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.

Oxygen saturation is measured by a small, clip-like device called a pulse oximeter. An invaluable tool in clinics, hospitals and other medical settings, pulse oximeters help doctors provide their patients with outstanding medical 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?

If you’ve ever been admitted to hospital, or watched a medical documentary or drama, you’ve almost certainly seen a pulse oximeter. They are the small, clip-on devices that you see attached to patients’ fingertips. Non-invasive and completely painless, they measure the saturation of oxygen in a patient’s 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.

A drop in oxygen saturation can point to a serious issue with the circulatory or respiratory system. If a patient is in intensive care, or being treated for traumatic injuries, a sudden dip in the amount of oxygen in the blood is an important indicator that something is wrong.

The purpose of a pulse oximeter is to give doctors early warning of a potential oxygen saturation issues and allow them to properly monitor their patients. Using a pulse oximeter is now standard practice in most modern hospitals and clinics around the world.

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 calculations 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 a Pulse Oximeter Used to Measure?


A pulse oximeter is mainly used to take two important measurements: oxygen saturation and pulse rate. 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. Insufficient blood oxygen levels can cause a range of adverse health conditions including chest pain, shortness of breath and increased heart 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 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 the Purpose of a Pulse Oximeter?

 The purpose of a pulse oximeter is to measure the pulse rate and oxygen saturation of the blood. This information can tell doctors a number of things about their patient’s condition. For example, these readings can be used to assess how well a new lung medication is working, evaluate whether a person needs help breathing, decide how well mechanical ventilation is operating and monitor oxygen levels during or after a surgical procedure.

Pulse oximeter readings can help to determine the effectiveness of supplemental oxygen therapy and assess someone’s ability to cope with increased physical activity. They can also be used to check if someone temporarily stops breathing while they’re asleep, as in the case of sleep apnoea. 

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.

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.

The Rossmax Hand Held Pulse Oximeter SA210 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. 

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