Pulse oximetry is a routine procedure to assess your oxygen saturation levels (SpO2)+. SpO2 level measures the oxygen in the blood and the effectiveness in reaching the extremities like the arm and legs.

Health practitioners use different kinds of pulse oximeters on various body parts. But the fingertip pulse oximeter has proved ideal in clinical experiments due to its high accuracy and ease of use.

A fingertip pulse oximeter has a photoelectric sensor that allows it to display your finger’s pulse rate and oxygen saturation levels. It’s portable, user-friendly, and requires minimal power to function. Fingertip pulse oximeters are common today and can be found in pharmacies like CVS and Walgreens, among others. According to research, pulse oximetry shows high accuracy with SpO2 greater than 90% and can be effectively used in place of arterial blood gas.

A fingertip pulse oximeter is helpful in both inpatient and outpatient care. Your physician may also recommend you have one at home to monitor your oxygen levels constantly.

The Measurement Principle of Fingertip Pulse Oximetry

A functioning fingertip pulse oximeter follows the Lambert-Beer Law based on spectrum absorption characteristics of reductive hemoglobin (RHb) and Oxyhemoglobin (HbO2) in red and near-infrared zones.

The fingertip pulse scanner has two beams with different wavelengths, 660nm red and 940nm near-infrared light. After clamping the pulse oximeter on the finger, the SpO2 reading is obtained through photosensitive elements focused on the nail tip, and the results are shown on the display monitor.

What Should the Reading be on a Fingertip Pulse Oximeter?

A healthy individual’s fingertip oxygen saturation ranges from 95% to 100%. Health guidelines recommend blood gas assessment for any reading below 90% in case oxygen therapy is necessary.

A pulse reading is essential in managing medical conditions, like asthma, chronic obstructive pulmonary disease (COPD), lung cancer, COVID-19, or heart failure, among others.

How to Use a Fingertip Pulse Oximeter
Remove finger polish, fake nails, and any jewelry before taking the measurements.
Assume a seated position and relax.
Make sure your hand is warm and rested below heart level.
Clamp the device onto the finger and take the reading.
Wait until the pulse oximeter stops changing and displays a steady number.
The reading displays after 4–6 heartbeats.
Test twice for certainty.

If you are taking the test at home, it is essential to note whether the oxygen levels are steady or decreased compared to earlier readings. Don’t rely on your fingertip pulse oximeter to assess your general health.

When monitoring blood oxygen levels at home, pay attention to additional signs of low oxygen:

Bluish discoloration on the lips, extremities, and face
Shortness of breath or difficulty breathing
Chest congestion and tightness
Rapid pulse rate
General discomfort

Keep in mind that low oxygen levels can be accompanied by some or all of the signs and symptoms listed above or show none.

Note: Don’t self-diagnose. Instead, visit a healthcare provider for the diagnosis of medical conditions.

Uses and Benefits of a Fingertip Pulse Oximeter

A finger pulse oximeter is beneficial to both patients and healthcare providers. Below are some of its uses:

Assessing whether specific procedures are safe in patients with cardiovascular or respiratory problems
Monitoring a patient’s oxygen levels during a stress test
Monitoring oxygen saturation levels during and after oxygen therapy
Providing feedback on breathing interventions and treatments administered like ventilation
Tracking the oxygen levels of a patient under general anesthesia
Assessing the adverse effects of medication that can potentially cause low oxygen saturation or difficulty in breathing, such as opioid medications

Benefits of a Fingertip Pulse Oximeter

Fingertip pulse oximeters are widely used in medical facilities and patients’ homes. They make work easier by providing accurate readings in no time, which is helpful in emergencies.

