![]() ![]() ![]() The difference is usually 2–5 mmHg lower in ETCO 2 than arterial CO 2 (PaCO 2). 10ĮTCO 2 is a reflection of metabolism, circulation, and ventilation, and is usually equal to arterial CO 2 if there is no ventilation perfusion mismatch. The graphic representation of expired CO 2 over time is termed capnography, and the waveform produced is a capnogram. ![]() When CO 2 diffuses out of the lungs in to the exhaled air it can be measured by a capnometer, which measures the partial pressure or maximum concentration of CO 2 at the end of exhalation. 8, 9 This is a much smaller gradient than that for O 2 (65 mmHg/8.7 kPa), but the diffusion of both gases is almost equal, because CO 2 is much more soluble and has a diffusion constant 20 times greater than O 2. The partial pressure of venous CO 2 is 46 mmHg (6.1 kPa) and the alveolar partial pressure of CO 2 is 40 mmHg (5.3 kPa) which gives a pressure gradient of only 6 mmHg (0.8 kPa). 2, 8 The right ventricle pumps the venous blood to the lungs, where diffusion of carbon dioxide across the blood gas barrier of the alveolar wall, interstitial fluid, and pulmonary capillary endothelium is governed by Fick's law of diffusion (see definitions). Aerobic cell metabolism produces CO 2, which diffuses out of the cell and into the tissue capillaries, where it is transported to the right side of the heart by the venous circulation. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |