How to Use the Pulse Oximeter

A device called a pulse oximeter is utilized to measure the level of oxygen in arterial blood, which is known as oxygen saturation or SpO2.

Pulse oximeters are employed in lung diseases to ensure the prompt detection of a dangerous drop in oxygen levels in the blood. Oxygen deficiency impacts all organs and tissues, particularly the heart and brain.

While pneumonia is a frequent complication of severe COVID-19, not all infected individuals require a pulse oximeter. In this article, we will discuss who might benefit from using this device, the proper usage to obtain precise results, and how to select the appropriate device.

Why do doctors use a pulse oximeter in coronavirus disease?

The pulse oximeter has become a crucial tool in 2020. In clinical settings, it enables doctors to promptly refer patients for hospitalization in cases where there is uncertainty. While hospitalized, pulse oximetry is utilized as part of a comprehensive diagnostic approach to determine whether a patient should be directed to a regular or intensive care unit, select an appropriate mode of oxygen therapy, and monitor its efficacy. During the rehabilitation phase, pulse oximetry can help assess progress in physical activity tolerance.

It is essential to monitor SpO2 because even in cases of severe oxygen deficiency due to COVID-19, it is often tolerated subjectively with ease, and sometimes even without noticeable symptoms.

Who needs to measure oxygen in the blood during coronavirus disease?

International clinical guidelines are continuously updated instructions for healthcare professionals on the proper treatment of COVID-19. These guidelines provide detailed information on who should measure oxygen levels in their blood. While the specifics of clinical recommendations may vary across different countries, they share similar key points. According to these guidelines, there is no benefit to using a pulse oximeter for individuals receiving COVID-19 treatment at home.

Most clinical guidelines recommend that patients with mild to moderate COVID-19 stay at home. The severity of the disease is determined by a doctor after examination. However, some individuals with COVID-19 experience a deterioration in their condition after the doctor leaves. Therefore, if a patient experiences a temperature above 38°C, shortness of breath, or blood pressure dropping below 90/60 mmHg, they should call their doctor as soon as possible to discuss next steps.

Monitoring these three symptoms can help catch a deterioration in condition. However, some specialists believe that a pulse oximeter may be useful as an additional means of self-monitoring.

Who really needs a pulse oximeter

Although a pulse oximeter is an essential diagnostic tool in the hands of a doctor, it is not advisable to recommend purchasing this device to anyone who has fallen ill or is afraid of contracting respiratory infections, including COVID-19.

Most individuals infected with COVID-19 experience mild symptoms and do not need to measure their SpO2 levels. Additionally, many people may not use the device correctly. Furthermore, even if a patient measures normal SpO2 readings, it does not eliminate the need for examination and questioning, just like reporting a decrease in saturation. Whether having a pulse oximeter at hand will make a patient feel more psychologically calm or become a cause of additional anxiety depends on the individual’s psychological characteristics.

A home personal pulse oximeter may potentially be beneficial in situations where:

• The patient has indications for hospitalization but is not admitted for some reason.
• The patient is at risk of experiencing a severe course of the disease.
• The patient or their family has established a trustworthy partnership with their primary care physician who can use the pulse oximetry data to adjust therapy and determine if hospitalization is necessary.

What do pulse oximeter readings mean?

The typical blood oxygen saturation range for healthy, non-smoking adults who reside at low elevations is considered to be 96-100% when measured by SpO2. However, if an individual lives in a high-altitude area, their normal SpO2 range may be slightly lower at 95-100%.

For individuals with mild COVID-19, SpO2 levels are expected to be within the normal range. In moderate cases, SpO2 levels often decrease to around 94-95%. If SpO2 levels dip below 95%, it is recommended to seek medical attention promptly. Patients in critical condition typically exhibit an SpO2 of 93% or less.

Checking your blood oxygen level is recommended at least twice daily, once in the morning and once in the evening.

To ensure accurate comparison of results, it is recommended to measure SpO2 on the same finger of the same hand, in the same position, and at the same time of day. It is worth noting that some reports indicate that SpO2 readings on the index finger of the same hand may be slightly lower than those on the middle finger. Likewise, readings may differ between fingers on different hands.

Which pulse oximeter readings should be monitored in the event of a Coronavirus infection?

A saturation level of 93% can easily go unnoticed as there may be no subjective feeling of shortness of breath, but rather severe weakness which can be mistaken for shortness of breath. A saturation level of 93% may not cause arousal or anxiety, and the patient may be too weak to even move to attend to basic needs like using the computer, phone, or going to the toilet. This sleepiness can worsen with time.

For patients under the age of 60, it is recommended to contact a doctor again if any of the following symptoms persist:

• A fever above 38°C
• Continuing weakness
• Saturation levels drop to 95% or below on the 5th-9th day of illness, after initially being at 98-99%

For patients over the age of 60, saturation levels may not be as reliable an indicator of health, so it is important to focus on symptoms such as weakness and fever. If any of these signs are observed, even if the oxygen saturation level is 95-96%, it is recommended to contact a doctor.

How a pulse oximeter works

All pulse oximeters operate on the same principle. They consist of red light sources – diodes, light-sensitive sensors, and a display monitor that shows the readings.

