Hypoxia (Hypoxemia): Low Blood Oxygen Signs, Causes, Treatment (2024)

• Introduction
  • What is hypoxia and hypoxemia (low blood oxygen)?
• Types
  • What are the types of hypoxia and hypoxemia?
• Causes
  • What causes hypoxia and hypoxemia?
• Symptoms
  • What are the symptoms of hypoxia and hypoxemia?
• Diagnosis
  • How are hypoxia and hypoxemia diagnosed?
• Treatment
  • What is the treatment for hypoxia and hypoxemia?
• Life Expectancy
  • What’s the life expectancy of someone with hypoxemia?
• Complications
  • What are complications of hypoxia?
• Prevention
  • Can hypoxia and hypoxemia be prevented?
• Respiratory Failure
  • What is respiratory failure with hypoxia?

What is hypoxia and hypoxemia (low blood oxygen)?

Hypoxia is a state of insufficient oxygen supply for normal life functions, and hypoxemia is a state of low arterial oxygen supply.

Hypoxia vs hypoxemia: What’s the difference?

Hypoxia is a condition or state in which the supply of oxygen in the arteries is insufficient for normal life functions. Hypoxemia is a condition or state in which there is a low arterial oxygen supply. Hypoxia is sometimes used to describe both states (hypoxia and hypoxemia).

Within the body, hypoxemia can lead to hypoxia (tissue hypoxia) in various tissues and organs with the most severe being cerebral hypoxia which can rapidly result in brain damage or death.

Conversely, if a person experiences environmental hypoxia (low or absent oxygen in the environment from high altitudes or drowning, for example), the person can develop hypoxemia.

What are the types of hypoxia and hypoxemia?

• Hypoxic hypoxia (arterial hypoxia or generalized hypoxia):
  • Low oxygen levels or lack of oxygen, leading to insufficient air available to the lungs. It can occur due to high altitude, closed breathing space, etc.
  • Asthma and other disorders of the lungs, heart, or brain can also cause hypoxic ischemia (inadequate blood supply).
• Anemic hypoxia:
  • Decreased hemoglobin levels in the blood, hence there is decreased oxygen capacity of the blood. Hemoglobin is a protein in red blood cells (RBC) that binds to oxygen and supplies oxygen to the entire body. It also gives blood its characteristic red color.
  • Anemic hypoxia can be caused by heavy blood loss, decreased RBCs, or decreased hemoglobin levels due to severe iron deficiency or hemoglobin deformity.
• Ischemic/Stagnant hypoxia:
  • Inadequate blood flow to the body tissues because the velocity of blood flow decreases.
  • This could be due to heart failure, severe blood loss, or clots in a blood vessel.
• Dysoxic/Histotoxic/Tissue hypoxia:
  • The oxygen delivered to the tissues is normal, but the cells are unable to use the oxygen, for example, cyanide poisoning.
  • Cyanide binds to the oxygen-binding proteins and other parts of the cells in the tissue, preventing the interaction and consumption of oxygen in the tissues.

What causes hypoxia and hypoxemia?

The causes of both environmental and tissue hypoxia often result in the intermediate state of hypoxemia; thus, the causes of any type of hypoxia are also potential causes of hypoxemia.

Some of the many causes of the condition include:

• Chemical or gas poisoning (for example cyanide, carbon monoxide)
• The low or absent concentration of oxygen (for example, high altitudes reached without supplemental oxygen as seen in mountain climbing, aviation, drowning, or fires)
• Lung problems, for example:
  • Chronic obstructive pulmonary disease (COPD)
  • Emphysema
  • Chronic bronchitis
  • Bronchitis
  • Pulmonary edema
  • Lung cancer
  • Pneumonia
  • Sleep apnea (nocturnal hypoxemia)
  • Pneumothorax
  • Asthma
  • COVID-19
• Any medications that reduce or stop the effort for breathing (for example, fentanyl and other narcotics, or general anesthetic medications)
• Heart problems (for example, severe bradycardia, and ventricular fibrillation)
• Anemia and/or conditions that destroy red blood cells
• Reducing or stopping arterial blood flow to any tissue for an organ (for example, arterial blockage by a clot or by injury such as a gunshot)

What causes anemic hypoxia?