Some of the benefits of a fingertip pulse oximeter include:

Simple and easy to use for everyone
Portable and light
Painless and non-invasive test
Monitoring patients at home
Accurate reading in a matter of seconds
Alerting caregivers in case of unexpected low blood oxygen saturation levels
Easy to monitor oxygen levels over some time
Handy for patients with conditions like sleep apnea, which require continuous oxygen assessment

Necessary Precautions When Using a Fingertip Pulse Oximeter

Here are some of the precautions to take when using a fingertip pulse oximeter:
Don’t have a fingertip pulse oximeter when taking a CT scan or MRI.
Ensure the pulse reading is correct first to verify the SpO2 measurements are accurate.
Avoid using fingertip pulse oximeters when alerts are necessary, as most brands lack an alarm.
Avoid using a fingertip pulse oximeter in an explosive environment or near combustible materials.
Use a fingertip pulse oximeter only as a supplementary evaluation method alongside other methods, like clinical assessment and symptoms, to make a diagnosis.
Ensure the sensor alignment and skin integrity to align for accurate measurements.
Clamp the device for a maximum of eight minutes. The device should give a steady reading after 4–6 heartbeats.
Avoid autoclaving, ethylene oxide sterilization, and liquid sterilization of the device.
Abide by the recycling laws when disposing of the gadget or its components.

Pulse Oximeter Error Margin

Pulse oximeter readings might vary somewhat from time to time, which is normal. However, the error margin is about 2% or less. This means that your blood oxygenation level may range from 95% to 99% if the reading shows 97%. It is possible, however, for the measurements to deviate significantly from this typical deviation range owing to certain factors discussed in the next section.

Causes of Inaccurate Measurements

Pulse oximeters have a range of limitations, which can contribute to incorrect readings. The following may be reasons for inaccurate readings:

Excessive Movement

Excessive movement by the individual taking the test is one of the most common reasons for false pulse oximeter readings. For an accurate measurement of SpO2 levels, pulse oximeters must be in a stable position. This can be especially true if the individual moves from a dimly lit room to one with brighter lighting (or vice versa) or if the pulse oximeter falls off or moves around.

Improper Placement

Misusing the pulse oximeter might result in false values. When placed on an enlarged finger, excessive pressure may be exerted on that particular spot, reducing blood flow and resulting in inaccurate results. There are proper guidelines for using a pulse oximeter as stipulated by the FDA.

Nail Polish

There’s no question that this one also falls under human error. Light is absorbed by nail polish because it is so thick. Therefore, getting good pulse oximeter readings on a finger with nail polish is almost impossible.

Skin Pigmentation

Skin pigmentation is an additional variable that can alter the oximetry readings. Darker skin takes in more light than a lighter. Since pulse oximeters rely on light to determine the amount of oxygen in the blood, inaccurate results are likely from an excessive amount of light being sucked up by the skin. People with darker complexion might be at risk, particularly if they already suffer from low amounts of oxygen in the blood.

Carbon Monoxide

Another factor that might create erroneous results is carbon monoxide. Carbon monoxide molecules bind to hemoglobin and replace oxygen molecules, resulting in a decrease in oxygen levels. An oximeter can’t tell the difference. Suppose your hemoglobin has 82% oxygen and 13% carbon monoxide; the result would be 95%.

Insufficient Blood Volume

Another thing that can throw off your readings is if your blood volume is too low. It is impossible to accurately measure blood flow with the pulse oximeter when you’re suffering from a reduced blood flow.

Electromagnetic Signals

Electromagnetic transmissions from other electrical equipment can potentially impact pulse oximeter readings.

Does Monitoring SpO2 Levels at Home Present Any Risks?

Although monitoring SpO2 levels at home can keep you safe, there are risks involved, especially if you have a faulty device. Faulty readings may cause false alarms or give you a false sense of confidence even when you’re at risk.

If you or someone else in your home has an extremely low reading, try testing a healthy individual to ensure that the reading is accurate before addressing the issue with your primary physician.

Bottom Line

The pulse oximetry test is brief, does not involve intrusive procedures, and does not cause discomfort. Therefore, there are few to no risks associated with it, with the possible exception of skin irritation caused by the adhesives used in some probes. Fingertip pulse oximeters are commonly used in hospital and home settings and have revolutionized the world of health management.

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