Pulse Oximetry - An Overview

Introduction:

Pulse oximetry is the test performed to measure the level of oxygen saturation in the blood. It is a simple and effective, painless procedure to measure the oxygen sent to other parts of the body, such as arms and legs, from the heart.

What Is Pulse Oximetry?

Pulse oximetry is an electronic device to measure the oxygen saturation in red blood cells. A pulse oximeter is an electronic device comprising a clip-like device attached to body parts such as the forehead, foot, ears, nose, and toes, most commonly fingers. It can be reused or disposed of. It actively detects even tiny changes in oxygen levels.

What Are the Purposes and the Uses of Pulse Oximetry?

The main purpose of pulse oximetry is to check if the blood is well-oxygenated. Pulse oximeters monitor the oxygen levels in certain medical conditions affecting blood oxygen levels. Certain medical conditions include:

• Asthma.

• Pneumonia.

• Lung cancer.

• Anemia.

• Chronic obstructive pulmonary disease.

• Congenital heart disease.

• Heart failure.

What Are the Indications of Pulse Oximetry?

• To assess the help of a ventilator.

• Check oxygen levels during or after a surgical procedure (performed under sedation).

• To determine whether someone needs breathing assistance.

• To check the effectiveness of the lung medication.

• To assess a person's capacity to tolerate increased physical activity.

• To evaluate whether a person needs supplemental oxygen therapy.

• To monitor the effectiveness of the supplemental oxygen therapy when a new treatment is followed.

• To evaluate whether the person stops breathing while sleeping, as in the case of sleep apnea performed during the sleep study.

What Are the Pros and Cons of a Pulse Oximeter?

Pulse oximeters have many advantages over traditional methods of measuring blood gas levels. For example, the traditional methods involve drawing arterial blood to measure the oxygen level, which takes at least 15 minutes to get the results. On the other hand, measuring oxygen levels with a pulse oximeter is a relatively painless method that yields immediate results.

However, the cons of pulse oximeter use include not giving an idea about the levels of other gases like carbon dioxide in the blood.

How to Measure the Reading?

• Pulse oximetry is used in both inpatient and outpatient settings.

• If required, a pulse oximeter is used in the home setting to keep track of oxygen saturation values.

What Is the Procedure Followed to Take a Reading?

• If the reading is taken from the finger, remove any jewelry or fingernail polish on the nails.

• Before starting the test, the hand should be warm, relaxed, and below the heart level.

• Keep the device on the finger, earlobe, or toes.

• Keep the device on for as long as needed to monitor pulse and oxygen saturation.

• Remove the device once the test is over.

• A small beam of light is passed through the blood in the finger to measure the oxygen levels.

• The readings are noted based on the amount of light absorbed by the oxygenated and de-oxygenated blood.

• The main advantage of the procedure is that it is non-invasive and painless.

• Pulse oximetry helps record the oxygen saturation level along with the heart rate.

What Are the Normal Readings of Pulse Oximetry Readings?

• According to the American thoracic society, normal pulse oximetry readings should be more than 89 percent.

• An oxygen saturation level of 95 percent is considered to be the most standard value for healthy people.

• The oxygen saturation below 92 percent is considered a deficient level of oxygen and indicates hypoxemic conditions.

• According to the food and drug administration, the prescription pulse oximeters record the value accurately with a slight variation of around four to six percent.

• When the saturation levels are measured with high-standard equipment, the value can be more accurate and precise.

• If the value is temporarily low below the normal level due to certain conditions, it does not cause significant damage to the cells.

• However, the repeated and consistent lowering of saturation levels may cause serious damage to the cells and indicate major health issues.

What Are the Steps to Be Followed After the Pulse Oximetry?

• Once the procedure is completed, the reading is available immediately, which helps evaluate whether other tests are necessary.

• The low readings may indicate the need for more oxygen and the necessity for supplemental oxygen therapy.

• If the pulse oximetry is present at home, the doctor advises when and how often the readings should be taken and the steps to manage the abnormal levels.

What Are the Different Types of Pulse Oximeters Used?

• Home Use: Pulse oximeters are commonly used at home during COVID- 19 pandemic. Since COVID -19 affects the lungs, it reduces the blood-oxygen levels. The pulse oximeters are classified into two types such as -

• Over-The-Counter Oximeters: These are commonly used oximeters. It is commonly available online and in stores. The design and quality vary individually. Some devices are designed in such a way that they can be linked to the smartphone app and record the values.

• Prescription Oximeters: These oximeters are most commonly used in hospital and clinic settings and are more expensive when compared to over-the-counter oximeters. These are available only with the prescription of the doctor. Follow the doctor's advice on usage and read the manual to use it correctly for a long duration. A proper reading is obtained only when:

• The hand should be relaxed and warm and below the heart level.

• Remove the jewelry and fingernail polish.

• Use the device according to the manual instructions given.

• Stick to one steady number (as the number keeps on changing initially).

• Keep track of the reading and note it down to show the readings in the subsequent follow-ups.

What Do the Results Mean?

• The oxygen saturation value below 90 % may show insufficient oxygen levels and indicate underlying problems associated with the lungs or the heart.

• If the oxygen levels are too low, overstrain of the heart or lungs are observed to reach enough oxygen, which is considered an indicator of organ dysfunction.

Conclusion:

Pulse oximetry is a non-invasive, painless procedure with no risks or side effects. The adhesives used in some probes may irritate the skin. However, the values are not as accurate as blood gas measurements for people with darker skin tones.