Resp_symbols

Resp_symbols - From Essential Medical Physiology, Editor...

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From Essential Medical Physiology, Editor L.R Johnson, Elseivier/Academic Press, 3 rd edition, 2003 Physical and Chemical Principles in Respiratory Physiology Quantitative descriptions of gas exchange depend on relatively simple applications of the principle of conservation of mass, (or mass balance), and the ideal gas law using the symbols defined in Table 1. The symbols may appear complicated at first, but they are based on a few simple conventions. Primary variables are symbolized with a capital letter, and a dot over the variable indicates the first derivative with respect to time (eg, Q . = blood flow, or quantity of blood per unit time in L/min). Modifiers are small capitals for the gas phase (eg, V . A = alveolar ventilation) and lower case letters for liquid or tissues (eg, Pa = partial pressure in arterial blood). Finally, a specific gas species is indicated with a subscript (eg, Ca O 2 = O 2 concentration in arterial blood in mL O 2 /dL blood). The principle of conservation of mass is simply that matter is neither created nor destroyed. This principle was applied to physiologic transport by the German physiologist Fick in the last century. The F ick principle states that the amount of a substance consumed or produced by an organ is the difference between the amount of the substance entering the organ and the amount leaving the organ. To calculate whole body O 2 consumption (V . O 2 in mL/min), one measures the difference between the amount of O 2 inspired and the amount of O 2 expired from the lungs per unit time. The amount of O 2 inspired = V . • F I O 2 , where V . = ventilation (L/min) and F I O 2 = fractional concentration of O 2 in inspired gas (0.21 for room air). The amount of O 2 expired = V . • F E _ O 2 , where F E _ O 2 is the fractional concentration of O 2 in mixed-expired gas. If inspired ventilation equals expired ventilation, then: V . O
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This note was uploaded on 09/14/2011 for the course PHARM ps taught by Professor Staff during the Spring '11 term at UCSD.

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Resp_symbols - From Essential Medical Physiology, Editor...

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