Anemic hypoxia occurs when the blood’s ability to carry oxygen decreases, which leads to insufficient oxygen reaching body tissues. The causes of anemic hypoxia can include:

• Iron deficiency anemia: A condition where there's a lack of iron in the body, leading to a decreased production of hemoglobin and red blood cells.
• Vitamin B12 deficiency anemia: Deficiency in vitamin B12 can lead to the production of abnormally large red blood cells, which are not as efficient at carrying oxygen.
• Folate deficiency anemia: Lack of folate can result in the production of larger, ineffective red blood cells.
• Chronic diseases: Certain chronic diseases, such as chronic kidney disease, cancer or inflammatory diseases, can interfere with the body's ability to produce red blood cells or hemoglobin.
• Genetic disorders: Some inherited conditions, such as thalassemia or sickle cell anemia, affect the structure or production of hemoglobin, leading to anemia and reduced oxygen-carrying capacity.
• Blood loss: Acute or chronic blood loss, whether through injury, menstruation, gastrointestinal bleeding or other causes, can lead to anemia and decreased oxygen supply to tissues.
• Bone marrow disorders: Conditions affecting the bone marrow, where blood cells are produced, can result in decreased red blood cell production and anemia.
• Medications/treatments: Certain medications or treatments, such as chemotherapy or radiation therapy, can suppress bone marrow function and lead to anemia.
• Dietary factors: Poor nutrition or dietary deficiencies in nutrients necessary for red blood cell production, such as iron, vitamin B12 or folate, can contribute to anemia.

It’s important to address these underlying causes to improve oxygen supply to the tissues. If you suspect anemic hypoxia, seek medical attention promptly.

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What are the symptoms of hypoxia and hypoxemia?

Hypoxia symptoms and/or hypoxemia symptoms may be acute or chronic.

Acute hypoxia symptoms can come on rapidly and usually consist of:

• Shortness of breath
• Rapid breathing
• A fast heart rate

Other associated symptoms that can occur in both acute and chronic forms of the conditions include:

• Wheezing
• Sweating
• Coughing

What is the first sign of hypoxia?

Restlessness is an early sign of hypoxia. When the body's oxygen levels are low, it can cause agitation, discomfort, and restlessness to compensate for the lack of oxygen. Restlessness is frequently accompanied by other hypoxia symptoms such as shortness of breath (dyspnea), rapid heart rate (tachycardia), bluish discoloration (cyanosis), confusion, and anxiety. It is critical to recognize and treat these early warning signs to avoid complications.

Common signs and symptoms of hypoxia

Hypoxia refers to low oxygen levels in tissues throughout the body, which leads to the following signs and symptoms:

• Shortness of breath (dyspnea): Similar to hypoxemia, difficulty breathing is a hallmark symptom of hypoxia as well.
• Confusion or cognitive impairment: As with hypoxemia, the brain is particularly sensitive to low oxygen levels, leading to confusion, memory problems and coordination issues.
• Restlessness: Hypoxia can cause a feeling of restlessness or agitation as the body tries to compensate for the lack of oxygen.
• Headache: Hypoxia can cause headaches, which may range from mild to severe and can be accompanied by other symptoms such as dizziness or nausea.
• Fatigue: Feeling unusually tired (fatigued) even after minimal exertion is common in hypoxia.
• Increased heart rate (tachycardia) and rapid breathing (tachypnea): These symptoms may also occur with hypoxia as the body attempts to compensate for the lack of oxygen.
• Blue tint to the skin (cyanosis): Like hypoxemia, hypoxia can cause a bluish tint to the skin, lips, and nail beds due to insufficient oxygen in the blood.
• Muscle weakness: Hypoxia can lead to weakness, especially during physical activity.
• Nausea and vomiting: Some individuals may experience nausea or vomiting as a result of hypoxia, particularly if the lack of oxygen is severe or prolonged.

