What is oxygen level in human body

Blood oxygen levels (arterial oxygen) indicate oxygen levels present in the blood that flows through the arteries. 

• Blood oxygen levels can be checked by withdrawing blood from an artery in the wrist, elbow, or groin.
• You may feel a sharp pain when the needle enters the artery.
• The blood is put in an ABG machine (blood gas analyzer) that provides blood oxygen level readings in the form of the partial pressure of oxygen (PaO2).
• In clinical studies, the blood oxygen level measurement feature on the Apple Watch has shown good accuracy when compared to a traditional pulse oximeter, which is a device commonly used to measure blood oxygen levels.

What are normal oxygen levels by age?

• 95%-100%: Normal oxygen levels in a pulse oximeter usually range from 95%-100%. Note: Normal levels may vary if you have lung disorders. Your doctor can tell what levels are normal for you.
• Below 95%: People with SpO2 level fall below 95% such as 92% should see a healthcare provider as it may be a sign of hypoxemia.
• Below 80-85%: The brain gets affected when the SpO2 level falls below 80-85%.
• Below 67%: Cyanosis develops when the SpO2 level drops below 67%.

Pulse oximetry may be slightly less accurate than ABG but is easier to perform than ABG tests when results are needed quickly. 
 

Asthma and Low Blood Oxygen Level

What are asthma symptoms and signs?

Many of the symptoms and signs of asthma are nonspecific and can be seen in other conditions as well. Symptoms that might suggest conditions other than asthma include new symptom onset in older age, the presence of associated symptoms (such as chest discomfort, lightheadedness, palpitations, and fatigue), and lack of response to appropriate medications for asthma.

The physical exam in asthma is often completely normal. Occasionally, wheezing is present. In an asthma exacerbation, the respiratory rate increases, the heart rate increases, and the work of respiration increases. Individuals often require accessory muscles to breathe, and breath sounds can be diminished. It is important to note that the blood oxygen level typically remains fairly normal even in the midst of a significant asthma exacerbation. Low blood oxygen level is therefore concerning for impending respiratory failure.

Read more about asthma symptoms, causes, treatment, and diagnosis. »

How are blood oxygen levels checked using the ABG test?

• Above 120 mmHg: Hyperoxemia is defined as blood oxygen levels above 120 mmHg. Hyperoxemia is mostly seen in hospitals when patients are exposed to high pressures of supplemental oxygen for prolonged periods (3 to more than 10 hours).
• 75-100 mmHg: Normal arterial oxygen pressure (PaO2) is approximately 75 to 100 millimeters of mercury (75-100 mmHg).
• Below 75 mmHg: When the levels drop below 75 mmHg, the condition is called hypoxemia.
• Below 60 mmHg: Levels below 60 mmHg are considered very low and indicate the need for supplemental oxygen. Supplemental oxygen is provided through an oxygen cylinder that is connected to the nose via a tube, with or without a mask.

SLIDESHOW

What causes blood oxygen levels to become low?

Blood oxygen levels can get low due to any of the problems that include:

• Low air oxygen levels: Atmospheric oxygen becomes extremely low at high altitudes such as mountainous regions.
• Decreased capacity of the body to take in oxygen:
  • This can be caused by lung conditions that include:
    • Asthma
    • Emphysema (damage of the air sacs in the lung)
    • Bronchitis
    • Pneumonia
    • Pneumothorax (leaking of air in the space between the lung and chest wall)
    • Acute respiratory distress syndrome (ARDS)
    • Pulmonary edema (the lung swells due to build-up of fluid)
    • Pulmonary fibrosis (scarring of the lungs)
    • Interstitial lung disease (a large group of lung disorders that generally cause progressive scarring of the lungs)
    • Viral infections such as COVID-19
• Other conditions include:
  • Anemia
  • Sleep apnea (temporary cessation of breathing during sleep)
  • Smoking
• Decreased capacity of the heart to supply the oxygenated blood back to the lungs: The most common causes are congenital heart diseases (heart defects present by birth).

