Diffusing capacity: Difference between revisions

Revision as of 21:06, 1 September 2007

Revision as of 21:13, 1 September 2007

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(The asterisk should be read as a dot over the letter, which is used to denote [[rate]] in [[respiratory physiology]].)

J^*O2 is the uptake of oxygen (ml/min). P_AO2 is the alveolar partial pressure of oxygen. P_cO2 is the [[partial pressure]] of oxygen in the alveolar capillary. Thus, the higher the diffusing capacity DL, the more gas will be transferred across the alveolar-capillary membrane for a given gradient in partial pressure (or concentration) of the gas.

QUESTION: What do the above variables represent, specifically?

However, becauseBecause it is difficult to measure the capillary partial pressure of oxygen, [[carbon monoxide]] (CO) is used as the test gas to measure the diffusing capacity (Dlco). Because CO is so tightly bound to hemoglobin in the red blood cells, the partial pressure of CO in the capillaries is assumed to be zero. Thus,

:<math>D_LCO = \frac {J^*_{CO}}{P_{ACO}}</math>