Hypoxemia (Low Blood Oxygen)

Dr. Nabi Darya Vali (AIIMS)MBBS

June 12, 2020

June 12, 2020


Hypoxemia is a medical condition where there is critically low levels of arterial oxygen in the blood, and it can be life-threatening, as not enough oxygen supply to different organs of the body can lead to damage in the brain, liver or other organs within minutes of symptoms beginning to show up.

Hypoxemia is also a common problem people can face at high altitudes due to the low oxygen levels present in those areas, especially among people not used to breathing in such thin air.

Haemoglobin in our blood is responsible for carrying oxygen to the cells that are present throughout the human body, and the occurrence of such a situation can cause a person headaches followed by difficulty breathing, among other visible signs of discomfort. One gram of haemoglobin can transport about 1.37 ml of oxygen.

Sometimes, hypoxemia is also used interchangeably with hypoxia, although the two conditions are slightly different from each other. While hypoxemia refers to the low levels of oxygen in a person's blood, hypoxia means low levels of oxygen in the tissues. The presence of hypoxemia can lead to hypoxia.

The occurrence of hypoxemia in a person is a sign of poor blood circulation or a respiratory problem, and can be checked by measuring the oxygen levels from a blood sample taken from the arteries. A simple device such as a pulse oximeter, which just needs to be clipped on to a person's fingertip, can also be used to monitor a person's oxygen saturation levels in the blood. An arterial blood gas test can also be performed to get an accurate picture of the amount of oxygen in the blood.

Hypoxemia (low blood oxygen) symptoms

Symptoms of hypoxemia can range from mild to severe depending on a number of signs the person is experiencing. Signs of hypoxemia or low blood oxygen include:

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Hypoxemia (low blood oxygen) causes

Identifying hypoxemia, according to Lori A. Aronson's Complications in Anesthesia, is vital to the practice of anaesthesia, and to this effect, the use of a simple device such as the pulse oximeter has become a vital tool to monitor a patient's oxygen levels when administering anesthesia. One of the critical signs of hypoxemia, according to the author, is a decrease in the oxygen saturation levels in the blood.

Some of the possible causes of hypoxemia include underlying conditions such as:

  • Asthma: The narrowing of air passages in the lungs, asthma is a common breathing disorder among many people that experience hypoxemia.
  • COPD: A collective term for severe inflammatory lung diseases that cause obstruction to the flow of oxygen in the lungs, and as many as 65 million people are estimated to be suffering from mild to severe COPD around the world, according to the World Health Organization (WHO).
  • Emphysema: Emphysema is a type of COPD that causes damage to the lung tissue or the air sacs in the lungs, and causes breathing difficulties.
  • Bronchitis: The lining of the bronchial tubes is inflamed when a person has bronchitis, which carries air in and out of the lungs.
  • Acute respiratory distress syndrome (ARDS): A severe lung condition such as ARDS occurs when fluid gets filled up in the air sacs inside the lungs, which leads to the low amount of oxygen or higher amounts of carbon dioxide in the blood.
  • Pneumonia: An acute infection in the lungs in which there is an accumulation of fluid or pus in the air sacs, pneumonia can occur due to a variety of reasons.
  • Altitude sickness: The low air pressure at high altitudes can lead to hypoxemia and cause difficulty breathing followed by other symptoms of the condition like altitude sickness, and pulmonary edema if it worsens.
  • Heart diseases: Several heart diseases, defects and conditions are also known to cause hypoxemia in patients.
  • Anaemia: Anaemia is a condition where haemoglobin or the red blood cells (RBC) are reduced drastically.

Prevention of hypoxemia (low blood oxygen)

There are several reasons why oxygen in the blood can reduce, and this phenomenon is not only limited to chronic illness or development of a disease in the body. Some preventive measures can be taken to avoid the onset of hypoxemia among people:

  • Avoid smoking: Smoking is one of the primary causes of several respiratory illnesses and reduced capacity of the lungs to breathe in oxygen.
  • Protect yourself from smoke: Places that see constant fires, pollution or smoke coming out of factories are places one should avoid to keep their lungs safe from respiratory problems.
  • Regular exercise: While some respiratory illnesses may stop a person from pursuing intense physical activity, light exercise and movement are good to keep the lungs in good health and stop them from deteriorating further.
  • Deep breathing exercises: Deep breathing exercises such as a variety of techniques in yoga as well as other forms of focused, conscious breathing techniques can help keep the lungs working efficiently.
  • Stay hydrated: Keeping the body hydrated is one of the essential ways to maintain adequate levels of oxygen in the blood.
  • Eat healthily: A well-balanced diet rich in diverse nutrients can help in keeping the flow of oxygen in the blood at adequate levels. (Read more: Balanced diet)

Diagnosis of hypoxemia (low blood oxygen)

The presence of any of the symptoms mentioned above should be enough for you to visit a doctor and get it checked. The doctor will start by performing a physical exam and check your heart and lungs, besides looking for any visible signs such as a change in the colour of your fingernails, toes or lips.

Simple pulse oximetry—which can even be used at home—will then be performed to measure your oxygen saturation levels. A reading of over 95 is ideal for a healthy adult, but anything below 90 should be a cause for worry.

Breathing tests that require the patient to breathe into a tube, and how efficiently a patient is able to do it, is also one of the physical tests a doctor would perform. A blood sample could also be taken from one of the arteries that can further indicate blood oxygen levels with some more certainty, through an arterial blood gas test.

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Hypoxemia (low blood oxygen) treatment

Because hypoxemia can be caused due to an underlying illness, a proper diagnosis is required to get to the bottom of why the patient has low blood oxygen.

The lack of oxygen in the blood immediately calls for the need to boost oxygen levels in the body, and it can be done by providing the patient with supplemental oxygen. It is especially necessary if there is a danger of the situation worsening to hypoxia, which can affect the functioning of important organs of the body such as the brain or the liver.

Patients in critical care could be under intubation or mechanical ventilator support, while those suffering from hypoxemia at high altitudes are usually required to get down to lower altitudes, as the situation could worsen with the administration of supplemental oxygen. (Read more: What is oxygen therapy?)

Certain medications used in the treatment and management of asthma or other respiratory illnesses are also beneficial to treat the immediate onset of hypoxemia among patients.


  1. Sarkar M et al. Mechanisms of hypoxemia. Lung India. 2017 Jan-Feb; 34(1): 47–60. PMID: 28144061.
  2. Kent BD et al. Hypoxemia in patients with COPD: cause, effects, and disease progression. International Journal of Chronic Obstructive Pulmonary Disease. 2011; 6: 199–208. PMID: 21660297.
  3. Loeppky JA et al. Hypoxemia and Acute Mountain Sickness: Which Comes First? High Altitude Medicine & Biology. 2008;9(4): 271-9. PMID: 19115910.
  4. Aronson LA. Chapter 157 - Hypoxemia. Complications in Anesthesia (Second Edition). 2007; Pages: 637-640.
  5. Hypoxemia vs. Hypoxia. New England Journal of Medicine. 1966 Apr; 274: 908-909.

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