Pulse oximetry

Pulse oximeter is a device used in measuring the oxygen levels in the blood using indirect, non-invasive, light based technology. It is simple, painless, and relatively inexpensive test that can be done by the patient, and in most situations, corresponds to the blood oxygen concentrations.

Error creating thumbnail:

OxyWatch C20 Pulse Oximeter

Detection of hypoxia

Low oxygen levels in the blood are called hypoxia and it can be an early warning sign that medical intervention is needed.

Method

Pulse oximetry is the method that measures the percentage of blood hemoglobin carrying oxygen.

Vital sign

Many consider it a vital sign, like blood pressure.

how a pulse oximeter works

How is it done?

A beam of red light is passed through the fingertip by using a device called a pulse oximeter. Oxygen level, or saturation (SpO2), is determined by measuring how much light is absorbed as it passes through the fingertip.

Normal levels

• Normal SpO2 is usually at least 95%.
• Some patients with chronic lung disease or sleep apnea can have normal levels around 90%.

When to contact healthcare professional?

A medical professional should be consulted for SpO2 reading below baseline or per facility protocol.

Use during COVID

• Pulse oximetry is used as a screening tool in those that are diagnosed with COVID-19 but are not in a hospital or healthcare facility so that when there is a significant drop in oxygen (anything more than 3% of drop from baseline is a concern), the patients are encouraged to contact their healthcare provider.
• Contact a health care provider if a patient experiences shortness of breath or when measured SpO2 is <95%.
• CDC defines severe illness of COVID-19 in people who have respiratory frequency >30 breaths per minute, SpO2 <94% on room air at sea level (or, for patients with chronic hypoxemia, a decrease from baseline of >3%).

Treatment with oxygen

Supplemental oxygen or other treatments might be needed when the oxygen saturation drops below normal.

Confirm with arterial blood gas

Since pulse oximetry is not very specific test, confirmation should be done using arterial blood gas analysis or ABG.

Conditions causing low pulse oximeter readings

Asthma, heart disease, lung cancer, chronic obstructive pulmonary disease (COPD), the flu, and COVID-19 are some of the health issues that may cause oxygen levels to drop. When the levels are too low, we may need to take extra oxygen, known as oxygen therapy.

See also

• Arterial blood gas
• Capnography
• Integrated pulmonary index
• Respiratory monitoring
• Medical equipment
• Mechanical ventilation
• Oxygen sensor
• Oxygen saturation
• Photoplethysmogram, measuring of carbon dioxide (CO₂) in the respiratory gases
• Sleep apnea
• CO-oximeter

Pulse oximetry on Wikipedia

• Wikipedia's article on Pulse oximetry

Latest research

Latest articles - Pulse oximetry

• Most recent articles
• Ongoing trials

Frequently asked question on Pulse oximetry

• Have question on Pulse oximetry? Ask in the Question portal.
• FAQ's on Pulse oximetry
• What factors affect pulse oximetry readings?

Error creating thumbnail:

Pulse oximetry spectrum

• What are some conditions that can give a false pulse oximetry reading?

Carbon monoxide poisoning, Hypoperfusion due to congestive heart failure, vasoconstriction, incorrect sensor application, methemoglobinemia.

• What are the 2 readings on a pulse oximeter?

Oxygen saturation and pulse are the two readings on pulse oximeter

• What is the normal range of pulse oximetry?

Normal varies based on a person's medical condition but most people have a pulse oximeter readings of above 95. Those with COPD or other chronic lung conditions may have a slightly lower oxygen saturations of about 90. Since the pulse oximeter is a logarithmic scale, even a small change in the oxygen saturation may mean significant drop in actual oxygen levels in the blood.

• Why is my Oximeter not reading?

Check the proper application, check to see if it needs new batteries.

• Is it normal for spo2 to fluctuate?

Yes, normal pulse oximeter readings do fluctuate 2-3 points.

• Can stress affect oxygen levels?

Usually not to a significant degree.

• Can anxiety cause low oxygen levels?

Anxiety can lead to hyperventilation which in turn leads to an increase in pulse oximeter readings. However, since overbreathing leads also to driving out carbon dioxide, this can lead to a reflux slowing down of breathing after the initial overbreathing leading to lower oxygen saturations for a short period after the initial period of hyperventilation.

• What is the lowest oxygen level you can live with?

Normally, about 95% in most people, and about 90% in those that are hypoxic on a chronic basis such as those with COPD. Some COPD patients can live with oxygen saturations in the upper 80's although these patients should be evaluated for use of home oxygen therapy.

• Is 92 a good oxygen level?

It depends on the person. If the person has no underlying medical problems, 92 is considered low. If the person has COPD, this can be considered normal.

Help answer these questions

• How do you check oxygen level in oximeter?
• What is the first sign of hypoxia?
• What are the symptoms of not enough oxygen in the blood?
• What is the principle of pulse oximetry?
• What heart conditions cause low oxygen?

• UpToDate on Pulse oximetry