What is a Pulse Oximeter?

Measuring the oxygen saturation in a patient’s blood can tell a doctor a lot about their condition. In many cases, this measurement is an important indicator of the health of a patient and, if it drops, can be an early warning sign that something is wrong. Oxygen saturation is often regarded as a fifth vital sign, and monitoring levels of oxygen in the blood is now a standard part of patient care.

Today, we’re taking a closer look at these small but powerful devices and finding out exactly how pulse oximetry contributes to the diagnoses, treatment and outcomes of patients.

What is a Pulse Oximeter and What Does it Measure?

A pulse oximeter is a medical device used to measure the oxygen saturation level in the blood and pulse rate. They are the small, clip-on devices that you see attached to patients’ fingertips. If you’ve ever been admitted to hospital, or watched a medical documentary or drama, you’ve almost certainly seen a pulse oximeter. 

A pulse oximeter is mainly used to take two important measurements: 

Oxigen Saturation

Blood oxygen saturation is also known as SpO2. A SpO2 reading of 95% or more is generally considered to be normal. A SpO2 reading of 92% or less (at sea level) is an indicator that there’s not enough oxygen in the blood.  This is important as low oxygen saturation levels, also known as hypoxemia, can lead to a number of acute, adverse effects. If low oxygen levels are experienced for an extended period of time, it can result in long term damage to a number of organs and negatively impact the patient’s outcome.

Pulse Rate

Pulse rate is one of the most important vital signs doctors use when caring for their patients. Most pulse oximeters will display the pulse rate – also known as heart rate, or HR - in terms of beats per minute. A normal resting heartbeat should be between 60-100 beats per minute.

If a heart is beating more than 100 times per minute, it’s called tachycardia. A heart rate of less than 60 beats per minute is known as bradycardia. Both low and high pulse rates can be a sign that there’s something wrong.

What is the purpose of a Pulse Oximeter?

There are a number of reasons why a pulse oximeter might be required. These devices are commonly used to monitor patients when they are admitted to hospital. Even if their injury, disease or illness isn’t related to the respiratory or circulatory systems, it can still have an impact on blood oxygen saturation, so it’s important to keep a close eye on SpO2 readings.

Patients who have chronic lung conditions or heart disease will often be monitored using a pulse oximeter. In some cases, they’ll be given pulse oximeters to use at home so they can monitor their own pulse rate and SpO2 levels.

Conditions that commonly require a pulse oximeter include:

•      Chronic obstructive pulmonary disease (COPD)
•      Asthma
•      Pneumonia
•      Lung disease and cancer
•      Anaemia
•      Heart attack or heart failure
•      Congenital heart defects

How Do You Use a Pulse Oximeter?

A pulse oximeter works by attaching painlessly to the fingertip. Once in place, they send two wavelengths of light into the finger, one to check pulse rate and the other to check oxygen saturation. This process takes a matter of seconds to complete. The readings made by the pulse oximeter are then displayed on the monitor, or handheld screen, that comes with the device.

Pulse oximeters are used both for long-term patient monitoring and one-off checks. In some cases, they are also given to outpatients to use at home. This allows people living with chronic conditions to monitor their level of oxygen without visiting their doctor. 

 

What is PI on a Pulse Oximeter?

Some pulse oximeters also display a PI reading. PI stands for Perfusion Index and it shows how strong the pulse is at the point where the pulse oximeter is attached. A PI display will range from 0.02% for a very weak pulse to 20% for a strong pulse.

The higher the number, the better the blood flow to the fingertip. If the PI is persistently low, it could point to an issue with the patient’s circulation. Poor circulation can cause a number of problems, especially in the extremities. If a person has a low PI for an extended period of time, doctors will need to take action to help blood circulate more efficiently around the body.

What is a Pulse Oximeter Used For?

 

There are a number of reasons why a pulse oximeter might be required. These devices are commonly used to monitor patients when they are admitted to hospital. Even if their injury, disease or illness isn’t related to the respiratory or circulatory systems, it can still have an impact on blood oxygen saturation, so it’s important to keep a close eye on SpO2 readings.

Patients who have chronic lung conditions or heart disease will often be monitored using a pulse oximeter. In some cases, they’ll be given pulse oximeters to use at home so they can monitor their own pulse rate and SpO2 levels.

Conditions that commonly require a pulse oximeter include:

•      Chronic obstructive pulmonary disease (COPD)
•      Asthma
•      Pneumonia
•      Lung disease and cancer
•      Anaemia
•      Heart attack or heart failure
•      Congenital heart defects

What is PI on a Pulse Oximeter?

