pulse oximetry: purpose, uses and reading

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introduction

Pulse oximetry is a painless and non-invasive test that is used to measure the level of oxygen in your blood and how well it is being carried to other parts of your body like the arms and legs.

The device used to conduct this test is known as a pulse oximeter. Not many of us know that a pulse oximeter is not a newly invented device, though it has gained quite a bit of attention currently during the recent pandemic.

These oxygen metres have been around for more than 50 years and have proven to be a critical tool for assessing and tracking blood oxygenation levels in people with chronic lung and heart diseases. They are usually a part of a medical setting and are used by doctors and their teams as a monitoring and assessment tool.

The COVID 19 pandemic and its effect on people’s oxygen saturation levels and lung function have led more and more people to use pulse oximeters with every home having at least one of these devices. During the pandemic, this device revolutionized the ability to monitor a patient’s oxygen levels accurately and constantly and saved many lives.

A pulse oximeter is a tiny handheld device that is placed on your fingertip, which estimates the oxygen saturation of hemoglobin in the arterial blood. It consists of a monitor with a display board, a probe that has light-emitting diodes (LED), a photodetector, and batteries.

It works on the principle of light emission absorption of O2Hb. The trait of oxygenated hemoglobin is that it absorbs more infrared light and allows more red light to pass through. Then the pulse oximeter calculates the ratio of red light measurement and infrared measurement. This ratio is then converted to SpO2 and displayed on the screen.

what is the purpose of pulse oximetry?

Pulse oximetry is so commonly used in medical care that it is often referred to as the fifth vital sign besides pulse rate, body temperature, respiration rate, and blood pressure.

The main purpose of an oximeter reading is to measure the oxygen saturation of the blood indirectly as against a direct measurement that is done through a blood sample.

Several conditions affect lung function and blood oxygen levels. A pulse oximeter is used especially in conditions such as:

  • Pneumonia
  • Lung cancer
  • Asthma
  • Chronic Obstructive Pulmonary Disease
  • Anaemia
  • Congenital heart disease
  • COVID 19

In these situations, an oximeter reading becomes critical to:

Assess how you are reacting to your treatment.

Evaluate the efficacy of a ventilator.

Decide if someone needs help in breathing or supplemental oxygen therapy.

Assess if this supplemental oxygen therapy is effective or needs to be altered.

Evaluate and monitor oxygen levels after a surgery that required the patient to be sedated.

what are pulse oximetry reading ranges?

Before we understand pulse oximeter reading ranges, it is important to know how to get the most accurate readings. Whether you are in the hospital or using a fingertip pulse oximeter at home, there are some important guidelines that you should follow. Here is how to use pulse oximeter:

The most important thing is to invest in a quality device such as this one by Scure, Contec, which is not only easy to use but also gives reliable readings each time that you use it.

Sit upright and relax for at least 5 minutes without talking, moving, or walking.

Rest your hand on your chest. Keep it at the level of your heart.

Switch on the oxygen metre and clip it on your index finger.

Let the reading get steady. Keep it on in case the reading keeps fluctuating.

Since most oximeters also display pulse readings, you need to know how to read pulse oximeter.

Record the highest reading once it stops fluctuating for at least 5 seconds.

It is essential to note that certain things affect fingertip pulse oximeter readings. These include:

  • Dark nail paint
  • Measuring your blood saturation in cold surroundings
  • If you have a deformity in your finger
  • Skin pigmentation and thickness
  • Tobacco use immediately before or during your blood saturation measurement

This is how oximeter readings are organised:

Oxygen saturation (SpO2) %Observation
95 or moreNormal
90-94Acceptable
92 or lessAbnormal

what do pulse oximetry readings tell us?

For you to understand what your readings mean, it is essential for you to know how to read oximeter.

Here is how you can interpret the readings of your fingertip pulse oximeter:

When your pulse rate falls between 97-100 per cent, it is considered to be healthy. Older adults have lower saturation levels as compared to younger adults. In this case and absence of any lung-impairing conditions, a saturation level of 95 per cent is considered to be acceptable.

If your blood oxygen level is 95 per cent, it is considered to be a typical value in healthy people and doesn’t indicate any problems.

A blood saturation of less than 92 per cent indicates low oxygen levels and hypoxemia.

If your blood saturation levels fall below 88 per cent consistently, you need to consult with your doctor immediately and seek medical attention.

It is important to note that these oximeter readings depend to a large extent on a person’s state of health and situations such as:

Those who are overweight or suffer from lung diseases, heart conditions, sleep apnea, asthma, etc. tend to have low blood saturation levels.

People undergoing chemotherapy treatments for cancer generally report low levels of blood saturation.

Smoking

Talking or moving while taking oximeter readings.

Being in an extremely cold climate and associated conditions of hypothermia and decreased peripheral perfusion.

takeaway

Pulse oximeter is a safe and non-risky device to measure your blood saturation levels. Still, these devices should be used practically and with caution. Your readings must be reported to your doctor immediately, especially when you are experiencing any of the above-mentioned health issues. This will help you get adequate and appropriate medical attention if and when required. 

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