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Old 05-01-2014, 10:10 PM   #13
Brandis
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Join Date: Jun 2009
Location: florida
Posts: 658

Height: 5'9"

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An interesting thing about the heart- it doesn't have the oxygen extraction reserve of skeletal muscle(it already uses almost all of the oxygen in blood it receives). The only way to increase its own oxygenation is to dilate the coronary arteries and to increase cardiac output, usually by increasing heart rate. This is counterproductive, because as you struggle to breathe during an asthma attack, you are already not getting enough oxygen. The muscles and the heart are saying they both need more O2, so the cycle increases, but the heart rate going excessively high has the opposite effect. As the heart rate becomes very fast, it has little time to fill with blood, and thus effectively limits the amount of blood being pumped through the body (bring on the fatigue). So your heart doesn't know that it is doing itself more harm than good. The good news is that the heart can get stronger, but you definitely need to get checked out to make sure you don't have other issues. I do not have asthma, but maybe if you got a decent doc to help, you could better control, and get some better exercise tolerance. Just be safe. Asthma attacks are serious, but I am sure you already know that!
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