Pulmonology
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Pulse oximeter
Also known as Oximeter, SpO2 monitor
A pulse oximeter is the clip placed on a fingertip to measure how much oxygen the blood is carrying, shown as a percentage. A reading of 95% or above is normal for most healthy adults.
In Pulmonology
The device shines red and infrared light through the fingertip and reads what emerges on the other side. Oxygenated and deoxygenated absorb the two wavelengths differently, and the ratio between them gives the oxygen saturation — written SpO₂. Because it reads only the pulsing component of the signal, it is measuring arterial blood specifically, and it needs a detectable pulse to work at all.
Getting a reading that means something
- Warm hands. Cold fingers reduce blood flow and give a low or absent reading.
- Remove nail polish and false nails, which block the light path.
- Rest the hand still — movement is a common cause of a false low reading.
- Allow it to settle for a minute rather than reading the first number shown.
Saturation is also less accurate at the extremes and on darker skin, where studies have found readings can overestimate true oxygen levels — a reason to treat a borderline number as a prompt for assessment rather than a reassurance.
Where this comes up
Pulmonology
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Related terms
- DyspnoeaDyspnea, BreathlessnessDyspnoea is the medical word for breathlessness: the uncomfortable awareness of having to work at breathing. It is a symptom rather than a diagnosis, and it comes as often from the heart or the blood as from the lungs.
- AsthmaBronchial asthma, DammaAsthma is a long-term condition in which the airways are inflamed and tighten in response to triggers, causing wheeze, cough, chest tightness and breathlessness that come and go. It is controllable in almost everyone with the right treatment used correctly.
- SpirometryLung function test, Breathing testSpirometry measures how much air you can breathe out and how fast, by blowing hard into a machine. It is the test that distinguishes asthma from COPD and tracks how well either is controlled.
- SepsisBlood poisoning, SepticaemiaSepsis is the body's response to an infection turning against its own organs, and it is a medical emergency. It can develop from any infection and worsens by the hour without treatment.
- HaemoglobinHemoglobin, HbHaemoglobin is the iron-containing protein inside red blood cells that binds oxygen in the lungs and releases it to the tissues. Its concentration in blood is the number used to diagnose anaemia.