Facts You Need to Know about SpO2 Sensors

As health and safety become a top priority, individuals are identifying ways to manage their health at home. For example, medical devices such as pulse oximeters have become essential for personal health monitoring.

A pulse oximeter is a small, clip-like medical device attached to a body part, most commonly the finger. Pulse oximeter sensors (SpO2 sensors) use a non-invasive method to monitor a person's oxygen saturation (as opposed to measuring it directly through a blood sample). In addition, it can quickly detect small changes in oxygen levels.

Why do we use SpO2 sensors?

The oxygen level in our bodies is very important, and normal arterial oxygen saturation is 95-100%. Various disease states (such as heart failure, chronic lung disease, or sleep apnea) can reduce oxygen saturation. As a general rule, anyone with an oxygen saturation level below 89-90% will require supplementary home oxygen therapy to bring the oxygen saturation level back above 90%. In addition, suppose oxygen saturation levels fall into the mid-80s or low 70s. In that case, a variety of serious symptoms may occur, including visual changes, dizziness, changes in mental status, lack of consciousness, difficulty thinking, and other symptoms. Oxygen saturation levels below this level for long periods can be fatal.

Using SpO2 sensors to check changes in blood oxygen saturation over time can be used to monitor heart failure, chronic lung disease, or sleep apnea. This measurement helps to diagnose new problems and also helps to detect deterioration in these conditions before they become severe.

How do SpO2 sensors work?

SpO2 sensors involve a non-invasive method of monitoring a person's oxygen saturation, which measures the blood's percentage of oxyhemoglobin (oxygen-bound hemoglobin).

SpO2 sensors use the principle that oxyhemoglobin (oxygen-bound hemoglobin) and deoxyhemoglobin (not bound to oxygen) absorb light at different wavelengths differently.

The sensor device is placed on a thinner part of the patient's body, usually a fingertip, earlobe, or the foot of an infant. Through the body part, the device emits two wavelengths of light to a photodetector on the other side, which detects and measures the change in absorbance at each wavelength. Oxyhaemoglobin and deoxyhemoglobin absorb these two wavelengths of light in different ways. The device, therefore, detects the amount of oxyhemoglobin and deoxyhemoglobin in the arterial blood and displays this as the oxyhemoglobin saturation (SpO2), which is an indirect estimate of the arterial oxygen saturation (SaO2).

What are the types of pulse oximeter?

1. Finger pulse oximeter

A finger pulse oximeter is most commonly used at home. It is small, rectangular in shape, and clips onto the finger. There is a display located on the probe itself. It is usually used by clinicians, caregivers, or patients themselves to check oxygen saturation levels by sampling.

2. Hand-held pulse oximeter

This is mainly used by medical practices and hospitals as it is slightly more complex and provides more accurate readings. The probe is connected to a cable that is attached to the screen. To obtain a reading, the probe must be attached to a person's finger - preferably the index finger. This type of oximeter is used for spot checks but is also capable of continuously monitoring oxygen saturation. It is often used in hospitals, outpatient medical facilities, at home, or by EMS.

3. Tabletop Pulse Oximeter

This type is usually larger than the hand-held pulse oximeter. It can perform spot checks and continuous monitoring. Its size makes it ideal for hospitals, medical facilities, home care, and sub-acute environments.

4. Wrist-worn SpO2 sensors

This model is wireless and is typically used for continuous monitoring. Your doctor may wish to monitor your oxygen levels daily or while you sleep, making this model ideal. The instrument is designed to resemble a watch. A small wire connects a probe placed on your index finger to a small monitor on your wrist. The readings are displayed on this wrist monitor.

5. Pediatric pulse oximeter

Pulse oximeters for children are designed to fit snugly on small fingers. If the child has small fingers, some varieties can be attached to the foot or head and may work better.

What is a good pulse oximeter reading?

The oximeter will display two numbers. One is your blood oxygen level marked as SpO2. The other number is your heart rate. For most people, a normal blood oxygen level is 95% or higher; a normal heart rate is usually below 100. Your oxygen level and heart rate will vary depending on your activity, body posture, and general health.

The following section shows what an oxygen level reading means and when and how to seek medical attention.

1.90% or lower

This oxygen level is very worrying and may indicate a serious illness. Get to 911 immediately or go to the nearest emergency room right away. You may need an emergency X-ray or cardiac examination.

2.91% to 94%

This oxygen level is alarming and may indicate a medical condition. Call your healthcare provider immediately.

3.95% to 100%

This oxygen level is normal. Walk for two minutes and then measure your oxygen level again. If your oxygen level is below 95%, please follow the instructions in the relevant section above.

How to get accurate pulse oximeter readings at home?

1.Always follow the device manufacturer's instructions on how to take a reading.

2.Avoid taking readings under direct bright light.

3.It is best to read the test sitting down.

4.Make sure your hands are relaxed, warm, and below the level of your heart.

5.The hand should be stable and in a resting position.

6.It is best to use the middle finger of your right hand. Remove any nail polish from the finger you are using.

7.Insert your finger into the device and press the button to start the reading. Wait for at least 30 to 60 seconds until the reading stops changing and a stable number is displayed.


The market is flooded with many types of SpO2 sensors from different manufacturers. It is, therefore, the responsibility of physicians, biomedical engineers, and competent purchasers to determine the correct sensor to save the lives of the patients they are entrusted with.

It is crucial to buy from a reliable manufacturer with a transparent track record of the materials used in the manufacturing process and solid proof of positive reviews.

Unimed is a high-tech manufacturer specializing in medical monitoring consumables with international authoritative certifications and major market access qualifications such as FDA, CFDA, CE, FIME, CMEF, etc. The company covers a wide range of SpO2 sensors, which are compatible with almost all mainstream reusable and disposable SpO2 sensors on the market, such as the device of Masimo, Datascope, Nellcor, Nihon Kohden, Philips, and more.

If you need more information, please visit our website.

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