Severe hypoxia can cause additional symptoms, including loss of consciousness, seizures, and even death if not treated promptly.

What happens to a person with hypoxia?

The affected individual may be mildly confused initially and appear weak or experience rapid skin color changes ranging from blue to cherry red (depending on the causes).

Severe symptoms seen with cerebral hypoxia include:

• Confusion
• Inability to communicate
• Coma, which can lead to death

The symptoms of cerebral hypoxia in pediatric patients can be similar to the above and may include:

• Lethargy
• Irritableness
• Anxiousness
• Inattentiveness
• Sitting up and leaning forward to improve diaphragmatic breathing
• Children with epiglottitis and airway restriction may drool and mainly breathe by mouth

Common signs and symptoms of hypoxemia

Hypoxemia specifically refers to low oxygen levels in the blood, which can lead to the following symptoms:

• Shortness of breath (dyspnea): This is often the most prominent symptom of hypoxemia. It's a sensation of not being able to get enough air, which can be mild to severe, depending on the level of oxygen deprivation.
• Rapid breathing (tachypnea): The body tries to compensate for low oxygen levels by increasing the rate of breathing, attempting to bring in more oxygen-rich air.
• Increased heart rate (tachycardia): Similar to rapid breathing, the heart rate increases to pump oxygen-deprived blood faster around the body.
• Cough: The body may try to clear the airways of any obstructions, leading to a persistent cough.
• Confusion or altered mental states: Oxygen is crucial for brain function, so low oxygen levels can lead to confusion, disorientation, difficulty concentrating and even loss of consciousness in severe cases.
• Blue tint to the skin (cyanosis): This occurs when oxygen levels in the blood are significantly reduced, causing the skin, lips and nail beds to take on a bluish tint due to poorly oxygenated blood.
• Dizziness or lightheadedness: Lack of oxygen to the brain can cause feelings of dizziness, lightheadedness or even fainting.
• Chest pain: In some cases, hypoxemia can lead to chest pain, which may be a sign of underlying heart or lung conditions exacerbated by low oxygen levels.

How are hypoxia and hypoxemia diagnosed?

In general, an individual patient’s hypoxemia is usually diagnosed by oxygen monitors placed on fingers or ears (pulse oximeter) and/or by determining the oxygen level in a blood gas sample (a sample of blood taken from an artery). Normal readings are about 95% to 100% oxygen saturation levels; generally, oxygen is supplied if the level is about 92% or below.

Other tests may be ordered to determine if other potential problems such as carbon monoxide poisoning are responsible for the hypoxia.

Pulmonary function tests may also be ordered along with other studies to help determine the cause of unexplained low oxygen saturation.

Hypoxia range

Hypoxia ranges typically refer to the levels of oxygen in the blood, which are measured using parameters such as partial pressure of oxygen (PaO2) or oxygen saturation (SpO2). Based on the severity of oxygen deprivation in the blood, hypoxia can be classified into these ranges: mild, moderate and severe.

Mild hypoxia (PaO2 60-80 mmHg/SpO2 90 to 94 percent): In mild hypoxia, the oxygen levels in the blood are slightly lower than normal but still within a relatively safe range for most individuals. Symptoms of mild hypoxia may include:

• Shortness of breath
• Rapid breathing
• Increased heart rate
• Fatigue
• Mild confusion

Mild hypoxia can occur during activities such as strenuous exercise at high altitudes or due to mild respiratory conditions.

Moderate hypoxia (PaO2 40 to 60 mmHg/SpO2 80 to 89 percent): Moderate hypoxia is characterized by a more significant decrease in oxygen levels in the blood, which can lead to more pronounced symptoms, which include:

• Severe shortness of breath
• Rapid breathing
• Increased heart rate
• Confusion and impaired coordination
• Headache

Moderate hypoxia can occur at high altitudes, during severe respiratory conditions or in situations where oxygen supply to the body is restricted.

