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Pulse oximeters and how to use them

Approved by our Clinical team | Jan 29, 2021

You may have read in the news that having a pulse oximeter at home is beneficial. We’ve looked at why, when and how you would use one.

What is a pulse oximeter?

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A pulse oximeter measures how much oxygen the haemoglobin in your blood is carrying. This reading is called the oxygen saturation (SpO2) and is shown as a percentage. People with lung conditions may have lower blood oxygen levels than normal so a pulse oximeter can help to see if oxygen levels drop below safe levels and there’s a problem.

How does a pulse oximeter work?

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It works by measuring how much light is absorbed by the blood. The pulse oximeter shines a light through your fingertip. It then measures how much light is absorbed by the body and uses this measurement to calculate the percentage of oxygen in your blood.

How to use a pulse oximeter?

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Insert your finger into the oximeter, making sure it is well positioned and not too tight or too loose. Nail varnish or pigment on the finger, like henna, may affect the reading as the colour can absorb the light emitted from the oximeter. Remove nail varnish or use a finger without pigment on it. It’s not recommended to use your oximeter in bright sunshine or light as it could disrupt the infrared sensor.

How to read a pulse oximeter?

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The oximeter display will show the percentage of oxygen in your blood, for someone who is healthy the saturation level will be around 95-100%. Some models will also show your heart rate (pulse frequency), like the Beurer PO35 Pulse Oximeter.

Which finger is best for a pulse oximeter?

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You can use an oximeter on any finger, but the NHS recommends the middle or index finger. Keep it in place for at least a minute, as it takes time for the reading to steady.