Core_Equations_in_Respiratory_Phys5

Core_Equations_in_Respiratory_Phys5 - Nora Laiken, PhD CORE...

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Nora Laiken, PhD CORE EQUATIONS IN RESPIRATORY PHYSIOLOGY 1 1. Ideal gas law: PV = nRT Related laws: A t c o n s t a n t T : P 1 V 1 = P 2 V 2 (Boyle’s law) A t c o n s t a n t P : V 1 / V 2 = T 1 / T 2 (Charles’ law) 2. Partial pressure vs. concentration relationships: a. In a gas phase : P G = F G P (Dalton’s law) P G = partial pressure of gas G F G = fractional concentration of gas G P = t o t a l g a s p r e s s u r e b. In moist inspired gas : PI G = FI G (PB – PH 2 O) PB = barometric pressure P H 2 O = water vapor pressure ( always 47 mmHg at body temperature) Important application: PI O 2 = FI O 2 (PB – PH 2 O) When breathing air, F I O 2 = 0.21, regardless of altitude c. In a liquid phase : C G = kH G P G (Henry’s law) kH O 2 = 0.003 ml O 2 /100 ml blood · mmHg k H CO 2 = 0.067 ml CO 2 /100 ml blood · mmHg = 0.03 mmol CO 2 /liter blood · mmHg 3. Relation between alveolar ventilation (V . A) and total ventilation (V . T): V . A = V . T – V . D V . D = dead space ventilation or V . A = nVT– nVD n = breathing frequency V T = tidal volume V D = dead space volume 4. Diffusion equations: a. Fick’s law of diffusion (applied to the transfer of gas G from alveolar gas pulmonary capillary blood): V . G = (A/T) · D G · (PA G – Pc G ) V . G = rate of transfer of gas G from alveolar gas pulmonary capillary blood A = area of blood-gas barrier T = thickness of blood-gas barrier D G = diffusion constant of gas G (proportional to
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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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Core_Equations_in_Respiratory_Phys5 - Nora Laiken, PhD CORE...

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