Has a helpful friend told you to buy a pulse oximeter to monitor your asthma or your child’s asthma? Perhaps you have seen one for sale online or at the pharmacy and been tempted to buy it. Pulse oximeters have becoming increasingly popular due to COVID-19. But do you really need a pulse oximeter for asthma? The short answer is, not necessarily. A pulse oximeter can be useful tool in your asthma management plan, if you know how to use it properly and understand its limitations.
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What is a pulse oximeter and what does it measure?
A pulse oximeter is a medical device that usually clips to your fingertip. It works by shining light through your skin to measure the amount of oxygen in the blood. It also measures pulse. Oxygen saturation is often called SpO2. It is usually measured as a percentage, for example 98%.
A normal oxygen saturation for most people is usually 95-100%. If someone’s SpO2 level is lower than this, it may be a sign of worsening asthma. You should talk to your doctor about normal SpO2 levels for you as some conditions may affect this.
What do the experts say about using pulse oximeters at home?
A Cochrane review in 2015 found no evidence or studies to either support or refute use of pulse oximeters by asthma patients to self-monitor oxygen saturation. The review observed that patients should discuss using a pulse oximeter with their doctor. It also recommended these devices be used as part of an asthma management plan.
In Australia, the Therapeutic Goods Administration notes that using pulse oximeters at home “is safer and more effective when done as part of medical management, overseen by a doctor who will consider other factors when recommending treatment, and may be able to recommend a particular pulse oximeter for use“.1
Why we choose to use a pulse oximeter at home
Like us, you may have seen discussions in online forums where people insist that everyone with asthma or a child with asthma must have a pulse oximeter and that they can just grab a cheap one online. This goes against what our doctors and respiratory specialists advise.
We’ve discussed it with our doctor
We have chosen to have a pulse oximeter in our home first aid kit. This is something that our child’s respiratory specialist is aware of. We have had discussions about how to use one by reference to our asthma management plan. For us, a pulse oximeter is a useful tool to assist with monitoring when asthma is getting worse and we may need to go hospital. In our personal plane, an oxygen saturation less than 95% triggers us to see a doctor for a review and SpO2 <92% is our red flag. It also has come in handy when we’ve called an ambulance: the ambulance staff didn’t have a paediatric pulse oximeter on board and borrowed ours.
Experience and level of comfort
We also have a lot of practical experience monitoring oxygen saturation. Our child has had severe asthma requiring days of hospital admission and continuous monitoring. We have also done multiple overnight oximetry studies. This involved the hospital providing us with professional pulse oximetry equipment to take home and use for overnight sleep studies. We used the pulse oximeter to monitor for various breathing issues, including asthma, sleep disordered breathing and obstructive sleep apnoea. We did continuous oxygen saturation monitoring overnight together with written observations about sleep position, mouth breathing, wheezing, snoring and other details. By doing these sleep studies, we leant how to check if the pulse oximeter probe was attached properly and if readings were accurate. We also learnt more about the physical signs that happen when oxygen saturation drops lower than it should.
In other words, we are comfortable using a pulse oximeter and understanding its limitations. And we have discussed using on with our doctor, who has given us guidance on how to use it in conjunction with an asthma management plan.
Important limitations of using pulse oximeters for asthma
Pulse oximeters don’t always give an accurate reading. There are a number of things to know before you use one.
Use the right size
Older children and adults can use a standard fingertip pulse oximeter. Asthma New Zealand say that these are suitable for children greater than 30kg (about 9 years of age)2. Some devices will say that they are suitable for over 12 years of age.
Children who are younger than this should use a paediatric pulse oximeter, designed for smaller fingers. Very young children and babies need a different pulse oximeter: usually with a sensor on a tape that wraps around their finger (or toe).
Proper position
The best finger to use is the middle or index finger.
For a clip style pulse oximeter, open the device, place the fingertip all the way inside and gently close. If using a tape-on sensor, you need to make sure that the two sides of the sensor line up opposite each other on the finger.
To get an accurate reading, your hand should be at about waist level. And you need to keep your hand very still.
Watch the display on the monitor to see when there is a steady pulse and the SpO2 number is constant. If the readings aren’t consistent, check the position or try another finger. It can take a minute or two to get a proper reading.
Other possible problems
A pulse oximeter won’t get an accurate reading if fingers are too cold, so make sure they are warm enough first. You may need to rub your hands together.
There needs to be adequate blood flow (perfusion) to get good reading. Many pulse oximeters use a “plethysmograph” to measure this. The device will display heart beat in waves. If these waves have a good amplitude(are nice and high) then this shows good blood perfusion. If the waves are flatter the result might not be accurate.
The finger you clip the pulse oximeter to needs to be clean. There should be no nail polish or glitter on the finger nail as this can interfere with the light sensor.
Having very long finger nails or artificial nails can also interfere with the sensor placement and an accurate result.
The pulse oximeter itself needs to be clean and well maintained. We usually clean ours by wiping with disinfecting wipes. If it uses batteries, these need to be replaced when required. Most devices have a battery indicator, but if your readings seem unusually low, it’s a good idea to replace the batteries to be sure.
Pulse oximeters also may not work as well on darker skin with more pigmentation1.
Other signs of low oxygen and breathing issues
Don’t rely on technology alone to determine if you or your child are having difficulty breathing, have low oxygen saturation or need to seek medical assistance. It is more important to know the physical signs to look for.
