Low pulse oximeter reading whilst lying on back

I have noticed that my SpO2 reading is sometimes low (about 92) when lying on my back. On sitting up or getting out of bed it quickly it rises to about 97. I have two different pulse oximeters, so I don't think this is a problem with the instrument. Is it normal for the reading to be affected by body position?

[CDreamer]

Yes. It’s quite normal for O2 sats to decrease during sleep or inactivity as your ability to absorb O2 is compromised when lying down - which is why with COVID you were advised to stay upright and active if you could and also why they proned very sick people. It’s very unlikely to be your machine.

I wouldn’t worry with sats of 92. If they fell below 92 and stayed there despite sitting or standing - then go see your doctor. My sats fluctuated widely during sleep and last night, according to iWatch which is only about 80% accurate I reckon - the range was 86-100%.

[Hidden in reply to CDreamer]

Now that I am walking about it's up to 98. My pulse was slow this morning (48bpm) and I have just read that if it's not strong the pulse oximeter might not detect very well. It could be that. Thanks for replying.

[etheral]

Agree with CDreamer. Worst case however would be fluid in your lungs caused by Congestive Heart Failure. If you feel short of breath lying down you should definitely see a doc ASAP. Best,etheral

[Hidden in reply to etheral]

I hope it's not that! Lungs feel ok. Thanks for replying.

[Barrick]

Hi I have long COVID and my O2 level also goes down to 89 -94 when I’m lying on my back. I have mentioned it to 2 cardiologists and they are not concerned. If I sit or stand it goes up to 98-99. My afib was dx after I had a mild case of COVID last august.

[Hidden in reply to Barrick]

It seems to vary according to which finger I use. I got 92, 93 and 94 just now. Thanks for replying.

[john-boy-92]

Do you have white finger syndrome that will affect your SpO2 readings? When lying down, it may be that your respiration rate drops and that reduces your SpO2. At least it recovers when you sit upright. When I've been in hospital and sat up in bed, on-the-ball doctors will get me talking and watch my SpO2 on the metrics monitor. If you're standing, an SpO2 of 92% would need attention, apart from the risk of passing out, 92% in an adult is the knee of the blood oxygen curve. Below 92% it will drop in a straight line. Fortunately my GP sent me straight to the respiratory hot clinic when my SpO2 was 76%.

[Hidden in reply to john-boy-92]

I don't think I have this. I know that if the temperature is low the device can be affected. I'll monitor over a few days to see if it changes. I've also ordered a new pulse oximeter in case the old one has developed a fault.

[john-boy-92]

With a low ambient temperature your body will tend to divert blood away from your hands and feet. Therefore your fingers can be like those for white finger syndrome (Raynald's disease). My index finger on one hand is worse than the rest of the fingers on that hand, and that hand is worse than the other. The readings on my home oximeter compare well with oximeters in hospital and, I invariably get asked if I have Reynauld's disease despite having healthy-looking pink fingers.