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Hypoxemia - Types, Symptoms, Diagnosis, Treatment, and Complications

Published on Feb 20, 2021   -  4 min read


Hypoxemia is the medical term for low oxygen levels in the blood. Know the symptoms, causes, consequences, and treatment options when blood oxygen falls below a certain level.



Oxygen is transferred to various organs and tissues of the body via the blood. When the oxygen levels of blood fall below the required amount, it is called hypoxemia. There are various causes for this condition like asthma, COPD, pneumonia, and recently, COVID-19, etc. It is a serious condition that requires immediate medical attention. This article will cover details about this condition.

What Is The Difference Between Hypoxia and Hypoxemia?

There is a major difference between hypoxia and hypoxemia. Hypoxia is a condition where there is a low level of oxygen present in the body tissue. In contrast, hypoxemia is a condition where there is a decreased oxygen level in the blood. It is rare for the two to occur together, but sometimes it may happen. Although, it is interesting to note that usually, if hypoxemia is there, hypoxia is suggested.

What Are The Types?

There are many types of hypoxemia, and they are classified based on the causative mechanism or pathophysiology. Following are the types:

1) Ventilation-Perfusion Mismatch

This type is the most common. The supply of oxygen to the lungs is called ventilation, and the supply of blood to the lungs is called perfusion. These two measures are usually calculated using a ratio called a V/Q ratio. The values are usually in slight variation, but when there is a large variation, it can lead to certain problems. The following two can be the major causative factors for such a variation:

2) Shunt

The common mechanism between lungs and heart is that the blood carrying carbon dioxide enters the right side of the heart and then reaches the lungs and gets enough oxygen to travel to various tissues from the heart and supply it. But in this hypoxemia, the blood tends to enter the heart on the left side without taking oxygen from the lungs.

3) Impairment of the Diffusion Process

In this type of hypoxemia, the blood getting combined with or diffused into the blood is affected.

4) Hypoventilation

This is a condition where oxygen is taken at a slow rate. Hence, there will be an increased level of carbon dioxide in the blood than fewer levels of oxygen.

5) Low Levels of Oxygen in the Environment

People living in higher altitudes face this type of hypoxemia as there is a very low level of oxygen in the environment.

How Is It Caused?

Many conditions can cause it, which are as follows:

  1. ARDS: Acute Respiratory Syndrome.

  2. Asthma.

  3. Anemia.

  4. A lung that has collapsed.

  5. Pulmonary embolism.

  6. COPD.

  7. Congenital heart diseases.

  8. COVID-19.

  9. Increased altitudes.

  10. Interstitial lung disease.

  11. Certain medications.

  12. Sleep apnea.

  13. Pneumonia.

  14. Scarring in the lungs.

Also, it is important to know that hypoxemia can be indicative of some other serious condition like respiratory failure.

Can Newborn Face Hypoxemia?

Yes, hypoxemia can be observed in newborns sometimes, especially in those with congenital heart diseases. The level of oxygen present in the blood is used to check for such defects. Preterm infants are at risk of getting hypoxemia, especially if mechanical ventilators are used in them.

What Are The Symptoms Of Hypoxemia?

A patient with hypoxemia can have the following symptoms:

1. Difficulty in breathing or shortness of breath.

2. Headache

3. Increased heartbeat

4. Wheezing or cough

5. Confusion

6. Disorientation

7. Cyanosis is bluish discoloration of skin, lips, mucous membrane, and fingernails

How Can It Be Diagnosed?

When you visit your physician, initially, your personal history and medical history will be taken along with the symptoms you are facing. Then a physical examination will be carried out where the heart and lungs will be checked. Also, the skin, fingernails, and/or lips may be checked for any discoloration. Some additional tests may be carried out to assess the level of oxygen and breathing, which are as follows:

  1. Pulse oximetry.

  2. Breathing tests using a machine.

  3. Arterial blood gas test.

How Can It Be Treated?

As the level of oxygen is lowered in hypoxemia, the main objective of the treatment is to raise the level of oxygen and bring it back to normal levels. Oxygen therapy can be used to treat this condition. In this, an oxygen mask or a small tube that is clipped to the nose is used to provide oxygen to the patient. If the cause of hypoxemia is an underlying condition, then it is important to cure or manage that condition along with supplementary oxygen (if required).

Are There Any Complications?

Oxygen is a very important thing for the survival of the tissues and organs of the body. Hence, if the levels of oxygen are reduced, then it can affect the vital organs like the heart, brain, etc., and if hypoxemia is not treated, then it may also become fatal. If you have shortness of breath or difficulty breathing, it is important to get a consultation from your physician as soon as possible.

COVID-19 and Hypoxemia:

As we are facing a pandemic right now, one of the symptoms of this condition is difficulty in breathing or shortness of breath, and pneumonia can occur. Hence, hypoxemia becomes an important topic of concern during this COVID-era.


Hypoxemia is a medical condition characterized by decreased oxygen levels and can be due to various causes. It can be managed, but if it is not treated properly, it can prove to be fatal. It is important to consult your doctor in case you face any of the symptoms mentioned in the article. Online medical platforms have made this task easy as COVID-19 can be one of its causes, and also, social distancing, lockdowns, etc., is hampering in-person consultation. Hence, consult a specialist or physician online through this platform.

Frequently Asked Questions


What Are the Causes of Hypoxemia?

