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Increasing breathlessness. Diagnosed with cardiomyopathy, heart failure.What is the correlation between oxygen saturation and dyspnea?

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Hi Doc! How come my oxygen sats are normal - usually around 98% and my breathlessness increasing. I am a retired nurse and was diagnosed with cardiomyopathy(DCM) 2002 and now in heart failure. I'm aware of the my body's functioning and its possible prognosis. I am well cared for by my medicos and on all the appropriate medications - and count myself as lucky. It's just that I don't understand the correlation of normal sats and dyspnoea. A fan often helps. Thanks a lot,
Posted Fri, 3 May 2013 in Heart Failure
Answered by Dr. Sukhvinder Singh 4 hours later

Thanks for writing to us.

Breathlessness is an abnormal unusual awareness of breathing and it is not synonyms with low oxygen saturation. A normal oxygen saturation but still feeling of dyspnea (breathlessness) is possible. This may be feasible in any pathological condition/ disease where there is a fall in saturation due to disease process.

In the natural history of the disease, to a large extent, the body will tend to maintain the saturation by doing extra work (like increasing the rate and depth of breathing) and this extra work will be felt as dyspnea or that abnormal feeling associated with breathing. Although body will be able to maintain that normal "minute ventilation" and normal oxygen saturation by doing extra work , but this extra work will be felt as dyspnea.

For example in Dilated cardiomyopathy as the left atrial pressure increases it causes congestion in the pulmonary capillaries leading to abnormal air exchange in your lungs. But the body will tend to compensate for this by increasing rate of breathing. The presence of extra fluid in interstitial space will also cause signals through stretch receptors to cause sensation of breathlessness.
This phenomenon can also be explained on the basis of low hemoglobin (that is anemia).

I hope I cleared this pathophysiological point to you. I'll be glad to discuss more on this, if required.

Warm regards

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