Test 2 Study Guide Flashcards
The net movement of molecules from
an area of high concentration to an area of low concentration.
Diffusion
This process continues until the molecules are evenly distributed, reaching equilibrium.
Diffusion
An example of ___ ____ ____ is ventilation, in which mouth and alveolar pressure differences cause all air molecules to move together, in and out of the lungs.
Bulk Gas Flow
Creates a pressure gradient between the air outside the body at relatively
high pressure and the alveoli at relatively low pressure.
Bulk Gas Flow
The gas moves down the pressure gradient through the airways of the lungs
and into the alveoli until the pressure of the air and that in the alveoli are
equal in this process
Bulk Gas Flow
Gas moves from an area of high pressure to an area of low pressure in this process.
Bulk Gas Flow
States that the rate of gas transfer across tissue is directly proportional to the surface area of the tissue, to the diffusion constants, and to the difference in partial pressures of the gas between the two sides of the tissue.
Fick’s Law
Fick’s Law states that the rate of gas transfer across tissue is directly proportional to the ____ _____ of the tissue, to the diffusion constants, and to the difference in partial pressures of the gas between the two sides of the tissue.
Surface Area
This law summarizes the factors that determine the rate of gas diffusion
through the alveolar capillary membrane
Fick’s Law
Fick’s Law is inversely proportional to the ____ of the tissue
Thickness
Formula for Fick’s Law
Vgas = [A x D x (P1 – P2)] / T
A = surface area
D = diffusion coefficient (solubility)
(P1– P2) = diffusion gradient
T = membrane thickness
These conditions cause decreased alveolar surface area:
Atelectasis, alveolar fluid, emphysema,
secretions, pleural effusion
This causes decreased partial pressure gradient across the membrane:
High altitudes
These conditions cause increased alveolar thickness (diffusion path length):
Fibrosis, alveolar edema
What is the alveolar air equation?
PAO2 = PIO2 – PACO2 [FIO2 + (1 – FIO2/R)]
The number ____ in the alveolar air equation is a factor that adjusts for alteration in oxygen tension due to
variations in the respiratory exchange ratio.
1.2
States that the rate of diffusion of a gas through a liquid is directly
proportional to the solubility coefficient of the gas, and indirectly proportional to
the square root of the gram-molecular weight (GMW) of the gas.
Graham’s Law
Because O2 is a lighter molecule, it diffuses through a medium ____ times faster than CO2
.
1.17
GMW of CO2 = 44
GMW of O2 = 32
States that the amount of a gas that dissolves in a liquid at a given
temperature is proportional to the partial pressure of the gas.
Henry’s Law
The amount of gas that can be dissolved by 1 mL of a given liquid at 760 mm Hg
and specific temperature is known as the ____ _____ of the liquid.
Solubility Coefficient
CO2 solubility
0.592 = 24
O2 solubility
0.0244 = 1
_____ _____ means that the movement of gas across the alveolar wall is a
function of the integrity of the alveolar-capillary membrane itself.
Diffusion Limited
A strictly diffusion-limited test gas such as ____ _____ is used to measure the diffusion capacity of the lung.
Carbon Monoxide
Carbon Monoxide (CO) is used to measure diffusion capacity due to its high affinity for _____
Hemoglobin
Carbon Monoxide (CO) affinity for hemoglobin is ____ times greater than O2
210 times greater
As clinically performed, the single-breath CO test measures the amount (in
milliliters) of CO that diffuses across the alveolar-capillary membranes during a
___ second breath-holding period after first inhaling a known concentration of
CO.
10 second
Normal ranges for the single-breath CO test
20-30 mL/min/mm Hg
Normal DLCO in healthy young man under resting conditions
21 mL/min/mm Hg
Most O2 in the blood is bound to hemoglobin inside the ______
erythrocyte
Hemoglobin allows whole blood (plasma plus cellular components) to carry ____ mL/dL of O2 per 100 mL of blood if PaO2
= 100 mm Hg and Hb concentration = 15 g/dL.
20