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What are the signs and symptoms of low blood oxygen levels (hypoxemia)?

Hypoxemia can give rise to many signs and symptoms depending on its severity, which may include:

• Headache (mild to severe)
• Shortness of breath
• Dizziness
• Coughing
• Wheezing (breathing with a whistling or rattling sound in the chest)
• Confusion
• Rapid heartbeat
• Cyanosis (bluish color in the skin, fingernails, and lips)

Not having enough blood oxygen levels results in inadequate oxygen supply to the organs and tissues of the body. Severe hypoxemia can become dangerous. If left untreated for a long time, it can end up affecting the brain or heart.

How is hypoxemia treated?

Treating hypoxemia involves measures that increase the levels of oxygen in the blood, which is achieved by:

• Treating underlying conditions: Treating the cause of hypoxemia is the most important part of the therapy that gives long-lasting effects. Many times, medications are given through an inhaler that quickly enables you to breathe the medicine into your lungs.
• Oxygen therapy: You are given supplemental oxygen through an oxygen cylinder (which can be portable). The pressure of delivered oxygen can be controlled.

How can you prevent hypoxemia?

You can maintain your normal blood oxygen levels after you recover from hypoxemia. Lifestyle changes that can help prevent hypoxemia include:

• Deep breathing exercises
• Mild exercise such as walking or as advised by your doctor
• Yoga
• Eat a healthy, well-balanced diet
• Drink water adequately
• Quit smoking

QUESTION

Medically Reviewed on 12/21/2022

References

Hypoxemia. Available at: https://www.mayoclinic.org/symptoms/hypoxemia/basics/definition/sym-20050930

Hafen BB, et al. Oxygen Saturation. In: StatPearls [Internet]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK525974/

Cooper JS, et al. Oxygen Toxicity. In: StatPearls [Internet]. Available from: https://www.ncbi.nlm.nih.gov/books/NBK430743/

Starr N, et al. Pulse oximetry in low-resource settings during the COVID-19 pandemic. The Lancet Global Health. 2020 Sep 1;8(9):e1121-2.

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  REFERENCES:
  
  Harman, EM, MD. "Acute Respiratory Distress Syndrome Clinical Presentation." Medscape. Updated: Aug 11, 2016.
  
  Harman, EM, MD. "Acute Respiratory Distress Syndrome." Medscape. Updated: Aug 11, 2016.
  
  PubMed Health. "ARDS." Updated: Jun 11, 2014.
  
  Reynolds, HN. et al. Acute respiratory distress syndrome: estimated incidence and mortality rate in a 5 million-person population base. Crit Care. 1998; 2(1): 29–34. Published online 1998 Mar 12. doi: 10.1186/cc121

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  What is normal oxygen level by age?

  Oxygen saturation levels (SpO2) between 95 to 100 percent are considered normal for both adults and children (below 95% is considered abnormal). People over 70 years of age may have oxygen levels closer to 95%. Normal oxygen saturation levels (SpO2) are between 95 to 100 percent for both adults and children.

  What is a dangerously low oxygen level?

  People should contact a health care provider if their oxygen saturation readings drop below 92%, as it may be a sign of hypoxia, a condition in which not enough oxygen reaches the body's tissues. If blood oxygen saturation levels fall to 88% or lower, seek immediate medical attention, says Dr.

  Is 92 a good oxygen level?

  A normal oxygen saturation level ranges between 95 percent and 100 percent. Saturation levels may be somewhat lower and considered acceptable if you have a lung disease such as COPD or pneumonia. Levels may also be lower if you live in an area with higher elevation.

  How can I raise my oxygen level quickly?

  How to Increase Your Blood Oxygen Level.

  Stand or sit up straight. Rather than lying down, which may put pressure on your lungs and make it harder to breathe..

  Cough. If you have a cold or the flu, difficulty breathing can decrease oxygen saturation in your blood. ... .

  Go outside. ... .

  Drink lots of water. ... .

  Take slow, deep breaths..