BIOL 221 Study Guide - Final Guide: Heart Failure, Oxygen Therapy, Partial Pressure
11 Feb 2020
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Document Summary
Molecular weight and membrane thickness are inversely related to diffusion. Larger molecules (higher molecular weight) diffuse through the membrane more slowly than small ones. Membrane thickness is increased by emphysema, inflammation, pulmonary edema caused by left ventricular failure, pneumonia, and prolonged periods at high altitudes. Carbon dioxide is approximately 20 times more soluble than oxygen in water. Therefore, the effect of a decreased oxygen gradient is seen before the effect of a decreased carbon dioxide gradient. Oxygen therapy increases the oxygen gradient, thus allowing more oxygen to enter the blood, but does not affect the carbon dioxide gradient. Unfortunately, this can lead to an accumulation of carbon dioxide in the blood because oxygen therapy is often given when ventilation cannot increase enough to rid the body of carbon dioxide. Body temperature is held relatively stable and, therefore, plays little role in affecting diffusion.
