The cells of the human body require a constant supply of oxygen to produce the energy necessary to accomplish their life-sustaining functions. Oxygen derived from the air is delivered via the bloodstream to the body organs and tissues. A low blood oxygen level, or hypoxemia, can occur due to reduced environmental oxygen or a problem affecting the respiratory or circulatory system. In many people with hypoxemia, several factors contribute to the low blood oxygen level.
Reduced Environmental Oxygen and Hypoventilation
Breathing in a sufficient amount of oxygen from the air is the first step in ensuring adequate oxygen delivery to the body tissues. A reduced amount of oxygen in the air can result in hypoxemia. This most commonly occurs in people who rapidly ascend to extremely high altitudes, such as mountain climbers. Breathing too slowly or too shallowly -- or hypoventilation -- can also lead to hypoxemia. Hypoventilation leads to inadequate oxygen intake by the lungs and a buildup of carbon dioxide in the blood, both of which contribute to hypoxemia.
- Breathing in a sufficient amount of oxygen from the air is the first step in ensuring adequate oxygen delivery to the body tissues.
- Hypoventilation leads to inadequate oxygen intake by the lungs and a buildup of carbon dioxide in the blood, both of which contribute to hypoxemia.
Signs of Poor Oxygen Supply
Oxygen crosses into the bloodstream via tiny air sacs in the lungs called alveoli. A variety of lung diseases can interfere with the uptake of oxygen by the bloodstream leading to hypoxemia. With pneumonia, infection leads to fluid accumulation in the air sacs that impairs oxygen transfer into the bloodstream. Chronic obstructive pulmonary disease (COPD) damages the small airways and alveoli, impairing gas exchange and often leading to low blood oxygen levels 3. Other lung diseases that lead to persistent inflammation or scarring of the airways, or alveolar damage can also lead to hypoxemia. Examples include cystic fibrosis, poorly controlled asthma, idiopathic pulmonary fibrosis and sarcoidosis.
- Oxygen crosses into the bloodstream via tiny air sacs in the lungs called alveoli.
- A variety of lung diseases can interfere with the uptake of oxygen by the bloodstream leading to hypoxemia.
The respiratory and circulatory systems work together to ensure that adequate oxygen is transferred from the lungs to the bloodstream and subsequently delivered to the body. Therefore, problems with the circulatory system that interfere with normal blood flow through the lungs can lead to hypoxemia. Heart failure, for example, often triggers abnormally high pressure in the lung circulation. This can provoke fluid buildup in the air sacs and lead to hypoxemia. An abrupt drop in blood oxygen level can occur when a blood clot lodges in the pulmonary circulation. This condition, known as a pulmonary embolism or PE, obstructs blood flow through the lungs, interfering with oxygen uptake. Malformations of the heart or lung blood vessels that lead to blood bypassing the lungs can also lead to varying degrees of hypoxemia.
- The respiratory and circulatory systems work together to ensure that adequate oxygen is transferred from the lungs to the bloodstream and subsequently delivered to the body.
- An abrupt drop in blood oxygen level can occur when a blood clot lodges in the pulmonary circulation.
The Effects of pCO2 on Respiration
Red blood cells transport oxygen from the lungs to the body organs and tissues via a carrier molecule called hemoglobin. A deficiency of red blood cells, or anemia, limits the oxygen-carrying capacity of the blood, potentially leading to reduced total oxygen content in the bloodstream.
Warnings and Precautions
Hypoxemia ranges from mild to severe, but even a mild decrease in blood oxygen requires medical evaluation to determine the underlying cause and best treatment. Signs and symptoms develop when a low blood oxygen level leads to an oxygen deficiency in the body tissues, which is known as hypoxia. Signs and symptoms of hypoxia are more likely to occur when the condition is severe and develops rapidly. Seek emergency medical care if you experience difficulty breathing or chest pain. Other warning signs and symptoms of hypoxia include: -- shortness of breath or breathlessness with minimal exertion -- increased heart and breathing rate -- lightheadedness or dizziness -- frequent headaches -- irritability, restlessness or confusion
Reviewed and revised by: Tina M. St. John, M.D.
- Hypoxemia ranges from mild to severe, but even a mild decrease in blood oxygen requires medical evaluation to determine the underlying cause and best treatment.
- Signs and symptoms develop when a low blood oxygen level leads to an oxygen deficiency in the body tissues, which is known as hypoxia.
Signs of Poor Oxygen Supply
The Effects of pCO2 on Respiration
What Are the Steps of Breathing?
The Difference Between Asthma and Pneumonia
The Effects of Mouth Breathing While on Oxygen
The Effects of Alcohol on Oxygen Absorption
Vitamin Deficiencies and Causes of Fainting
Dangerous Blood Oxygen Levels
What Are the Causes of Infiltration of Lungs?
Long-Term Effects of Exercise on the Respiratory System
- Molecular and Cellular Respiration: High Altitude Hypoxia: An Intricate Interplay of Oxygen Responsive Macroevents and Micromolecules
- Clinics in Chest Medicine: Pathophysiology of Pneumonia
- International Journal of Chronic Obstructive Pulmonary Disease: Hypoxemia in Patients With COPD: Cause, Effects, and Disease Progression
- Merck Manual Professional Version: Pulmonary Edema
- Concepts in Medical Physiology; Julian Seifter, et al.
- Atlas of Clinical Hematology; James O. Armitage
- Kent BD, Mitchell PD, Mcnicholas WT. Hypoxemia in patients with COPD: cause, effects, and disease progression. Int J Chron Obstruct Pulmon Dis. 2011;6:199-208. doi:10.2147/COPD.S10611
- Cleveland Clinic. Hypoxemia. Updated March 7, 2018.
- Dodd J, Getov S, Jones P. Cognitive function in COPD. European Respiratory Journal. 2010;35(4):913-922. doi:10.1183/09031936.00125109
- Ebner, F., Ullén, S., Åneman, A. et al. Associations between partial pressure of oxygen and neurological outcome in out-of-hospital cardiac arrest patients: an explorative analysis of a randomized trial. Crit Care 2019;23(1):30. doi:10.1186/s13054-019-2322-z
- Duke T, Peel D, Graham S, Howie S, Enarson PM, Jacobson R. Oxygen concentrators: a practical guide for clinicians and technicians in developing countries. Ann Trop Paediatr. 2010;30(2):87-101.
- Tiep B, Carter R, Zachariah F, et al. Oxygen for end-of-life lung cancer care: managing dyspnea and hypoxemia. Expert Rev Respir Med. 2013;7(5):479-90.
- Sarkar M, Niranjan N, Banyal PK. Mechanisms of hypoxemia. Lung India. 2017;34(1):47-60. doi:10.4103/0970-2113.197116
- Majumdar SR, Eurich DT, Gamble JM, Senthilselvan A, Marrie TJ. Oxygen saturations less than 92% are associated with major adverse events in outpatients with pneumonia: a population-based cohort study. Clin Infect Dis. 2011;52(3):325-31. doi:10.1093/cid/ciq076
- Dorsch JJ, Wickwire EM. OSA/COPD overlap: convergence on a theme? J Clin Sleep Med. 2019;15(1):9-10. doi:10.5664/jcsm.7556
- Cleveland Clinic. Hypoxemia: prevention. Updated March 7, 2018.
Dr. Margaret Baker studied biochemistry, pharmacology and nutrition, and conducted research on cancer therapeutics. She served as a patent agent for the biopharmaceutical division of a Fortune 500 company. Dr. Baker has published in peer reviewed journals, e-Books, and is a frequent commenter on discoveries in the life sciences.