Thursday, 23 April 2020

When do you need to go to hospital? Can oximetry help?


I must admit I’m a bit slow on the uptake at times.

One of the legacies from my medical days is to have a pulse oximeter hanging around in my old medical bag. This tiny and relatively inexpensive gadget painlessly clips onto your finger and tells you your pulse rate and how saturated with oxygen your blood is. A month or so ago I ensured the batteries in mine are charged as I thought it might be useful with CODIV and left it at that. Until last night.  


Now the BBC comes in for a lot of stick, but they still shine, in particular the radio and more particularly, Radio 4’s ‘PM’ programme. I was half listening to an American physician, Prof Richard Leverton, who is working on the front line of COVID19 in Bellevue hospital in New York and was sharing his experiences from the front line. My ears pricked up. 

He pointed out a glaring hole in the current management of COVID.  While listening to this, the penny didn’t so much drop, as fell to the floor with a massive resounding CLANG! My gadget came to mind. 

Pulse oximetry is a simple, accurate and safe way of checking how you are doing when you have COVID, and in particular, when you are going to need oxygen. A big problem at the moment is that people are getting to hospital with severe disease and that is harder to manage, so more are needing ventilation and more are doing badly. How much better might it be to get to hospital early?

If you could know when your oxygen levels are dropping you might be well advised to call 111 and book yourself into a bed where you can get some oxygen. 

Listen to his interview HERE.

His story is also reported in the New York Times.

He told of patients arriving at hospital with O2 saturation levels less than 80% and as low as 50% who are critically ill who had languished for days at home while they deteriorated, along with their prognosis.  

The problems is that our familiar symptom of shortness of breath is caused by respiratory failure, when levels of CO2 in the blood increase and make you breath faster. You feel short of breath. With COVID, the oxygen levels drop and while you might be breathing faster, you might not feel the sensation of breathlessness and so just carry on at home until the pneumonia has become more severe and by implication your outcome worse.

Another important feature of oxygen in the blood is how it reduces when problems arise. It doesn’t slow get worse in a linear manner, once it drops, it drops more rapidly and this is why patient with COVID can suddenly deteriorate. 

The O2 saturation graph shows why: 



The famous O2 saturation curve shows saturation on the y axis and oxygen partial pressure on the X, that is the amount of oxygen being transported into your tissues as saturation falls. 

Don’t worry if you don’t understand this. The underlying message is simple.

As things start to deteriorate, they deteriorate more quickly. I listened to a doctor who had COVID speaking of how bad she felt when her O2 sat had dropped to just 93%. However, she felt awful with a fever, muscle pains and tiredness; she was not terribly short of breath. It was only because she could measure her O2 saturation that she was admitted to hospital early, had oxygen, did well and recovered quickly. Like Boris Johnson, this is the ideal.

Although there is no ‘hard’ research on the benefits of early intervention, it makes absolute sense. Indeed any trials looking at this would be, in my opinion, highly unethical. Prof Leverton ironically pointed out that anyone in the UK should get the same treatment as our own Prime Minister, he is absolutely right on so many levels!

Again, that is:

Early admission
Close monitoring
Careful treatment with oxygen. 
Stepping up treatment if needed.

So Johnson’s treatment was ideal. Get to a place where you can be monitored closely before you get too ill, ready for treatment to be stepped up if needed. He might have had more invasive monitoring, I don’t know, but knowing how much oxygen is in your blood with pulse oximetry is good enough for anyone in most situations and excellent out of hospital. 

A saturation monitor is far more useful than a thermometer and far more reliable than monitoring symptoms

I did a quick scan of the literature to find out what is known about predicting the severity of the illness. I found a Chinese article on the use of blood markers which might predict the need for ventilation, but they measure markers of severe illness. They are of little use, paradoxically, before you get to hospital. What is needed is a non-invasive test that can be done without the physical presence of a health care workers. This the saturation meter.

We need not wait for research. This is  a respiratory virus, it hits the lungs, is causes drops in oxygen in your blood, this can be measured accurately and cheaply. It can tell us when treatment is needed and can do so early.

When your oxygen saturation drops below 93%, call 111 and get to a place that can provide oxygen. Again, this would be Gold Standard, “Boris Johnson” treatment. Don’t wait for oxygen saturation to drop to 80% or lower by which stage you will have become critically ill. 

Could this have bigger implications?

Perhaps early treatment centres, like the Excel centre in London, could be used for providing bulk treatment with oxygen for those with O2 saturation less than 93%, who might not feel so unwell before they deteriorate and need  transfer to ITU. Ideally, both options would be provided in the same hospital. Prof Leverton felt that early treatment would reduce the need for ventilation. I agree.

So what now? I’ve bought another saturation monitor which I shall leave in the care of my family. I’ll copy this to the health correspondent at the Guardian, send it to my local MP asking him to fast track it to Matt Handcock, to Jon Ainsworth, the shadow Health Minister, to the wonderful Bart’s MS blog and feel free yourselves too, to spread this information around. Please do!

There are some monitors built into smartphones, but don't trust these, they are not accurate enough and inaccurate oxygen saturation readings can be dangerous.

Buy a monitor? I have. At the back of my mind, this is going to be the next big procurement issue. I hope so!




2 comments:

  1. I bought a pulse oxymeter about 5 weeks ago, with the same reasoning, to monitor my asthmatic wife, should the need arise. It cost about £10 from eBay - not a big investment! It works too (I tested it by hyperventilating for a while to purge CO2 and then holding my breath - you can see the level drop)

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    1. Hi Pete. Could you share it as widely as you can x

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