How to Use a Pulse Oximeter

How to Use a Pulse Oximeter
12 August 2022

How to Use a Pulse Oximeter

How to Use a Pulse Oximeter

If you have tested positive for Covid-19, your doctor might have given you a pulse oximeter to monitor your blood oxygen levels. Some people are more at risk of their blood oxygen saturation decreasing if they find it difficult to intake enough oxygen through breathing. 


You might feel more comfortable taking pulse oximeter readings and monitoring your heart rate, even if you haven’t been advised to by a doctor. Using a pulse oximeter is easy and anyone can do it. In this article, we’ll find out what is a good pulse oximeter reading, how to keep a pulse oximeter readings chart, and when you should seek medical advice.

How to use pulse oximeter

How does a pulse oximeter work?

Using a pulse oximeter is easier if you understand how it works. Haemoglobin is the molecule that carries oxygen in your blood. How much oxygen you have in your blood depends on how much oxygenated haemoglobin there is in your bloodstream. A pulse oximeter calculation is made using the saturation of oxygenated haemoglobin in your blood.

Pulse oximeter diagram

The pulse oximeter calculates the number of oxygenated haemoglobin in the blood by shining a light with different lightwaves through your finger and measuring how much light gets absorbed.

Discover exactly what a pulse oximeter is and how it works in detail in our blog.

A pulse oximeter doesn’t just have to be used on a finger, although this is the most common place we use them for convenience. It can also be used on a toe or earlobe. On babies, they can be used on the hand or foot, and on dogs, they are placed on ears, lips, and tongues.

The Nonin 2500 PalmSAT Pulse Oximeter is designed for flexible use with a variety of different adaptors including Finger Clip Sensors, Soft Sensors, Flex Sensors, Ear Clip Sensors, Forehead Sensors, and Flexiform II Sensors, and more. This means you can use it to measure pulse on a range of different sites on adults, children, and babies. Pulse oximeters like the Nonin 2500 are highly adaptable and have lots of different uses. 

How to Use a Pulse Oximeter

Preparing to Take a Reading

1. Wash your hands.

2. Take off any nail polish or false nails on the finger you intend to use.

3. Gather everything you need (your pulse oximeter, a pen, your record if you’re recording your readings, and a thermometer if you’re taking your temperature). This is so that you don’t have to move around and raise your heart rate while taking a reading.

4. Sit down and make sure your hands are warm to the touch.

5. Rest your hand on your chest for five minutes.

Taking a Reading

1. Switch the pulse oximeter on using the button on the front.

2. Attach the pulse oximeter to your middle or index finger by inserting it into the clip. Make sure your finger is all the way inside. You might want to lean your hand on a table or the arm of a chair because you will need to hold it still.

3. Watch the pulse oximeter readings fluctuate on the screen, this is normal as it establishes a reading. The SpO2 and the BPM will go up and down for a few seconds. 

4. Once the numbers stop changing record your SpO2 and BPM.

SpO2 is your blood oxygen level, and BPM is your heart rate. The screen will show these two numbers side by side and will look similar to this.

% SpO2
PR bpm

Recording your pulse oximeter readings in a table will help you to see if and how they change over time. This will help you to notice if things get worse or better and give you the opportunity to call your doctor as early as possible if it seems like something is wrong. Your record will also provide your doctor with useful information if you become unwell.

Try to take readings three times a day at the same time. You could set alarms for the times so you don’t forget or ask someone you trust to help you.

How to Read a Pulse Oximeter

What should the reading be on a pulse oximeter? The pulse oximeter normal range is between 95% and 100% SpO2. If your SpO2 is 93-94% it’s not an emergency but you need to let your doctor know. They might ask you to come in and have a proper examination. If your SpO2 is 92% or less it’s a sign of critically low blood oxygen and you will need immediate medical attention.

Use this pulse oximeter readings chart to determine whether your SpO2, BPM, and temperature readings need action:

spO2%BPMTemperatureActions
96%+40-10036.5-37.5°CNo action needed
95%101-10938°CContinue to monitor at home
93-94%10-13038.1-39°CCall 111 or your GP for advice on what to do
92% or less131+39°CCall 999 or go to A&E

There might be other signs that tell you you need medical attention. Be aware of how you feel in yourself and watch out for telltale signs that your body is struggling to get enough oxygen, even if you think you have a normal oximeter reading:

Call 111 or arrange to see your doctor if:

  • You feel more breathless and less well over time.
  • You feel unwell generally and as though something is not right.
  • Tasks like getting dressed and making food feel too difficult.
  • You get out of breath when doing simple things like going to the toilet.
  • Your SpO2 is 94% or below when lying down or resting and doesn’t increase in the next hour.

There are other signs that you could need medical help that you might not immediately associate with your blood oxygen. Call 111 or your GP if you:

  • Cough up blood.
  • Have cold sweats, or feel shivery or clammy.
  • Faint.
  • Develop a rash that doesn’t disappear when you roll a glass over it.
  • Urinate more or less than usual, or can’t urinate at all.
  • Become sleepy, confused, or restless.

Call 999 and seek immediate medical attention if:

  • It becomes suddenly much more difficult to breathe (for example, if breathing worsens over the course of an hour or less).
  • You find you can’t finish a short sentence without needing to draw breath again.

If you are self-isolating it’s important that a family member or someone you trust checks on you regularly. If you live by yourself arrange a regular phone call with someone and ask them to call you if you do not call at the scheduled time. Tell them to contact emergency services if they call and you don’t answer the phone at the scheduled time.

Having a regular phone call is a good idea even if you are self-isolating but live with people, as they will be able to hear your breathing more clearly over the phone and get a sense of whether your breathing is laboured.

How to apply a disposable pulse oximeter on an infant

How to Apply a Disposable Pulse Oximeter on an Infant

A baby’s finger is too small to use a clip-on pulse oximeter, so a larger body part is needed to get an accurate reading. Normally an infant’s foot, hand, thumb, or big toe is used. This is where a pulse oximeter like the Nonin 2500 is ideal as it can be used with a Flexi Sensor which is an adhesive strip that can be wrapped around the area for reading.

1. Clean the area for taking the reading, any substance with dark pigmentation such as nail polish or dried blood can lead to an inaccurate reading. Make sure the skin is dry before applying the Flexi Sensor.

2. Carefully wrap the Flexi Sensor around the area, for example, the foot, making sure there are no air bubbles and the wrap has full contact with the skin. Ensure the sides of the Flexi Sensor are directly opposite each other.

3. Turn on the pulse oximeter and wait for the numbers to stabilise to determine an average reading.

Caution When Using a Pulse Oximeter on an Infant

  • Movement such as crying, wiggling, or shivering can result in an inaccurate reading. The best way to deter too much movement is to keep the infant warm and encourage family involvement to keep the infant calm. Swaddling a baby will help to keep him or her calm. Don’t allow the infant to go to sleep if possible.
  • If extended SpO2 monitoring is needed, be sure to re-assess the site of the Flexi Sensor every two hours and watch for signs of irritation.
  • Don’t use the pulse oximeter on the same extremity as a blood pressure cuff. Normal blood flow is required for an accurate reading.
  • Bright light and infrared light can affect the accuracy of a pulse oximeter. If there are bilirubin or surgical lights present it’s a good idea to cover the site of the reading with a blanket.

How to Use a Nonin Pulse Oximeter

The Nonin PalmSAT 2500 Pulse Oximeter is made to be straightforward and easy to use. Using a range of Nonin sensors, it can be adapted to take a reading on a finger, toe, ear lobe, baby’s hand or foot, or forehead. 

The Nonin Pulse Oximeter: How to Use the PalmSAT 2500

Connecting a Sensor

Your sensor will come with specific instructions on how to use it. Connect the sensor to the Nonin PalmSAT 2500 with the logo facing upwards.

Positioning the Device

Check the device is positioned correctly so that you can take an accurate reading. You will know the device is in the right place if:

  • The Pulse Quality display is flashing green.
  • The Pulse Rate and SpO2 are displaying numbers.
  • The Pulse Quality reading is in time with the pulse rate for a minimum of ten seconds.

The Pulse Quality sensor will flash amber or red if the device isn’t in the right place indicating it needs to be repositioned.

Taking a Reading

Turn the device on using the On button. Follow the sets above to attach a sensor to the site for reading (usually a finger). Wait for the numbers on the screen to stabilise.

The Nonin PalmSAT 2500 can be set with certain pulse oximeter normal reading presets unique to the patient. It will emit an alarm sound and flashing amber or red light if a reading drops below or exceeds the preset readings. Find out how to set presets in the device’s manual.

This diagram explains the purpose of each button and feature on the display screen of the device:

Nonin 2500 PalmSAT diagram

Here’s a video explaining how to use and programme your Nonin PalmSAT 2500 Pulse Oximeter in more detail, you can also check out the Nonin brochure.

If your device doesn’t seem to be working you might be able to fix it yourself without needing to call customer service. Find out about troubleshooting your pulse oximeter in our blog.

How to Use a Pulse Oximeter

In this video, we’ll cover how to use a pulse oximeter, how to keep a pulse oximeter readings chart, and when you should seek medical advice.

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