What if the pulse oximeter is showing a very low SpO2 but your child looks fine and is breathing normally? It is far more likely that the pulse oximeter isn’t attached properly or isn’t giving an accurate reading. We’ve seen first hand when nursing staff know that their monitoring equipment is obviously giving the wrong reading. In that case they usually take an old fashioned manual pulse or heart rate instead. The same thing can happen with pulse oximeters. So knowing physical signs of breathing trouble is much more important than relying on your device to tell you. This is even more important if you are using a basic fingertip pulse oximeter that is not necessarily deigned for medical use. (Many cheaper models sold online say they are for sporting use only.)
If you have asthma and develop any of these symptoms, you should seek medical help promptly. These can be signs of low oxygen levels:
- shortness of breath, trouble breathing or increased coughing;
- you notice a bluish colour around you lips, face or your nail beds;
- feeling restless and uncomfortable;
- pain or tightness in the chest;
- very fast pulse2.
Children who are having trouble breathing might have “retractions”, where you can see the skin sucking in against their ribs or the base of their throat. This is a sign that they need urgent medical attention.
Asthma organisations strongly recommend written asthma management plans. Your plan should be your guide in managing asthma – including when to increase medications or seek medical attention.
What is the best pulse oximeter for asthma monitoring?
If after discussion with your doctor or specialist you do decide to invest to invest in a pulse oximeter:
- Ask your doctor what they recommend.
- Don’t just buy cheapest one you find. Like most things, you get what you pay for. There are dozens of cheap pulse oximeters available to purchase, but do your research to ensure that you find one that is reasonably accurate and reliable.
- Look for a device approved by the Therapeutic Goods Administration (Australia) or Food and Drug Administration (US), or the equivalent in your country.
- Buy the appropriate size pulse oximeter for the person you will be using it for. Most devices – especially fingertip pulse oximeters – are designed for adult use. If you are buying to monitor your child, make sure you get a children’s or paediatric size fingertip pulse oximeter for a child aged 2 – 12 years, or an oximeter with an infant sized probe for babies.
- Do you want to be able to do a spot check or have continuous monitoring? We have a fingertip monitor for spot checks. Other models can monitor continuously overnight.
Child pulse oximeter (fingertip)
Zacurate make a very popular fingertip pulse oximeter for children with a child friendly design. The cute little blue bear design is appealing to kids. It is small and portable and features adjustable brightness for the display, different display layouts to make it easy to read from different directions and plethysmograph display to check blood perfusion. It can measure pulse from 30 to 250 beats per minute and the accuracy for SpO2 is +/- 2% in the range from 70% to 100%. This pulse oximeter is suitable for children from age 2 to 12 (for spot checking and not for continuous use).
Adult pulse oximeter (fingertip)
If you like to record your health statistics using your smart phone, iHealth’s wireless pulse oximeter is a popular choice. Features include plethysmograph and prefusion index, a li-ion battery charged by micro USB and can be used with the iHealth Myvitals App to keep a log of your results to discuss with your doctor. It’s also compatibile with Apple Health which is great if you have an iPhone. This pulse oximeter has TGA approval in Australia (approved ARTG 226596) for use in adults. It is designed for spot checking and not for continuous use.
Pulse oximeter for infants and continuous monitoring
If you need continuous monitoring, there are some pulse oximeters available to the public that can do this. They are usually more expensive than the fingertip devices. Viatom (in Australia) and CMI (in the US) sell pulse oximeters with appropriate sized attachments for infants, children or adults as required.
The Viatom handheld pulse oximeter detects pulse, SpO2 and perfusion index on a large easy to read display and can record data for up to 580 hours. It also comes with software which allows you to produce reports to show your doctor. This pulse oximeter comes with attachments suitable for babies and adults.
In the US, CMI sell pulse oximeters for designed both continuous and spot checking for all ages – such as this rechargeable adult pulse oximeter.
If you buy online, check that the pulse oximeter is approved for use in your country, And don’t don’t forget to check if the device has the appropriate voltage/socket plug or if you will need to use an adapter.
References and more information
If you decide to invest in a pulse oximeter to use at home, remember that you should never rely on oxygen saturation readings alone in making decision about asthma management. Discuss with the doctor managing your asthma whether you should use one and how it fits with your asthma management plan.
For more information about pulse oximeters and asthma, see the following resources we’ve referred to in putting together this post:
- 1Therapeutic Goods Administration, “Limitations of pulse oximeters and the effect of skin pigmentation“, 7 January 2022
- 2Asthma New Zealand, “COVID-19 Positive: How to Use an Adult Oximeter” and “COVID-19 Positive: How to Pulse Oximeter in Children“
To learn more about how important it is to have a written asthma management plan, see our post – Asthma Action Plans: Practical Tool To Help In Asthma Management
*Disclaimer: Allergy Spot does not provide medical advice. You should always consult a suitably qualified medical practitioner in respect of your own medical conditions, symptoms or concerns. See our Website Terms for more details.
I also use an oximeter due to asthma. I’m curious as to why the study showed that it wouldn’t make a difference. If my oxygen is low I feel like that should be enough justified. Thanks for the tips, I had no idea about the nail polish.
Excellent! I agree with you, we cannot rely on technology only. Technology sometimes fails, we have to look at the patient’s signs and symptoms, too. Thanks!
Thanks so much, Dr Santiago – I appreciate your comments
Hi Jelissa.The Cochrane review was really saying that there haven’t been many studies on home use of pulse oximeters to say whether it is a good or bad idea for people to self-monitor. It sounds as though you find it a useful tool for managing your asthma too.