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What is a pulse oximeter ?

A pulse oximeter is a small, portable medical device that measures blood oxygen saturation levels when placed on a person's finger or earlobe. This non-invasive medical device is a monitor that quickly determines how efficiently blood from the heart and lungs is being sent to the various organs of the body.

What does a pulse oximeter measure?

A pulse oximeter measures two things:
  • Blood oxygen saturation (SpO2): the measurement that indicates the percentage of saturated blood, being an estimate of the amount of oxygen that is being transported by red blood cells.
  • Pulse frequency: a Pulse rate is simply the heart rate which indicates the number of times the heart beats per minute.

How does a pulse oximeter work?

A pulse oximeter works on the principle of spectrophotometry, related to visible light. When the pulse oximeter is placed on the fingertip, toe or earlobe, it emits several small rays of light that pass through the blood in that specific part of the body.

Light sensors in the pulse oximeter measure the number of blood cells that carry oxygen and those that do not. It is observed that oxygenated blood is darker than deoxygenated blood. Therefore, the highly sensitive light sensors in the pulse oximeter detect variations in light absorption patterns between oxygen-carrying blood and oxygen-depleted blood, resulting in a reading.

Why is a pulse oximeter necessary?

A pulse oximeter is generally used to check how efficiently the heart is pumping oxygen around the body. Some patients are advised to use pulse oximeters to regularly monitor their blood oxygen saturation levels, which can often be affected by existing respiratory or heart problems. In these cases, you should keep a pulse oximeter on hand to check oxygen saturation levels whenever necessary.

Some of the medical conditions that can affect blood oxygen saturation levels include:

  • Chronic obstructive pulmonary disease (COPD)
  • Lung cancer
  • Asthma
  • Heart attack
  • Congenital heart defects (birth defects)
  • Pneumonia
  • Anemia

What can a pulse oximeter be used for?

In addition to determining blood oxygen saturation levels, pulse oximeters have many other uses that mainly include evaluating the effectiveness of a specific treatment. Here are some of the most common pulse oximeter uses:

  • To verify the effectiveness of a new lung medicine
  • To assess breathing difficulties
  • To monitor the oxygen levels of a ventilated patient
  • To assess oxygen levels during or after surgery with anesthesia
  • Evaluate the effectiveness of supplemental oxygen therapy if the patient is new to treatment
  • To determine the ability to tolerate increased physical activity
  • To monitor a person's breathing patterns during a sleep study in cases of sleep apnea

How to use a pulse oximeter?

The pulse oximeter is used both for continuous monitoring of hospitalized patients and for taking a single reading at the time of consultation. The steps involved during the procedure of using a pulse oximeter are as follows:

  • First, the pulse oximeter is placed on the person's finger or ear. Although this is a non-invasive test, the patient may feel slight pain or pinching due to the device clip.
  • Turn on the probe and within a few seconds the device will begin collecting accurate information and will display readings of blood oxygen saturation levels and pulse rate.
  • Once the reading is recorded, the probe can be removed and automatically turned off.
  • In some cases, the probe is left on for a certain period of time where continuous monitoring of oxygen saturation levels is necessary.

Understanding pulse oximeter readings:

Pulse oximeters generally display blood oxygen saturation levels as a percentage, represented by SpO2. While the pulse rate is displayed as a number ranging between 60 and 100, which indicates a normal heartbeat.

An SpO2 reading ranging between 95% and 100% is considered normal, while anything below 95% indicates underlying medical conditions that need to be evaluated immediately. Lower blood oxygen saturation levels may indicate the following health problems that need medical attention as soon as possible:

  • Breathing difficulties
  • Lung infection
  • Blocked airways
  • Poor blood circulation

Tips for getting accurate pulse oximeter results:

In general, pulse oximeter readings are accurate. However, there are some factors that can affect the functioning of the device and result in errors or inappropriate readings. Here are some things you should consider when using a pulse oximeter to get accurate results:

  • Make sure you place your finger correctly on the device
  • Sit still while reading
  • Position the probe correctly
  • Remove nail polish and avoid areas with tattoos
  • Warm up your fingers before starting the test
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