Low oxygen levels


I have a question about low oxygen levels after exercise. I have sn ICD due to episodes of VT and I also have multifocal PVCs. I struggle with ongoing symptoms but try to exercise either walking or gym each day for 30 minutes. The recovery however is quite traumatic with increased symptoms which last about an hour. I noticed my oxygen  levels drop to around 89-91 during the recovery period. Do you think this is indicative of changes to my ejection fraction? I had an echo around 18 months ago. What is the norm? Any advice would be very helpful please.




Healthy lungs with normal circulation should give you a %PO2-sat of 97% or better

by crustyg - 2023-11-11 04:57:24

Leaving aside the esoteric stuff (high altitude, technical diving), you should be seeing 97% or better.  Anything less means that a) you have 'shunting' - blood going from R->L heart without passing through oxygenated parts of the lung, or b) that gas transfer in the lungs is impaired (but that doesn't get better when resting), or both.

A small amount of shunting is quite common - terminal bronchioles which connect the alveoli (where gas exchange actually happens) become closed off with tiny mucus plugs.  When I was in training the theory was that sighing is an automatic mechanism to force us to take a much deeper breath from time to time, which helps open up these tiny airways and restore full gas exchange.  Exercise has a similar function.  Coughing only clears the big upper airways.  Postural drainage (taught to the cystics) also helps.

I imagine that you feel pretty terrible with a %PO2 of 89% or so: it's an interesting challenge to medical students to see if they can breath-hold down to <94% (IIRC) - those rare ones who can, tend to become serious free-divers!

Damaged lungs often have areas where ventilation and blood flow are mismatched, which produces shunting.  It seems to me quite likely that *some* folk with long-Covid have significant amounts of shunting probably due to micro-clots - but that's just my supposition.

If your %PO2-sat comes back up after exercise to something more normal then you have some sort of exercise-induced shunting.

You'll notice that I've not mentioned %LVEF (ejection fraction): IMHO this has nothing to do with reduced %PO2-sat.  *IF* you have a hole somewhere in your heart permitting R=>L blood flow that would cause shunting.  An intermittent PFO (quite common when looked for) would do it, especially if your lungs are relatively stiff and PA-pressure rises too much during exercise.  I doubt that a standard echo would spot an intermittent PFO.

multi focal premature ventricular contractions

by Gemita - 2023-11-11 07:40:10

Phil, If your symptoms have worsened since your last echocardiogram 18 months ago, I would certainly ask your doctor for another check of your ejection fraction/pumping action of your heart and to look for any adverse effects from the multi focal PVCs (like chamber enlargement).  I feel your oxygen levels are adversely affected by your PVCs.

Crustyg has provided some great information.  My husband is always “sighing” when he hyperventilates, and it is certainly nature’s way of helping him (and me) to control his breathing and to calm him down.

But getting back to you, I am not surprised that you have low oxygen levels with multi focal PVCs.  We have many PVC sufferers here, including me and I would be struggling too with multi focal PVCs which are clearly coming from so many sites.  I note you have an ICD to protect you in the event of a VT episode and I am sure your PVCs are not helping to keep you free from VT.  

Rhythm disturbances like PVCs can upset the timing of our pacemakers and some members have reported much lower heart rates (below their base rate) as a result, and lots of nasty symptoms too that required treating.  One member reported low oxygen levels too I recall.  

A couple of questions.  I wonder if oxygen therapy might help at times of distressing symptoms and whether you have sleep apnea?  It seems you need help to control your PVCs and your treatment so far is proving ineffective.  I know you have had several ablations.  Are you on any new meds or specific pacing therapies that might help with the PVCs?  Maybe they need to look at treatments again to improve your quality of life.  I expect they have checked electrolytes, thyroid and done the usual investigations for troublesome PVCs (like looking for CAD/ischaemic heart disease).   You could ask for another stress test and let them see what is happening.  Try to keep well hydrated and I hope things improve for you quickly.

recovery after exercise.

by Selwyn - 2023-11-11 15:58:43

The norm is as stated by crustyg.  It may be that your pacemaker rate response needs to be extended to clear your oxygen debt. You would know this my seeing how quickly your pulse settles to the resting rate after exercise. If your pulse settles within a minute, you are probably in need of lengthening the recovery period. Mind you, having said that 89% is very low and an hour of recover is nothing to do with your pacemaker settings, so the rate response is probably irrelevant.

Lung disease, heart disease, smoking, anaemia, peripheral vascular disease, Raynaud's Syndrome, tremor, can all contribute to oximeter  low readings. I have sometimes found instrument error to be a problem.  It is certainly worth trying the other arm's finger.

An hour of distress  to recover from half an hour of exercise is too long. This would indicate some sort of  illness. It would be best to seek a medical opinion. 

Low oxygen levels

by Philli1 - 2023-11-11 16:42:00

Thanks crusty, gemita and selwyn for your responses and very helpful comments.

In answer to your question gemita I'm not having any drug therapy as to date nothing has been effective. I have been asked to consider amiodrone but I am resisting currently due to the potential nasty side effects. After unsuccessful ablations and all sorts of trial drug therapy my clinicians have run out of options I think. I have had lung function tests and ongoing blood tests from time to time. Certainly my sleep patterns impact the symptoms during the day but have no impact on what I feel after exercise. They are the same. I am managing to cope generally with the pvcs during the day but the symptoms after any exertion are troublesome. I have another checkup after Christmas and I will follow up again. Thanks again everyone for your great comments. 

You know you're wired when...

Your pacemaker interferes with your electronic scale.

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