#MSCOVID19: pulse oximetry


If you are single I suggest going to extraordinary lengths to protect yourself if you have to self-isolate with COVID-19.

You may have heard about the tragic death of a young surgical trainee who died alone at home from COVID-19 in Belfast last week. He probably died from pulmonary complications of COVID-19 that had gradually crept up on him and by the time he needed hospitalisation and ventilatory support he was probably too unwell to do anything about it. A big issue is that as you become hypoxic (lack of oxygen) your thought processes become clouded and your ability to make a judgement about your own health become erratic. 

I know of two close colleagues who self-isolated with COVID-19 and both of them developed severe exertional shortness of breath at the height of their infection. My one colleague said he could barely make it from his bed to the toilet due to shortness of breath. Fortunately, both have made a recovery now and are doing well.

A third colleague who has recently recovered from COVID-19 was bed-bound for two weeks and was on the verge of calling an ambulance, but decided against it. Fortunately, his wife is a GP and was monitoring him at home with a pulse oximeter, a device to measure how much oxygen is in your blood, that she uses for home visits. This colleague tells me that he did try and call 111 and after waiting 90 minutes hung-up. Waiting ninety minutes or longer for advice and to then be told to call an ambulance could be the difference between life and death.

When we do our ward rounds on patients with COVID-19 we don’t have to examine them, we mainly assess how well their lungs are functioning based on their oxygen saturation in their blood relative to how much oxygen they are getting, be it from room air (21% oxygen) or via a nasal cannula or face mask. When we use nasal cannula or a face mark we deliver oxygen at different flow rates and this is also taken into account.

In general, most people have an oxygen saturation rate above 94%. It does vary with age and altitude. It is relatively easy to measure yourself, but you need to have a pulse oximeter. In early COVID-19 pneumonia, exertional oxygen saturation levels fall first, i.e. if you attempt to walk or exercise and your blood saturation levels fall, for example, below 90% despite being normal at rest. This would indicate that your lungs are in trouble and that you probably need to go to hospital. People with COVID-19 can deteriorate very rapidly, i.e. within hours, so having an early warning system should help.

I wonder if the young surgeon above had been monitoring himself with a pulse oximeter and had notice that his exertional blood oxygen saturation levels dropped with exertion (walking in his home) he would have gotten himself to hospital and survived? 

I personally think the Government’s and NICE’s guidance on when to be admitted to a hospital is potentially dangerous. The NICE guidance suggests using the following symptoms and signs to help identify who has more severe COVID-19 and may need admission to hospital: 

  • severe shortness of breath at rest or difficulty breathing 
  • coughing up blood 
  • blue lips or face 
  • feeling cold and clammy with pale or mottled skin 
  • collapse or fainting (syncope) 
  • new confusion 
  • becoming difficult to rouse 
  • little or no urine output

Can you imagine trying to pick these symptoms and signs up if you live alone and are self-isolated? I am sure self-monitoring of your peripheral blood oxygen saturation levels, in particular documenting their deterioration, will save lives during the COVID-19 pandemic. 

So after reading about the tragic case of the young surgeon dying alone at home, I purchased my own pulse oximeter online. It is an insurance policy for my family and any of my neighbours or friends who may get COVID-19 and have to self-isolate and self-monitor. I think the NHS or local communities should arrange for pulse oximeters to be dropped off for single people with COVID-19 who are self-isolating and given guidance on how to use them and at what point to call 999. I am sure home pulse oximetry will take some pressure off the 111 services and save lives. The sceptics will say that as home self-monitoring of oxygen saturations is an untested technology we would need to study this intervention first before recommending it at a population level. I would say bollocks. My sister has a progressive interstitial lung disease and is on 24-hour home oxygen therapy. She and her cohort of fellow patients all manage their home oxygen therapy using pulse oximeters. If she can use a pulse oximeter so can most people in the general population. In fact, technology companies should think about building pulse oximetry into the next versions of their smartwatches and make the technology ubiquitous.

Prof G tests out his pulse oximeter!

I am not saying that everyone should purchase a pulse oximeter, but if you are single and live alone without someone to monitor your status when you get COVID-19 it would be advisable to have one. I am convinced that my two colleagues who struggled through self-isolation at home would have been better off if they had known their own peripheral blood oxygen saturation levels, both on exertion and at rest. I suspect if they had they may. or at least one of them may, have been admitted to hospital for observation. 

Do you agree with me that we should add access to home pulse oximetry, particularly if you are single, to my list of things to do to prepare for getting COVID-19?

CoI: none

About the author

Prof G

Professor of Neurology, Barts & The London. MS & Preventive Neurology thinker, blogger, runner, vegetable gardener, husband, father, cook and wine & food lover.


  • I purchased one of these a few weeks ago for precisely the same reason. It seems like a very clear way of giving an indication (rather than guesswork on my or my partner’s condition) as to whether we need medical help. Because I’m not a medical professional though and there isn’t official guidance on this, it’s difficult to figure out what the cut-off reading is – is 90% the moment to seek help or is that leaving it late?

    Lots of these available to buy online it seems, and relatively cheaply for a reputable one.