Some pulse oximeters also display a PI reading. PI stands for Perfusion Index and it shows how strong the pulse is at the point where the pulse oximeter is attached. A PI display will range from 0.02% for a very weak pulse to 20% for a strong pulse.

The higher the number, the better the blood flow to the fingertip. If the PI is persistently low, it could point to an issue with the patient’s circulation. Poor circulation can cause a number of problems, especially in the extremities. If a person has a low PI for an extended period of time, doctors will need to take action to help blood circulate more efficiently around the body.

How Accurate are Pulse Oximeters?

Pulse oximeters exhibit their highest level of accuracy when blood oxygen saturation falls within the range of 90% to 100%. As saturation levels decrease to between 80% and 90%, the accuracy of these devices diminishes. Their least accurate readings occur when saturation levels drop below 80%. It's important to note that readings may deviate by a few percentage points. For instance, if an FDA-cleared pulse oximeter indicates a saturation level of 90%, the actual oxygen saturation in the blood typically ranges between 86% and 94%.

In general, most individuals with good health maintain blood oxygen levels between 95% and 100%, although this range may be lower for those with lung-related conditions.

Why Use a Pulse Oximeter at Home?

 

If you have a disease or condition that affects your lungs, heart or circulatory system, your healthcare provider may ask you to use a pulse oximeter at home. Monitoring your blood oxygen saturation at home can help you keep an eye on your health without constant visits to the doctor.

Even people who don’t suffer from a chronic condition can benefit from having a pulse oximeter at home. Patients who are suffering from chest infections, and those concerned about COVID-19, can use a device to check SpO2 and pulse rate without visiting their doctor. If oxygen saturation falls, or their heart rate changes dramatically, it can be a sign that they need to seek proper medical care.

As an expert in healthcare we also recommend for patients with COPD to actively monitor their oxygen levels at home, especially between doctor visits. A pulse oximeter provides a convenient way to track oxygen saturation levels and identify any trends or fluctuations. By regularly monitoring and documenting these readings, patients can play a more active role in managing their condition and communicate effectively with their healthcare provider.

Which Pulse Oximeter Should I Buy?

There is a broad choice of pulse oximeters on the market. This makes it easy to find the device that’s right for you. Pulse oximeters come in two basic designs, one type has a separate display and fingertip clip and the other has the display integrated into the main body of the device. In general, integrated pulse oximeters are more affordable than those with separate clips and displays.

Pulse Oximeters for Home Use

If you need a pulse oximeter for home use, an integrated fingertip pulse oximeter is probably the best choice. These compact oximeters sit comfortably on the fingertip and have clear digital displays and easy to use interfaces. This type of pulse oximeter is readily available for around $100. The Rossmax Finger Pulse Oximeter SB100 and the A340 Dual Colour OLED Fingertip Pulse Oximeter from Aero Healthcare, are both good options if you’re looking for a compact device.

Pulse Oximeters for Children 

If you’re looking for a compact fingertip pulse oximeter for a child, Biolight Finger Pulse Oximeter is perfect. Lightweight, colourful and specifically designed for paediatric patients, it will help you to get accurate readings fast. The device comes with a convenient neck strap for hands free storage. This is especially useful when you’re out and about.

Pulse Oximeters for Long Term Monitoring

Although fingertip pulse oximeters are great for spot checks and home use, they’re often less versatile than devices with separate displays. If you need a pulse oximeter for long-term observation, a device with a separate handheld screen – or one that connects to a monitor – is ideal. Rossmax Hand Held Pulse Oximeter & Artery Check SA300 is a great option for hospital and clinical use or long term at home care. The device comes with an adult probe plus probes for neonatal and paediatric patients. It will give instantaneous warnings if readings fall outside the normal range and has a clear, backlit LCD screen. Commonly used in healthcare settings including emergency rooms, it’s one of the most trusted pulse oximeters around.

If you’d like to find out more about pulse oximeters, or explore our range of products, take a look at the Medshop website or get in touch with a member of our team today. 

 

Author: Steven John Cumper, B.App.SC. (Osteo.), M.Ost., is a businessman with a strong foundation in biomedical science and osteopathic medicine, who founded and led Medshop to international success, culminating in its acquisition by the Bunzl Group in September 2021, where he continues to serve as Managing Director (Medshop Group).