]

Medical significance[edit]

Healthy individuals at sea level usually exhibit oxygen saturation values between 96% and 99%, and should be above 94%. At 1,600 meters' altitude (about one mile high) oxygen saturation should be above 92%.^[9]

An SaO₂ (arterial oxygen saturation) value below 90% causes hypoxia (which can also be caused by anemia). Hypoxia due to low SaO₂ is indicated by cyanosis, but oxygen saturation does not directly reflect tissue oxygenation. The affinity of hemoglobin to oxygen may impair or enhance oxygen release at the tissue level. Oxygen is more readily released to the tissues (i.e., hemoglobin has a lower affinity for oxygen) when pH is decreased, body temperature is increased, arterial partial pressure of carbon dioxide (PaCO₂) is increased, and 2,3-DPG levels (a byproduct of glucose metabolism also found in stored blood products) are increased. When the hemoglobin has greater affinity for oxygen, less is available to the tissues. Conditions such as increased pH, decreased temperature, decreased PaCO₂, and decreased 2,3-DPG will increase oxygen binding to the hemoglobin and limit its release to the tissue.^[10]

See also[edit]

References[edit]

1. ^'Hypoxemia (low blood oxygen)'. Mayo Clinic. mayoclinic.com. Retrieved 6 June 2013.
2. ^Kenneth D. McClatchey (2002). Clinical Laboratory Medicine. Philadelphia: Lippincott Williams & Wilkins. p. 370. ISBN9780683307511.
3. ^'Understanding Blood Oxygen Levels at Rest'. fitday.com. fitday.com. Retrieved 6 June 2013.
4. ^Ellison, Bronwyn. 'NORMAL RANGE OF BLOOD OXYGEN LEVEL'. Livestrong.com. Livestrong.com. Retrieved 6 June 2013.
5. ^'Hypoxia and Hypoxemia: Symptoms, Treatment, Causes'. WebMD. Retrieved 2019-03-11.
6. ^ ^abcd'Understanding Pulse Oximetry: SpO2 Concepts'. Philips Medical Systems. Retrieved 19 August 2016.
7. ^https://www.lhsc.on.ca/critical-care-trauma-centre/central-venous/mixed-venous-oxygen-saturation
8. ^Peláez EA, Villegas ER (2007). 'LED power reduction trade-offs for ambulatory pulse oximetry'. Conf Proc IEEE Eng Med Biol Soc. 2007: 2296–9. doi:10.1109/IEMBS.2007.4352784. ISBN978-1-4244-0787-3. PMID18002450. S2CID34626885.
9. ^'Normal oxygen level'. National Jewish Health. MedHelp. February 23, 2009. Retrieved 2014-01-28.
10. ^Schutz (2001). 'Oxygen Saturation Monitoring by Pulse Oximetry'(PDF). American Association of Critical Care Nurses. Archived from the original(PDF) on January 31, 2012. Retrieved September 10, 2011.

External links[edit]

Blood oxygen levels during sleep should be at a 95 percent saturation, which is considered normal, according to the American Sleep Apnea Association (AASM).

It is normal for blood oxygen levels to decrease during sleep. All body systems have altered basal function during your sleep, including breathing. You don’t breathe as deeply when you are sleeping, and not all your lung spaces function at full capacity. Because of this effect of sleep on breathing, it is normal for your sleep oxygen level to decrease below awake levels. Tests that show a waking oxygen level at or above 94 percent typically indicate a sleep oxygen level of at or above 88 percent.

However, when it persistently drops below maintenance levels, health problems can develop. In addition, certain medical conditions can lead to low oxygen while you are asleep.

Medical Disorders

Blood Oxygen Levels Chart

According to the Mayo Clinic, certain medical problems, especially of the cardiovascular and respiratory systems, can lead to blood oxygen below normal levels. The effects of these conditions can worsen while you are sleeping. The most common disorders include:

Diseases of the lungs:

Several lung diseases can narrow or block lung air spaces, inflame or scar lung tissue, and can also interfere with normal breathing patterns. These lung diseases include:

• Chronic obstructive pulmonary disease (COPD), such as emphysema and chronic bronchitis
• Asthma
• Cystic fibrosis, a genetic disease that causes a build of mucus in the lungs
• Pneumonia and other lung infections
• Smoking and lung cancer

Heart diseases:

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Disorders of the heart, which can interfere with blood flow, blood oxygen level, and oxygen supply to tissues include:

• Coronary heart disease, a build-up of plaques in the arteries of the heart
• Congestive heart failure with leakage of fluid into lung tissue
• Congenital heart disease, a developmental defect in the structure of the heart

Anemia:

The decrease in hemoglobin (Hgb) with anemia lowers the ability of your red blood cells to absorb oxygen from your lungs and carry it to your tissues. Abnormal Hgb, such as with sickle cell anemia, causes the same problem.

Obesity:

This a cause of sleep apnea where the throat becomes obstructed during sleep and interferes with breathing. Obesity also causes obesity hypoventilation syndrome (OHS), with diminished deep breathing and oxygen intake.

Drugs:

Chronic use of prescription or illegal opioids, sedatives, and recreational or other illegal drugs can depress the brain’s breathing center and therefore slow down your breathing and oxygen intake.

Alcohol:

Abuse of alcohol, especially at bedtime and mixed with drugs, can interfere with normal breathing and sufficient oxygen intake.

Health Consequences

A normal blood oxygen level is vital for normal tissue and cellular function. Therefore, low blood oxygen affects the function of every tissue in the body. A chronic problem of low oxygen levels while sleeping can increase the risk for several health consequences including:

• Sleep disorders, such as bouts of insomnia
• Poor sleep quality, such as restless sleep with several awakenings
• High blood pressure
• Cardiovascular disease including heart failure
• Cardiac arrhythmia and a risk for sudden death
• Type 2 diabetes
• Depressed brain function and possible brain damage
• Risk for loss of consciousness, coma, and death

If you think your oxygen level falls below normal while you are sleeping, consult with your doctor. He might suggest a sleep study as part of your evaluation. During an overnight stay in a sleep center, a technician monitors your breathing and other signs, as well as your blood O2 sat with a pulse oximeter during sleep.