Chem Exam 3 Flashcards
alveolar gas equation
PAO2=FiO2 x (PB-PH2O(alveolar))-(PaCO2/RQ)
or
PAO2=FiO2 x (PB-47mmHg)-(PaCO2/.8)
what parts of the alveolar gas equation come from the ABG
PaCO2 and PaO2
alveolar arterial oxygen gradient
(PAO2-PaO2). normal 5-15mmHg
reasons for normal A-a difference
regional VA/Q mismatch (shunt), anatomic shunt of blood related to thesbian circulation or bronchial circulation
reasons for pathological A-a difference
anatomy shunt of blood related to PFO or intrapulmonary shunt
-alveolar-capillary membrane diffusion block
arterial-alveolar ratio
PaO2/PAO2. used for high FiO2. normal .75 or greater.
P/F ratio
PaO2/FiO2. <200 is ARDS
Henrys Law: for every 1mmHg of pressure applied, there is __________(O2)
.003ml of O2 dissolved in 100ml of blood
Henrys Law: for every 1mmHg of pressure applied, there is ________ (CO2)
.067 of CO2 dissolved in 100ml of blood
Oxygen Content Equation
CaO2=(SaO2 x Hgb x 1.34) + .003(PaO2)
Amount of oxygen delivered to tissue =
O2 content x CO
Daltons Law
total pressure of a gas is equal to the sum of the pressures of the individual gases in the mixture. r/t alveolar equation
Henrys Law
addresses dissolved oxygen. amount of gas dissolved in a liquid is directly proportional to the pressure applied to the gas that overlies the liquid
Henrys Law Equation
Cgas=Pgas/KH where Cgas is the dissolved gas concentration, Pgas is the partial pressure of gas above the liquid (represents gas molecules entering liquid). and KH is the solubility constant for a particular gas in a particular solvent (liquid). represents gas molecules LEAVING liquid.
KH
the higher the KH, the greater the tendency for gas to leave solution. thus, concentration of gas dissolved liquid would be lower and is inversely proportional to Kh
Boyles Law
at a constant temperature, pressure of gas is inversely proportional to volume. P1 x V1 = P2 x V2
Grahams Law
solubility over sq root of MW. CO2 is heavier than O2 and therefore will diffuse slower
Charles’ Law
at a constant pressure, volume of a gas is directly proportional to its absolute temperature. V1/T1=V2/T2
Boyles law PLUS Charles’ Law
dealing with constant number of moles of gas
P1 x V1/T1) = (P2xV2 /T2
Gay Lussacs Law
at a constant volume, the pressure of a gas is directly proportional to its absolute temperature
P1/T1=P2/T2
Ideal Gas Law
Combines Avogadro, Boyle, Charles, Daltons Laws
R=PV/nT where 760 x 22.4/1mole x273 = 62.36
Adiabatic Effect
a gas in a container which is isolated thermally from its environment becomes warmer when it is compressed and cools when it expands. Usually so rapid that heat liberation doesn’t have time to dissipate so you will feel it.