Severe hypoxia (PaO2 less than 40 mmHg / SpO2 less than 80 percent): Severe hypoxia is a critical condition where oxygen levels in the blood are dangerously low, leading to potentially life-threatening consequences. Symptoms of severe hypoxia include:

• Extreme shortness of breath
• Rapid and shallow breathing
• Weak pulse
• Confusion
• Loss of consciousness
• Coma
• Death (if not treated promptly)

Severe hypoxia can result from conditions such as acute respiratory distress syndrome, severe lung infections, heart failure or carbon monoxide poisoning.

What is the treatment for hypoxia and hypoxemia?

How do you reverse hypoxia?

Hypoxia treatment (and/or hypoxemia treatment) involves giving additional oxygen to the patient and getting oxygen into the body (blood) as quickly as possible, especially if cerebral hypoxia is suspected, or to treat the underlying cause of the hypoxia.

Many patients will respond to additional oxygen supplied by a nasal cannula. The quicker the oxygen level reaches normal, the better the prognosis is for the patient. However, timing is very important, because cerebral hypoxia can occur within a few minutes and, in many patients, may not be reversible.

Some patients may be treated in a hyperbaric chamber that increases oxygen concentrations in the blood (used in carbon monoxide poisoning), while others may require mechanical ventilation (intubation) with oxygen supplied at higher-than-normal atmospheric concentrations.

Others, such as mountain climbers or airline passengers, may need only additional oxygen provided by oxygen masks until they reach lower levels where oxygen concentrations are closer to the normal levels (about 21%) in the atmosphere.

Care must be used when giving oxygen, as it can be toxic to tissues if it is used excessively (hyperoxia). Hyperoxia may cause:

• Vertigo (spinning sensation)
• Behavior changes
• Other central nervous system changes such as seizures and/or tissue damage, and may result in:
  • Pneumonia
  • Eye changes such as cataracts
  • Other organ diseases/injury

Hyperoxia may occur in patients undergoing hyperbaric therapy or in long-term ICU patients.

How do you correct hypoxemia?

The primary treatment for hypoxemia involves increasing the oxygen level in the bloodstream. This is typically achieved through the following remedies:

Five remedies to correct hypoxemia

1. Supplemental oxygen:

• Administering oxygen through a nasal cannula, face mask or mechanical ventilation can promptly increase oxygen levels in the blood, alleviating hypoxemia.
• Hyperbaric oxygen therapy (HBOT) is employed in cases of severe hypoxemia or when conventional oxygen therapy is insufficient. HBOT involves breathing pure oxygen in a pressurized chamber, facilitating the delivery of oxygen to tissues.

2. Mechanical ventilation:

• In severe cases of hypoxemia or respiratory failure, mechanical ventilation may be required to support breathing and maintain adequate oxygenation.

3. Addressing underlying conditions:

• Treating lung disorders such as chronic obstructive pulmonary disease (COPD), pneumonia, pulmonary embolism, COVID-19 or asthma may necessitate specific treatments to improve lung function and oxygen exchange.
• Managing cardiac conditions such as heart failure, coronary artery disease or arrhythmias may contribute to hypoxemia. Proper management of these conditions is essential to optimize cardiac function and oxygen delivery.

4. Medications:

• Depending on the underlying cause, medications such as bronchodilators, corticosteroids, diuretics, or anticoagulants may be prescribed to alleviate symptoms and improve oxygenation.

5. Lifestyle modifications:

• Smoking cessation, maintaining a healthy weight, regular exercise, and proper nutrition can contribute to overall lung health and may help manage underlying conditions contributing to hypoxemia.

What’s the life expectancy of someone with hypoxemia?

Life expectancy for someone with hypoxemia depends on the severity of the condition and the underlying cause. In severe cases, such as acute respiratory distress syndrome, healthcare providers may use a ventilator to assist with breathing.

