I had pulmonary edema due to the left side of the heart not pumping out into circulation an adequate volume of blood, and as a consequence the blood backed up into the lungs and fluids leak into the lung tissues. There is a sensation of not being able to get enough oxygen...it seemed identical of trying to breath through a heavy towel!
You may have a respiratory condition where there is some impedement to the oxygen exchange in the lungs or before. There is an instrument that can measure the oxygen content within the blood stream...it should be about 93% if I remember correctly.diaxide