    • It is important to get a baseline and then show a trend, i.e. a drop in saturation. If you give this information to the ambulance controller they will take you seriously. If you are worried don’t forget to also measure if after exertion; simple walking 10-20m is sufficient.

  • Don’t wait to long to seek help.
    This paper whilst not about MS suggests that we are staying at home too long to get help

    Reduced Rate of Hospital Admissions for ACS during Covid-19 Outbreak in Northern Italy. De Filippo et al.
    N Engl J Med. 2020 Apr 28. doi: 10.1056/NEJMc2009166. [Epub ahead of print].

    This paper is saying that fewer heart attacks are appearing in hospital and I could did out other papers saying the same thing about stroke. The implications are that some people are waiting too long to seek help and are dying at home as a consequence of this. Therefore as profG says it is vital that you seek help before it gets to a stage where you can’t.

  • Pulse oximetry not only detects worsening pneumonia it can also pick-up pulmonary emboli or clots which are not that uncommon in COVID-19 patients and one of the causes of delayed death. Sadly, one of our younger COVID-19 patients died of a massive pulmonary embolus on the general ward after being stepped down from ITU.

    • Please could you give a link to the exact pulse oximeter you bought online so that those of us who are not medical professionals can be confident we’re buying the correct tool? Thank you.

      • Just make sure the one you purchase is CE marked or FDA approved. These tell you that they are quality approved in the EU and/or the US, respectively.

        Prices differ widely; for example, you can get an all bells and whistles one that is run via a smartphone app using blue tooth or a cheap clip-on version. The latter is fine for what is needed.

        • I think a lot of people are getting the same idea and purchasing these pulse oximeters as I can’t find any in stock anywhere at the moment! Very best wishes to all.

    • I read it from cover-to-cover each week. Probably some of the best journalism on the planet, albeit it too neoliberal.

      • Me too, for nearly 15 years now.
        You can counter the neoliberal editorial line by reading The Spectator. I started doing so after the Brexit referendum to better understand that other point of view….it is quite enjoyable actually.

        • I read the Guardian for leftist views and the NY Times that is meant to cover the middle ground. However, recently the NYT has become an anti-Trump echo-chamber, which gets very boring.

  • I bought one about 5 weeks ago because I know the importance of monitoring oxygen levels in the blood with regard to chest infections etc and with Covid-19 being a respiratory virus it made sense to make a purchase.
    I do my stats every other day to check up on how things are looking, so far so good; temperature: 96.1, O2: 99, pulse: 80👍
    I agree everyone should have an oxymetre and they’re not expensive to buy – less than £30! I bought mine from a health group who deals with pulmonary disease.
    I certainly gives peace of mind as well as taking you temperature 😊

    Great advice Prof G

  • It seems a good plan to have at home a cheap piece of kit that can help distinguish between just feeling really rubbish and being dangerously unwell. Thank you for the suggestion.

  • I couldn’t agree more. My partner was seriously ill with pneumonia in December; without a pulse oximeter (he is trained in casualty care and is in a Mountain Rescue Team) he would have died at home. It was very scary as he is a fit fell runner in his late 40s. He got admitted to hospital on Boxing Day and is recovering. We do wonder if he had an early undocumented case of COVID-19.

    • You’re not the only person thinking this virus was here in the UK around Christmas time. The people I know were otherwise normally fit, suffering from an illness like nothing they had experienced before. Now they’re finding out the symptoms of non hospitalised patients, there’s a big question mark. The are all the types that wouldn’t seek medical advice when they fall ill. Another point, no one is telling us the normal death rate of people in care homes from seasonal illness or in the general population.

  • I live on my own and I agree we should self monitor. I’ve been checking for UTIs and blood pressure for years. I have a real problem with doctors, nurses and 111 operator believing my readings. I’ve been told I don’t have a temperature so I don’t have an infection and then the lab said I did. I’ve been asked have I been drinking after vomiting and feeling seriously ill post surgery from an infection. I know normally my stats run at 99% even though I only have 4 lung lobes. My biggest challenge should I be unlucky enough to contract Covid-19 is to convince a paramedic or doctor that there’s something seriously wrong.

    • Anonymous, yes, this is a big problem. GP said my partner had flu and sent him home a few days before Christmas without antibiotics. The first ambulance called after my 111 call at 1 am on Boxing Day was sent away by a duty doctor the paramedics had to consult with over the phone. Three hours later we had to call another ambulance! By that time he also had sepsis as well as pneumonia. All the paramedics were fantastic, but the hierarchy protocol nearly finished him off. Unfortunately our trust in GPs has plummeted further.

  • The New York Times had an article (which probably many of you have seen) discussing silent hypoxia in Covid 19 patients, where people were not having severe symptoms despite their blood oxygen saturation being low. And then all of the sudden becoming acutely and seriously ill with little warning . So even if you are not living by yourself it might be good to have an oximeter on hand.


    • It can’t tell if you have Covid-19. It can indicate that you may need oxygen therapy and need to go to hospital as I remember all too well when I had a pulmonary embolism.

By Prof G



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