The important causes of hypoxemia are:
- Pneumonia.
- Pulmonary edema.
- Pulmonary embolism.
- Pulmonary fibrosis.
- Acute respiratory distress syndrome.
- Aspiration.
- Lung collapse.
- Acute asthma.
- Pneumothorax.
- Pulmonary contusion (blunt chest trauma).
- Emphysema.


How Does Hypoxia Initially Start?

Hypoxia may be acute, chronic, or acute on chronic. It usually starts with shortness of breath followed by rapid breathing with an increased heart rate. They also experience wheezing, coughing, and sweating. This is because hypoxia is a state in which the oxygen supply is insufficient for normal life functions. Initially, they appear weak, unable to communicate, confused, and have rapid changes in skin color (from blue to cherry red). Sometimes in severe cases, it may result in death.


What Is Hypoxemia?

Hypoxemia is reduced arterial oxygen supply. In simple words, it is an abnormally low level of oxygen in the blood. Hypoxemia are of two types:
- Type 1 - Hypoxemia without hypercapnia (PaO2 < 8 kPa (<60 mm Hg) when breathing air).
- Type 2 - Hypoxemia with hypercapnia (PaCO2 > 6.5 kPa (>49 mm Hg) due to alveolar hypoventilation).


How Do You Manage Hypoxemia?

Increasing the oxygen intake and maintenance of the airway can help to reverse hypoxemia. Oxygen therapy is started to correct the hypoxemia, and oxygen is given to ensure adequate arterial oxygenation (SpO2 >90%), initially by face mask or nasal cannulae. Patients who need high concentrations of oxygen for more than a few hours should receive humidified oxygen. High concentrations of oxygen (40 to 60% by mask) will usually relieve hypoxia by increasing the oxygen in poorly ventilated lung units.


How Can We Compensate for Hypoxemia?

The reduced oxygen saturation of arterial blood results in cardiovascular system collapse, cyanosis, confusion, asterixis, and these can be compensated by delivering more blood to tissues for reduced oxygen delivery, which is sensed by oxygen-sensing mechanisms, such as carotid bodies. If no improvement, mechanical ventilation is needed.


How Can We Increase Oxygen in the Blood?

Blood is the fluid that supplies oxygen to our heart, lungs, organs, muscles, and other systems. Foods that increase oxygen in the blood are beetroot, strawberries, fatty fish, pomegranates, garlic, walnuts, orange, beans, meat, green vegetables.


What Is Nocturnal Hypoxemia?

Nocturnal hypoxia is also called transient nocturnal desaturation. It is defined as a temporary drop in oxygen saturation during sleep. Hypoxemia is a low level of oxygen in the blood. When the oxygen concentrations drop, but the carbon dioxide does not rise high, then it is nocturnal hypoxemia. For people with normal respiratory function, the oxygenation and ventilation remain the same. But sleep can lead to hypoxemia in patients with lung disease.


What Is Acute Hypoxemia?

Acute hypoxemia results from an increase in ventilation-perfusion mismatch within the lung, and this can be caused by almost any pulmonary disease. The most extreme form of mismatch is pulmonary shunting, which occurs when an area of the lung is not ventilated that is due to collapse or consolidation.


Does Hypoxemia Have an Impact on Erythropoiesis?

Reduction in oxygen tension results in a fall in arterial oxygen saturation. This varies widely between individuals, depending on the oxygen-hemoglobin dissociation. Acclimatization to hypoxemia at high altitude involves a shift in the oxygen-hemoglobin dissociation. More specifically, it is dependent on the erythropoiesis, hemoconcentration resulting from the hypoxic drive.


How to Assess Hypoxemia?

A. Respiratory pattern:
Inspiratory stridor - Typically caused by partial airway obstruction.
Tachypnoea - First indicator of critical illness.
Rapid shallow breathing - It indicates severe respiratory failure due to hypoxemia.
Prolonged expiratory efforts - It indicates severe bronchospasm due to hypoxemia.
B. Conscious level:
Worsening drowsiness - Indicates severe respiratory failure as a result of hypoxemia or hypercapnia.
C. Pulse oximetry:
Oxygen saturations - < 94% indicate arterial hypoxemia.
D. Arterial blood gases:
A sample of blood is taken from the artery, calculating the oxygen level. The lower value indicates more severe disease.


Is Hypoxia Harmful?

Generalized hypoxia occurs even in healthy individuals when they ascend to high altitude, resulting in:
- Acute mountain sickness - Increased cerebral blood flow and hence intracranial pressure.
- High-altitude cerebral edema (HACE) - It is rare and life-threatening.
- High-altitude pulmonary edema (HAPE) - It is a life-threatening condition that usually occurs in the first four days after ascent above 2500 m.


Does Hypoxemia Cause Hypertension?

Hypoxemia increases heart rate and results in higher blood pressure. It is associated with elevated sympathetic activity and hypertension in patients with chronic pulmonary obstructive disease.


What Are the Levels of Hypoxemia?

When the level goes below 75 mm Hg, the condition is generally termed hypoxemia. The levels under 60 mm Hg are considered very low and indicate the need for supplemental oxygen. Aircraft usually cruise at 10000 to 12000 meters, with the cabin pressurized to an equivalent of around 2400 meters. The summit of Everest is 8848 meters, and the highest permanent habitation is 5200 meters.

Article Resources

Last reviewed at:
20 Feb 2021  -  4 min read




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