Pulse Oximetry: Uses, Readings, and How It Works

Written by Resurchify | Updated on: February 14, 2023

Pulse Oximetry: Uses, Readings, and How It Works

Oxygen saturation can be measured in several ways. This article will primarily focus on Pulse Oximetry, dig in now!

Pulse Oximetry is a test that is used for the measurement of the oxygen saturation or oxygen level of the blood. It is considered to be a painless and easy measure of how nicely oxygen is being transported to various parts of the body of a person further to his heart, such as the legs, the arms, etc. 

About Pulse Oximetry 

Pulse Oximetry, as provided above is a non-invasive procedure that helps in the effective measurement of the level of oxygen saturation of the blood. It can assist a person by rapidly detecting any change, even if they are very small, in the level of oxygen. Such levels tell whether or not blood is carrying oxygen efficiently to the extremities that are far from the heart. 

The probe or a pulse oximeter is a small device shaped like a clip that is placed on a particular part of the body, such as an ear lobe, finger (mostly), etc. This device makes use of light for measuring the concentration of oxygen in the blood in your body. Such information assists a healthcare provider to decide whether a person requires an extra amount of oxygen or not. 

Several medical professionals often tend to use them in a critical care setting such as a hospital or an emergency room. Various doctors, such as a pulmonologist, might use it in an office setting. A person can even consider using this at his home. 

When Might A Person Need Pulse Oximetry?

Pulse oximetry might be used to judge whether there exists enough oxygen in the blood. Such information is required in different types of situations. This may be used: 

  • After or during a procedure or surgery that used sedation 
  • To see how well a lung medicine is working for a person 
  • To check the ability of a person to handle an increased level of activities
  • To see if there is a requirement for a ventilator to help a person breathe or to see how effectively it is working for him 
  • To check if a person has several moments when he stops breathing while he is asleep (sleep apnea) 

This procedure is also used for checking or analyzing the health of a person suffering from any condition that tends to affect the oxygen level of the blood. This can include: 

  • Heart attack 
  • Chronic obstructive pulmonary disease (COPD)
  • Lung cancer 
  • Pneumonia 
  • Heart failure 
  • Anemia 
  • Asthma 

The healthcare provider might have other reasons to prove his theories regarding pulse oximetry and to further advise someone on pulse oximetry. 

What Are The Advantages And Disadvantages Of Using A Pulse Oximeter?

Pulse oximetry offers a plethora of advantages over the traditional methods used for measuring the oxygen levels of blood. Traditional methods, on the other hand, tend to involve drawing a sample of blood from an artery. It has been defined by people as a painful experience potentially for the patients and generally needs a minimum of 15 minutes to analyze the sample of the taken blood. Pulse oximetry provides immediate readings on the advantage. In addition to this, a pulse oximeter can be continuously used and can therefore monitor a person and the level of oxygen in his blood for a comparatively longer duration. 

At a similar time, pulse oximetry is proved to be less precise than a conventional method, say, for instance, arterial blood gas testing. Also, this technique fails to provide any information on the gases present in the blood (such as carbon dioxide) as much as the tests provide while measuring the blood directly. 

What Are The Risks Associated With Pulse Oximetry?

Every procedure is coupled with a set of risks. The probable risks of pulse oximetry are mentioned below: 

  • While following the procedure, if the probe ends up falling off the finger, earlobe, or toe of a person, the reading can be highly affected. 
  • The adhesive present in the probe might lead to skin irritation for many people. 

The risks faced by a person are considered to differ from one person to the other. This variation generally tends to depend on the general health of a person coupled with several other factors. A person can also consider visiting his healthcare provider to talk and consult about the risks that mostly tend to apply to him. Additionally, he can also talk to him about the concerns he might be facing as a result of the procedure. 

How Can A Person Be Ready To Undertake Pulse Oximetry?

The healthcare provider of a person will efficiently elucidate and explain the procedure and everything related to it without any technical jargon to him. The person, on the other hand, must ensure that he does not refrain from asking any questions that might come across his mind concerning the procedure. In case a finger probe is used for the technique, a person might be requested to remove the nail polish applied to the fingernail. 

Apart from this, there might exist other sets of instructions for the person to be given by his healthcare provider to get fit and ready for the procedure. 

How To Take A Correct Reading With A Pulse Oximeter?

Pulse oximetry might be fruitful in any setting, whether it is inpatient or outpatient. In a few cases, the doctor of a person might recommend that he has a pulse oximeter in his possession to be used at his home. 

For taking a reading with the help of a pulse oximeter, a person will have to keep the following steps or points in mind: 

  • Start by removing any nail polish off your finger or any piece of jewelry if a person is measuring from such a location. 
  • Secondly, it must be ensured that his hand is relaxed, below his heart level, and relaxed if the device is attached at such a location. 
  • Thirdly, he is required to place the device on his toe, finger, or earlobe. 
  • Fourthly, he ought to keep the device on for as long as required to effectively and correctly monitor the oxygen saturation of his blood and his pulse. 
  • Once the test is successfully over, the device must be removed. 