Long-term oxygen therapy can be effective in managing hypoxemia in some patients, such as those with severe hypoxemia due to chronic obstructive pulmonary disease (COPD). However, in real-life settings, patients under long-term oxygen therapy have been found to have poor prognosis and increased risk of death.

Hypoxemia itself can be life-threatening if left untreated. Prompt and appropriate management can significantly improve outcomes and quality of life. But chronic hypoxemia due to conditions such as severe COPD or advanced heart failure may impact long-term prognosis.

To improve overall prognosis and quality of life, people with hypoxemia should work closely with healthcare providers to optimize treatment and address underlying health concerns.

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What are complications of hypoxia?

Hypoxia causes decreased oxygenation of multiple organs such as the brain, liver, kidneys, etc., damaging them, and ultimately leading to organ failure. It can potentially lead to death. Hypoxia during pregnancy may also result in fetal death. Hypoxia in newborns is associated with a high mortality rate.

If hypoxia is identified and treated early, patients can recover without any complications.

What is the lowest blood oxygen level before death?

The lowest blood oxygen level before death can vary depending on several factors, including a person's overall health, age, underlying medical conditions, and the rate at which oxygen levels decline.

An SpO2 level of 92 percent is considered the lowest clinically acceptable level by established norms of clinical practice at any age, except in cases of chronic lung disease, where it is 88 percent. Death can occur due to hypoxemia at any level less than 88 percent.

• In general, sustained blood oxygen levels below 80 to 85 percent can be life-threatening and may lead to severe complications or death if not promptly addressed.
• If the oxygen level falls below 85 percent, serious symptoms of hypoxia can occur, posing a risk of serious injury or death.
• In oxygen levels below 65 percent, mental impairment can occur.
• If the oxygen level falls below 55 percent, consciousness loss may lead to death.
• At an oxygen level of 10 percent, an individual may have only minutes or seconds to survive.

The critical threshold for survival with low oxygen levels is influenced by factors such as altitude, heart and lung health, and the body's ability to receive sufficient oxygen for normal function. In cases of severe hypoxemia, immediate medical attention and oxygen therapy are crucial to prevent fatal outcomes.

Can hypoxia and hypoxemia be prevented?

The conditions that cause hypoxia and hypoxemia may be prevented in some individuals by avoiding circ*mstances that reduce the oxygen concentration in the environment or by providing oxygen via nasal cannula or oxygen masks before hypoxia and/or hypoxemia develop.

This can be done by recognizing individuals who tend to develop hypoxia and/or hypoxemia and providing them oxygen if they develop any early symptoms.

Moreover, some medications can provide prevention and/or relief from hypoxia/hypoxemia symptoms that are due to certain medical conditions such as asthma.

What is respiratory failure with hypoxia?

Respiratory failure with hypoxia, also known as hypoxemic respiratory failure, is a serious medical condition where the blood lacks sufficient oxygen to meet the body’s needs. This can be due to various reasons:

• Lung diseases such as pneumonia, chronic obstructive pulmonary disease (COPD), lung infection, acute respiratory distress syndrome, and other conditions that impair the lungs’ ability to oxygenate the blood properly
• Neuromuscular disorders such as muscular dystrophy trauma to the chest or drug overdose

In respiratory failure with hypoxia, the lungs may not be able to efficiently exchange oxygen and carbon dioxide, leading to inadequate oxygenation of the blood. This can result in the following symptoms:

• Shortness of breath
• Rapid breathing
• Confusion
• Bluish discoloration of the skin (cyanosis)

In severe cases, it can lead to organ damage or even death if not promptly treated.

Treatment for this condition may involve:

• Supplemental oxygen
• Mechanical ventilation to support breathing
• Addressing the underlying cause (such as treating pneumonia or administering medications for COPD)
• Lung transplantation, in some cases

Respiratory failure with hypoxia is a serious condition. Prompt diagnosis and treatment are crucial to prevent further organ damage and improve outcomes.

From

Barker SJ, Shah NK. "Four Types of Pulse Oximeters Accurately Detect Hypoxia During Low Perfusion and Motion."