What is the purpose of a pulse oximeter? Role, operation

A pulse oximeter is a device that indicates oxygen saturation in the blood and pulse. It is used by health professionals but also at home. Discover its different uses.

What is a pulse oximeter?

A pulse oximeter or saturometer is a device that non-invasively measures blood oxygen saturation. and which indicates the pulse. This device is very frequently used in hospitals to monitor patients who have respiratory distress or who are on invasive or non-invasive ventilatory supports (oxygen therapy).

It is also useful in the GP’s office and at home to monitor if a person is not in respiratory distress. People with Covid-19 have been equipped with a pulse oximeter to monitor their oxygen saturation.

Composition

A pulse oximeter is composed of a sensor that is usually shaped like a housing, a monitor with a display, and a cable.

There are other models, reusable or not, of various shapes and consistencies:

  • rigid plastic finger or nose clips;
  • flexible fingering;
  • self-adhesive strips for the finger or hand (pediatrics), nose, or ear.

What is a pulse oximeter used for?

A pulse oximeter or saturometer makes it possible to measure in a simple, reliable, non-invasive, and continuous way the arterial saturation of hemoglobin. It transmits a light ray through tissues, most often a finger or toe in adults, but also the nose or earlobe, or the hand or foot in young children.

The value given by the pulse oximeter is called “Pulsed hemoglobin oxygen saturation, or SpO2”, to distinguish it from the measurement of hemoglobin saturation by arterial blood sampling (arterial saturation of hemoglobin with oxygen (O2), measured by blood gases (SaO2). It also indicates pulse and heart rate.

When is a pulse oximeter used?

A pulse oximeter is a method of screening and monitoring hypoxemia (a decrease in the amount of oxygen carried by the blood).

It is indicated for:

  • screening and monitoring of respiratory failure and hypoxemia in adults and children;
  • evaluation of the favorable response to oxygen therapy and/or prescribed therapies;
  • monitoring of an intubated patient or under general anesthesia.

The SpO2 measured with a saturometer is one of the vital parameters that is evaluated in consultation with consciousness, heart rate, blood pressure, respiratory rate, and temperature. This is one of the criteria for triage at the reception of emergencies.

Public concerned or at risk

A pulse oximeter is indicated for people whose oxygen level needs to be monitored, because they have a condition that affects oxygen (asthma, pneumonia, lung cancer, anemia, etc.) or because they have had surgery.) and those for which it is necessary to know if the oxygen therapy put in place is effective.

Covid-19 and pulse oximeter

The measurement of pulsed oxygen saturation (SpO2) on the finger is part of the medical assessment of the person who is a positive Covid-19 test.

Monitoring enhanced by a pulse oximeter (or saturometer) is indicated in patients:

  • whose age is greater than or equal to 65 years;
  • or have other risk factors for severe Covid-19;
  • or having respiratory signs.

This monitoring is carried out through self-monitoring or by a nurse.

How is a pulse oximeter used?

The operating steps

The sensor with a clamp shape is placed on the fingertips (index, middle, or ring finger) most often. It can also be attached to the earlobe, at the tip of the nose, to a toe, or under the soles of the feet. In newborns, the oximeter is placed in the upper right limb.

The oximeter screen then indicates the oxygen saturation in the blood as a percentage of SPO2 and the pulse in beats per minute.

Normal or abnormal oxygen saturation

The normal oxygen saturation for a healthy person is between 95% and 100% SpO2 (pulsed saturation measured with a pulse oximeter).

Below 95% the person is said to be in hypoxemia.

Normal arterial oxygen saturation (SaO2) is between 96% and 98% in a young adult and 95% in a person over 70 years of age.

Between 90 and 93%, the saturation is said to be mediocre.

When it is less than 90% the person is said to be in desaturation. This is hypoxemia. A “normal” SpO2 for a child is greater than 95%. A SpO2 level of less than 94% in a child is a criterion of severity and leads to hospitalization.

Precautions to be taken

Some precautions must be taken to obtain a reliable result:

  • the pulse oximeter must be well-positioned and the person must not move;
  • it should be used at room temperature because the cold can cause it to malfunction;
  • too bright a light in the room can also cause the device to malfunction;
  • Finally, nail polish, false nails, and certain chemicals on the hands can skew the results.

How to choose a pulse oximeter?

The pulse oximeter technique was invented in 1942 and used since the 1980s by American anesthesiologists in operating rooms and recovery rooms.

What are the criteria for choosing a pulse oximeter?

If you want to buy a pulse oximeter or saturometer, be sure to choose:

  • a product that has a certification (CE for example);
  • a small oximeter that is easy to carry anywhere but has a legible screen;
  • an oximeter adapted to the person (adult model or child model).

Choose models that keep data in memory and with an alarm system when the pulse or oxygen saturation is beyond standards.

Image Credit: Photo by cottonbro studio from pexels.com

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