Hypoxia is a condition or state in which the supply of oxygen is insufficient for normal life functions; hypoxemia is a condition or state where there is a low arterial oxygen supply -- in some publications these terms are used interchangeably. In general patients' hypoxemia, the blood oxygen level is about 92% or lower.
Causes of Hypoxemia
A variety of conditions and circumstances can interfere with the body’s ability to deliver normal levels of oxygen to the blood. Some of the most common causes of hypoxemia include heart conditions, including heart defects, congenital heart defects in children , and congenital heart disease in adults.
Lung conditions include asthma, emphysema, bronchitis, pneumonia, pneumothorax (collapsed lung), pulmonary edema (excess fluid in the lungs), pulmonary embolism (blood clot in an artery in the lung) , and pulmonary fibrosis (scarred and damaged lungs). Other conditions include locations of high altitudes, where oxygen in the air is lower, strong pain medications, or other problems that slow breathing and sleep apnea (impaired breathing during sleep).
Ventilation-perfusion Mismatch.
Alveolar ventilation is normally between four and six liters per minute. This physiological process is responsible for bringing oxygen to and removing carbon dioxide from the lungs.
Mixed venous blood carries carbon dioxide into the lungs and takes up alveolar oxygen. The alveolar partial pressures of oxygen and carbon dioxide are therefore determined by the relationship between alveolar ventilation and perfusion.
An ideal ratio of ventilation to perfusion, which is also known as the V/Q ratio, is approximately one. If this ratio is less than one, but not zero, hypoxemia caused by this mechanism can develop. An abnormal V/Q ratio in various regions of the lungs is the most common cause of hypoxemia in all types of patients.
This type of hypoxemia responds beneficially to oxygen supplementation given either by face mask or nasal prongs. Oxygen therapy is highly required in COVID-19 patients
Symptoms
Symptoms of hypoxia and/or hypoxemia may be acute or chronic and vary in intensity from mild to severe depending on the severity of the condition.
Common acute symptoms are shortness of breath, rapid breathing, a fast heart rate, headache, coughing wheezing, bluish color in skin, fingernails, and lips
Severe symptoms include: the inability to communicate, confusion possible coma or other associated symptoms also may be present.
Hypoxia or hypoxemia symptoms in children may be mouth breathing and drooling.
Pulse Oximetry
Normal arterial oxygen is approximately 75 to 100 millimeters of mercury (mm Hg). Values under 60 mm Hg usually indicate the need for supplemental oxygen. Normal pulse oximeter readings usually range from 95 to 100 percent. Values under 90 percent are considered low.
The Coronavirus Disease 2019 (COVID-19) pandemic has caused an increase in the use of pulse oximeters.
A pulse oximeter is a small, non-invasive, and painless device that measures the oxygen level (oxygen saturation) of the blood. The pulse oximeter can thus tell oxygen saturation levels as well as heart rate.
The device shows how well oxygen is being sent to those parts of your body furthest from your heart, such as the arms and legs. The small clip-like device is fixed on a finger, or earlobe depending on the oximeter being used. It passes small beams of light through the blood in the finger which measures the level of oxygen. It measures the light absorption changes in oxygenated or deoxygenated blood.
Although pulse oximetry is useful for estimating blood oxygen levels, pulse oximeters have limitations and risk of inaccuracy under certain circumstances that should be considered. Patients with conditions such as COVID-19 who monitor their condition at home should pay attention to all signs and symptoms of their condition and communicate any concerns to their health care provider.
They have to follow the health care provider’s recommendations about when and how often to check oxygen levels.
Multiple factors can affect the accuracy of a pulse oximeter reading, such as poor circulation, skin pigmentation, skin thickness, skin temperature, current tobacco use, and use of fingernail polish. To get the best reading from a pulse oximeter: follow the manufacturer’s instructions for use.When placing the oximeter on your finger, make sure your hand is warm, date and time of the reading so you can easily track changes and report these to your health care provider.
Can Hypoxemia be Prevented?
There are steps you can take to prevent hypoxemia from returning after treatment. To increase the oxygen levels in the blood, it may be recommended to practice
deep breathing exercises and mild exercises such as walking or yoga, eat a healthy diet , drink plenty of water and quit smoking.
For asthmatics, the best way to prevent hypoxia is to keep your asthma under control, every day. Stick with your asthma treatment plan.
Take your medicine to help prevent flares and the need to use your rescue inhaler.
Eat right and stay active.
Know your asthma triggers, and find ways to avoid them.
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