In this procedure, a small beam of light is passed through the blood in the finger of the person to measure the amount of oxygen present in it. As per the British Lung Foundation, a pulse oximeter can perform this function by measuring any change whatsoever in the absorption of light in deoxygenated or oxygenated blood. 

The procedure is completely painless and performed with the pulse oximeter to gain cognizance regarding the oxygen saturation level of the blood coupled with the heart rate of a person. 

Readings Post A Pulse Oximetry

A pulse oximetry test is an estimation of the level of blood oxygen, but it can be very precise. This is especially correct when high-quality equipment is used which is generally found in a hospital setting or a medical office. With such a piece of equipment, a medical professional can easily carry out such tests as accurately as possible. 

The Food and Drug Administration generally needs a prescription oximeter to provide correct results with an accurate range of about 4 to 6 percent approximately. Typically, as per the American Thoracic Society, more or about 89 percent of the blood of a person should carry oxygen with it. This is considered the saturation level of oxygen required to keep the cells of the body healthy. 

Having the blood oxygen saturation level below such a level temporarily might not cause damage. But consistent or repeated instances of a lowered level of oxygen saturation might be damaging. An oxygen saturation level ranging to about 95 percent is generally taken to be typical for a healthy person. Simultaneously, a level of 92 percent or any lower than that can potentially indicate hypoxemia. Hypoxemia is a condition wherein the oxygen level of the blood ends up becoming seriously low. 

Numerous factors tend to affect the readings given by a pulse oximeter; this also includes the skin tone of a person. A report given in 2020 compared the rate of accuracy of a pulse oximetry test and the blood gas measurements to detect hypoxemia in a white and black patient. Researchers have also discovered that in the case of black patients, there were about three times more cases of a pulse oximetry test failing to detect hypoxemia while a blood gas measurement detected it successfully. Such a test was developed without considering skin tones and the diversity in people. It was, therefore, concluded by the authors that more research is required to comprehend and correct such a racial bias. 

What Happens At The Time Of Pulse Oximetry?

A person might get his procedure done as an outpatient. This typically means that he goes back home on the same day, or it may be performed as a part of a comparatively longer stay at a hospital. How this procedure is done might vary. It directly depends on the condition and the methods used by the healthcare provider. 

In various cases, pulse oximetry tends to follow the following process: 

  • A probe resembling the shape of a clip is placed on the earlobe or a finger. If not, a probe may be placed on the finger or forehead of a person with a sticky adhesive. 
  • For ongoing monitoring, the probe is left on the site. 
  • It might otherwise be used for taking a single reading.
  • The test ends with the removal of the probe. 

Understanding The Results Of A Pulse Oximetry

A pulse oximeter examines a rapid measurement, without the use of any needle or a blood sample, of the oxygen saturation level of the body. The amount measured is then showcased on the screen which reflects the saturation of oxygen along with red blood cells in the blood. Such a discovered number provides a doctor or a nurse with a rough idea about the treatment suitable for a person. It may further help in the determination of the requirement for supplemental oxygen. 

What Tends To Happen Post A Pulse Oximetry?

Once a person is done with the test, his doctor will provide him with the readings immediately. This will help in the determination of the fact as to whether or not any other treatment or testing is required. Say, for instance, if a person is evaluating the successfulness of his oxygen supplementation therapy, reading on a comparatively lower side might conclude a need for an extra level of oxygen. 

A person’s doctor will then be capable of cognizing him of the next steps. If he is using pulse oximetry in the comfort of his home, the doctor will let him know the frequency to take the readings and what is to be done if they go below or above a certain level. 

A person can head back to his home after the test is completed unless he is in the hospital for any other reason. He can get back to his normal activities and diet as per the instructions of his healthcare provider. He might also be provided with other instructions by him post the procedure. 

Potential Diagnosis 

A conventional pulse oximeter diagnoses hypoxia. However, certain pulse oximeters have witnessed recent developments making them assessable to other parameters such as total hemoglobin, carboxyhemoglobin and methemoglobin levels, oxygen level above a saturation of 100%, etc. With the further display of the activity parameters of the pulse wave, respiratory rate and volume status in an intubated patient can be displayed in various oximeters by taking a look at the pulse pressure variation with a respiratory cycle. 

Complications Concerning Pulse Oximeters

A pulse oximeter is well-tolerated equipment and is used by people from every age group, ranging from geriatrics to the neonate population. The transfer of energy is low and while a heat blister with high usage of several sensors is highly possible, a lot of complaints tend to be the result of an allergic reaction to the medical adhesive properties of a single-use sensor or the adhesives. Pressure points from a clip sensor are also possible but rare and can be minimized with the use of an adhesive probe. 