Typically, a pulse oximeter is designed to look like a clip that can be attached to a finger. The diodes and sensors are situated inside the clip, while the display is positioned outside. Once the clip is placed on the finger, light passes through it. As oxygenated arterial blood allows light to pass through differently than blood with low oxygen, the sensors detect any deviations from the norm and present the result on the screen.

The correct way to measure oxygen saturation is with a pulse oximeter.

To measure saturation, you should follow rules similar to measuring blood pressure:

• To begin, take a comfortable seated position and rest your hand on a flat surface. Ensure that your hand is warm and relaxed before proceeding.
• Next, place the pulse oximeter on your finger with the sensor positioned at the base of your nail. If the sensor is positioned on top of your nail, remove any nail polish to ensure an accurate reading. For the best results, it is also recommended to remove any artificial nails before taking the measurement.
• Once the pulse oximeter is properly positioned, try to remain still and avoid moving your finger during the measurement. Even slight movements can cause the light to hit the sensor at an incorrect angle, resulting in an inaccurate reading.
• Finally, wait for the signal sound to indicate that the measurement is complete.

A clip-style pulse oximeter can cause a reduction in oxygen saturation for people who are paralyzed. As such, they require a pulse oximeter that uses adhesive electrodes instead.

How to choose a pulse oximeter

There are three types of devices that are called pulse oximeters available in online stores. Not all of them are suitable for self-diagnosis of coronavirus.

Clip-on pulse oximeters

They are worn on the finger and are designed for one-time SpO2 measurement. These devices work on two AAA batteries.

In 2016, researchers tested six pulse oximeters of this type and concluded that, overall, they are not as accurate as blood gas tests done in hospitals. However, if a patient’s SpO2 is within the range of 90-100%, these devices were almost as accurate as blood tests. This means that pulse oximeters can be used for self-checks in case of coronavirus disease.

Manufacturers are required to register clip-on pulse oximeters as medical devices and issue them registration certificates (RC). Therefore, before buying a device, it makes sense to check the selected device in the state register of medical devices. To do this, just go to the website of Roszdravnadzor and enter the name of the pulse oximeter in the search bar.

Pulse oximeters for continuous monitoring

These devices are also attached to the finger, with a cord that goes to a monitor bracelet. Such devices are designed for continuous SpO2 monitoring of bedridden patients and are worn without removal. This type of device is powered by electricity and typically lasts for 500 recharges. Pulse oximeters for continuous monitoring are registered as medical devices.

An experiment has shown that pulse oximeters with a bracelet can provide reliable readings, even when people are doing household chores. Moving still interferes with the SpO2 determination, so occasionally the device makes a mistake and provides an incorrect result.

Clothingpins type and bracelets have not yet been compared. Even if healthy people constantly move and do not lie still, it is still safer to use clothespin pulse oximeters for self-monitoring if they have Coronavirus disease.

Fitness trackers and smartwatches

Sports gadgets that are worn on the wrist are sometimes referred to as pulse oximeters in certain online stores. Some of these devices, such as the Apple Watch Series 6 or the CMS 50F pulse oximeter, do have sensors that enable SpO2 measurement. However, while the technology used to measure oxygen concentration in these smartwatches is similar to that found in clip-on pulse oximeters, they are not identical.

Apple has provided the most comprehensive information about its device. The watch’s back features both LEDs and sensors. Similar to pulse oximeters, the LEDs “shine” through the arteries. However, instead of passing through, the light reflects off the blood vessels and reaches the sensors, which then transmit the data to the app.

Apple is exploring the possibility of using smart watches for diagnosing and monitoring the condition of individuals with COVID-19. However, until the results of the research are available, it would be premature to rely on this device, as the measurements may not be precise.

The initial testing of smart watches equipped with SpO2 detection function is not encouraging. The Washington Post’s technology reviewer tested both the Apple Watch Series 6 and the Fitbit Sense, which are very similar to it, and obtained different results in each test, which did not match the readings from a pulse oximeter clip.

None of the smart watches with pulse oximetry features, including the Apple Watch Series 6, are classified as medical devices. Apple representatives state that smart watches are not meant for use in medical settings.

Similarly, smartphone apps are not suitable for monitoring COVID-19 patients. In 2019, scientists downloaded three apps for measuring blood oxygen levels and put them to the test. The Oximeter and Heart Rate & Pulse Oximeter apps utilized the phone’s built-in camera, while the iOx app used a separate device with LEDs and sensors that functioned similarly to smart watches. This device had to be connected to the phone. Researchers compared the app data to results from a hospital SpO2 monitor and concluded that none of the apps provided accurate readings.

How to check the quality of a pulse oximeter

Pulse oximeters are available at varying price points. High-end pulse oximeters cost more than $300 and typically deliver accurate readings even in unfavorable conditions.

On the other hand, low-cost pulse oximeters fall into two categories: those that work well and cost less than $130 and those that provide inaccurate readings and are also cheap. The reliable inexpensive ones shut off automatically if the measurement conditions are unfavorable, while the unreliable ones give inaccurate readings in such conditions.

You can conduct a simple test to distinguish between the two types. By lifting the finger with the pulse oximeter above the head during the measurement, a reliable pulse oximeter will turn off at a specific point, while an unreliable one will display a falsely low saturation value.