Education And Safety Of The Patient

No special education is generally needed by a person beyond the following: 

  • Explaining that the sensor is used to measure the level of oxygen in the blood of the patient 
  • That the risk of such monitors is low 
  • To report any discomfort, uneasiness, or tension to a patient care provider 

Accuracy Of A Pulse Oximeter

The oxygen level from such equipment is highly accurate. Most pulse oximeters provide a reading which is either 2% over or 2% under what the saturation would be if it was obtained via an arterial blood gas. Say, for instance, if the oxygen saturation level of a person reads 92% on a pulse oximeter, it might be somewhere around 90% to 94% tentatively. For a good reading, a person is required to allow a few seconds for the pulse oximeter to adequately capture his pulsations. 

Several factors might end up reducing the accuracy of a reading given by a pulse oximeter, they are: 

  • Cold hands 
  • Skin pigmentation 

Skin pigment can impact the accuracy of the readings given by a pulse oximeter. Several studies have concluded that a person with comparatively darker skin pigments might miss oxygen saturations below normal. A person with a darker skin tone must consider asking his provider about the accuracy and correctness of his oximetry readings. 

  • Movement 
  • Applied nail polish (green, black, or blue) 
  • Artificial nails 
  • Smoking 

If a person smokes, the reading given by the oximeter might be higher than his oxygen saturation level as smoking tends to increase the level of carbon monoxide in the blood. The oximeter fails to judge the difference between oxygen and carbon monoxide gas. 

  • Low oxygen saturation level (below 80%) 
  • Thicker skin than normal 

The results of the oximeters must always be discussed by a person with his provider to check if they even make sense. In addition, this also helps to know what can be done with such information before any medical decision is made. 

When Should A Pulse Oximeter Be Used?

If a person has been prescribed to use a pulse oximeter by his healthcare provider, he should ask him if they want him to use it or not for monitoring his blood oxygen level. He should also ask him when he should consider changing the rate of flow on his supplemental and the reading at which he shall consider seeking urgent medical attention. 

Times When The Reading Of An Oximeter Might Be Helpful

When a person is a first prescribed oxygen

This assists his healthcare provider to know whether and how his oxygen saturation level has witnessed a change while performing any activity at home. 

After or during exercising

Like a car needs gas, the body also requires oxygen while a person is moving. The oxygen saturation of a person might be checked at the time of activity to check if he has low oxygen. His healthcare provider will decide with him about the steps to be taken further if he is having oxygen problems while exercising. 

While traveling or flying to a high-altitude location 

The supplemental oxygen level might increase in such a situation. 

How Can A Person Get A Perfect Reading With A Pulse Oximeter?

A pulse oximeter measures the percentage of oxygen carried by the blood and the blood saturation. To obtain a perfect reading with the help of an oximeter, a person must ensure that enough blood is flowing to the finger and hand in which he is wearing the device. Therefore, the best reading can be achieved when the hand of a person is relaxed, warm, and placed below the level of his heart. If he successfully follows the guidance and his pulse oximeter seems to provide an inaccurate reading, there might be an issue with the probe he is using. A person can bring his oximeter to the office of his healthcare provider or the equipment company to get it checked for a high rate of accuracy.

Home Usage 

Some people tend to use a pulse oximeter in the comfort of their homes, particularly with the advent of the COVID-19 pandemic. As far as home pulse oximeters are concerned, there generally exists two types of pedometers: 

  • Over-the-counter oximeter 
  • Prescription oximeter 

Several insurance companies would generally invest in a pulse oximeter. Check with the provider. Additionally, a person can consider following the guiding principles provided by his doctor and the manufacturer of the device on when and how to take a reading.

He can also assist in the improvement of his chances of getting a more useful and accurate reading if he:

  • Ensures that his hand is warm, relaxed, and below the level of his heart.
  • Remove the polish on the nails of the finger he is reading.
  • The device must be placed exactly as per the instructions the suggestions provided by the manufacturer.
  • A steady number must be looked at by a person, the numbers might play around for several seconds.
  • The track of the levels coupled with the time and date must be kept track of to provide the doctor a sense of how his numbers are changing with time. Lower levels with time generally suggest the presence of a serious health problem.

Recommendations To A Healthcare Provider

  • Be cognized that the existence of a plethora of factors can end up affecting the accuracy of the reading given by the pulse oximeter, such as skin pigmentation, skin temperatures, use of fingernail polish, poor circulation, skin thickness, current use of tobacco, etc.
  • Refer to the labeling on the device or the website of the manufacturer to gain a better understanding of the accuracy of a brand of the sensor and a pulse oximeter. Several brands of pulse oximeters and even a few sensors might possess a different level of accuracy. A pulse oximeter is considered the least accurate when the saturation level of oxygen is less than 80%.
  • Consider the limitations of accuracy while you are using a pulse oximeter to help the treatment and diagnosis decisions.


Pulse oximetry, as a takeaway, is a non-invasive, painless, and quick test. It fails to involve any risk associated with it, apart from potential irritation of skin by the adhesive used in several probes. It is considered a comparatively safer test as it does not involve any real risk per se. But the sticky material on the probe might lead to skin irritation. If a person or his nurse does not put the sensor correctly using the right method, he might not attain accuracy in the results. One should visit a doctor in case of any concerns or questions.



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